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Li H, Du Z, Zhu L, Zhang C, Xiong J, Zhou B, Dong B, Zhang X, Alifu N. Ultrabright NIR-IIb Fluorescence Quantum Dots for Targeted Imaging-Guided Surgery. ACS APPLIED MATERIALS & INTERFACES 2024; 16:32045-32057. [PMID: 38861701 DOI: 10.1021/acsami.4c04748] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2024]
Abstract
Pioneering approaches for precise tumor removal involve fluorescence-guided surgery, while challenges persist, including the low fluorescence contrast observed at tumor boundaries and the potential for excessive damage to normal tissue at the edges. Lead/cadmium sulfide quantum dots (PbS@CdS QDs), boasting high quantum yields (QYs) and vivid fluorescence, have facilitated advancements in the second near-infrared window (NIR-II, 900-1700 nm). However, during fluorescent surgical navigation operations, hydrophilic coatings of these inorganic nanoparticles (NPs) guarantee biosafety; it also comes at the expense of losing a significant portion of QY and NIR-II fluorescence, causing heightened damage to normal tissues caused by cutting edges. Herein, we present hydrophilic core-shell PbS@CdS@PEG NPs with an exceptionally small diameter (∼8 nm) and a brilliant NIR-IIb (1500-1700 nm) emission at approximately 1600 nm. The mPEG-SH (MW: 2000) addresses the hydrophobicity and enhances the biosafety of PbS@CdS QDs. In vivo fluorescence-guided cervical tumor resection becomes achievable immediately upon injection of an aqueous solution of PbS@CdS@PEG NPs. Notably, this approach results in a significantly reduced thickness (100-500 μm) of damage to normal tissues at the margins of the resected tumors. With a high QY (∼30.2%) and robust resistance to photobleaching, NIR-IIb imaging is sustained throughout the imaging process.
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Affiliation(s)
- Hui Li
- Department of Epidemiology and Health Statistics, School of Public Health, Xinjiang Medical University, Urumqi 830054, China
| | - Zhong Du
- The Second Affiliated Hospital of Xinjiang Medical University, Urumqi 841100, China
| | - Lijun Zhu
- The Second Affiliated Hospital of Xinjiang Medical University, Urumqi 841100, China
| | - Chi Zhang
- Department of Labor Hygiene and Environmental Hygiene, School of Public Health, Xinjiang Medical University, Urumqi 830054, China
| | - Jiabao Xiong
- The Second Affiliated Hospital of Xinjiang Medical University, Urumqi 841100, China
| | - Bingshuai Zhou
- State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun 130012, China
| | - Biao Dong
- State Key Laboratory of Pathogenesis, Prevention and Treatment of High Incidence Diseases in Central Asia, School of Medical Engineering and Technology, Xinjiang Medical University, Urumqi 830054, China
- State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun 130012, China
| | - Xueliang Zhang
- Department of Epidemiology and Health Statistics, School of Public Health, Xinjiang Medical University, Urumqi 830054, China
- State Key Laboratory of Pathogenesis, Prevention and Treatment of High Incidence Diseases in Central Asia, School of Medical Engineering and Technology, Xinjiang Medical University, Urumqi 830054, China
| | - Nuernisha Alifu
- Department of Epidemiology and Health Statistics, School of Public Health, Xinjiang Medical University, Urumqi 830054, China
- Department of Labor Hygiene and Environmental Hygiene, School of Public Health, Xinjiang Medical University, Urumqi 830054, China
- State Key Laboratory of Pathogenesis, Prevention and Treatment of High Incidence Diseases in Central Asia, School of Medical Engineering and Technology, Xinjiang Medical University, Urumqi 830054, China
- The Second Affiliated Hospital of Xinjiang Medical University, Urumqi 841100, China
- Engineering Research Center of Xinjiang and Central Asian Medicine Resources, Ministry of Education, Urumqi 830017, China
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2
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Li S, Hu F, Bi Y, Yang H, Lv B, Zhang C, Zhang J, Xiao M, Wang X. Micrometer-Scale Carrier Transport in the Solid Film of Giant CdSe/CdS Nanocrystals Imaged by Transient Absorption Microscopy. NANO LETTERS 2023; 23:9887-9893. [PMID: 37870769 DOI: 10.1021/acs.nanolett.3c02788] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/24/2023]
Abstract
For the practical applications in solar cells and photodetectors, semiconductor colloidal nanocrystals (NCs) are assembled into a high-concentration film with carrier transport characteristics, the full understanding and effective control of which are critical for the achievement of high light-to-electricity conversion efficiencies. Here we have applied transient absorption microscopy to the solid film of giant CdSe/CdS NCs and discovered that at high pump fluences the carrier transport could reach a long distance of ∼2 μm within ∼30 ps after laser pulse excitation. This intriguing behavior is attributed to the metal-insulator transition and the associated bandlike transport, which are promoted by the enhanced electronic coupling among neighboring NCs with extended wave functions overlap of the excited-state charge carriers. Besides providing fundamental transport information in the regime of high laser pump fluences, the above findings shed light on the rational design of high-power light detecting schemes based on colloidal NCs.
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Affiliation(s)
- Si Li
- National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Fengrui Hu
- College of Engineering and Applied Sciences, and MOE Key Laboratory of Intelligent Optical Sensing and Manipulation, Nanjing University, Nanjing 210093, China
| | - Yanfeng Bi
- National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Hongyu Yang
- Advanced Photonic Center, Southeast University, Nanjing 210096, China
| | - Bihu Lv
- Department of Scientific Facilities Development and Management, Zhejiang Lab, Hangzhou 311121, China
| | - Chunfeng Zhang
- National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Jiayu Zhang
- Advanced Photonic Center, Southeast University, Nanjing 210096, China
| | - Min Xiao
- National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
- Department of Physics, University of Arkansas, Fayetteville, Arkansas 72701, United States
| | - Xiaoyong Wang
- National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
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3
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Aryal S, Frimpong J, Liu ZF. Comparative Study of Covalent and van der Waals CdS Quantum Dot Assemblies from Many-Body Perturbation Theory. J Phys Chem Lett 2022; 13:10153-10161. [PMID: 36278936 DOI: 10.1021/acs.jpclett.2c02856] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Quantum dot (QD) assemblies are nanostructured networks made from aggregates of QDs and feature improved charge and energy transfer efficiencies compared to discrete QDs. Using first-principles many-body perturbation theory, we systematically compare the electronic and optical properties of two types of CdS QD assemblies that have been experimentally investigated: (i) QD gels, where individual QDs are covalently connected via di- or polysulfide bonds, and (ii) QD nanocrystals, where individual QDs are bound via van der Waals interactions. Our work illustrates how the electronic and optical properties evolve when discrete QDs are assembled into 1D, 2D, and 3D gels and nanocrystals, as well as how the one-body and many-body interactions in these systems impact the trends as the dimensionality of the assembly increases. Furthermore, our work reveals the crucial role of the di- or polysulfide covalent bonds in the localization of the excitons, which highlights the difference between QD gels and QD nanocrystals.
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Affiliation(s)
- Sandip Aryal
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, United States
| | - Joseph Frimpong
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, United States
| | - Zhen-Fei Liu
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, United States
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4
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Jasrasaria D, Weinberg D, Philbin JP, Rabani E. Simulations of nonradiative processes in semiconductor nanocrystals. J Chem Phys 2022; 157:020901. [PMID: 35840368 DOI: 10.1063/5.0095897] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
The description of carrier dynamics in spatially confined semiconductor nanocrystals (NCs), which have enhanced electron-hole and exciton-phonon interactions, is a great challenge for modern computational science. These NCs typically contain thousands of atoms and tens of thousands of valence electrons with discrete spectra at low excitation energies, similar to atoms and molecules, that converge to the continuum bulk limit at higher energies. Computational methods developed for molecules are limited to very small nanoclusters, and methods for bulk systems with periodic boundary conditions are not suitable due to the lack of translational symmetry in NCs. This perspective focuses on our recent efforts in developing a unified atomistic model based on the semiempirical pseudopotential approach, which is parameterized by first-principle calculations and validated against experimental measurements, to describe two of the main nonradiative relaxation processes of quantum confined excitons: exciton cooling and Auger recombination. We focus on the description of both electron-hole and exciton-phonon interactions in our approach and discuss the role of size, shape, and interfacing on the electronic properties and dynamics for II-VI and III-V semiconductor NCs.
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Affiliation(s)
- Dipti Jasrasaria
- Department of Chemistry, University of California, Berkeley, California 94720, USA
| | - Daniel Weinberg
- Department of Chemistry, University of California, Berkeley, California 94720, USA
| | - John P Philbin
- Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Eran Rabani
- Department of Chemistry, University of California, Berkeley, California 94720, USA
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5
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Ahn S, Vazquez-Mena O. Measuring the carrier diffusion length in quantum dot films using graphene as photocarrier density probe. J Chem Phys 2022; 156:024702. [PMID: 35032976 DOI: 10.1063/5.0071119] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
The diffusion length of quantum dot (QD) films is a critical parameter to improve the performance of QD-based optoelectronic devices. The dot-to-dot hopping transport mechanism results in shorter diffusion lengths compared to bulk solids. Herein, we present an experimental method to measure the diffusion length in PbS QD films using single layer graphene as a charge collector to monitor the density of photogenerated carriers. By producing devices with different thicknesses, we can construct light absorption and photocarrier density profiles, allowing extracting light penetration depths and carrier diffusion lengths for electrons and holes. We realized devices with small (size: ∼2.5 nm) and large (size: ∼4.8 nm) QDs, and use λ = 532 nm and λ = 635 nm wavelength illumination. For small QDs, we obtain diffusion lengths of 180 nm for holes and 500 nm for electrons. For large QDs, we obtain diffusion lengths of 120 nm for holes and 150 nm for electrons. Our results show that films made of small QD films have longer diffusion lengths for holes and electrons. We also observe that wavelength illumination may have a small effect, with electrons showing a diffusion length of 500 and 420 nm under λ = 532 nm and λ = 635 nm illumination, respectively, which may be due to increased interactions between photocarriers for longer wavelengths with deeper penetration depths. Our results demonstrate an effective technique to calculate diffusion lengths of photogenerated electrons and holes and indicate that not only QD size but also wavelength illumination can play important roles in the diffusion and electrical transport of photocarriers in QD films.
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Affiliation(s)
- Seungbae Ahn
- Department of Nanoengineering, Center for Memory and Recording Research, Calibaja Center for Resilient Materials and Systems, University of California San Diego, 9500 Gilman Drive, La Jolla, California 92093, USA
| | - Oscar Vazquez-Mena
- Department of Nanoengineering, Center for Memory and Recording Research, Calibaja Center for Resilient Materials and Systems, University of California San Diego, 9500 Gilman Drive, La Jolla, California 92093, USA
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6
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Shcherbakov-Wu W, Sercel PC, Krieg F, Kovalenko MV, Tisdale WA. Temperature-Independent Dielectric Constant in CsPbBr 3 Nanocrystals Revealed by Linear Absorption Spectroscopy. J Phys Chem Lett 2021; 12:8088-8095. [PMID: 34406780 DOI: 10.1021/acs.jpclett.1c01822] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Fundamental photophysical behavior in CsPbBr3 nanocrystals (NCs), especially at low temperatures, is under active investigation. While many studies have reported temperature-dependent photoluminescence, comparatively few have focused on understanding the temperature-dependent absorption spectrum. Here, we report the temperature-dependent (35-300 K) absorption and photoluminescence spectra of zwitterionic ligand-capped CsPbBr3 NCs with four different edge lengths (d = 4.9, 7.2, 8.1, and 13.2 nm). The two lowest-energy excitonic transitions are quantitatively modeled over the full temperature range within the effective mass approximation considering the quasi-cubic NC shape and nonparabolicity of the electronic bands. Significantly, we find that the effective dielectric constant determined from the best fit model parameters is independent of temperature. Moreover, we observe a temperature-dependent Stokes shift that saturates at a finite value of Δ ≈ 10 meV at low temperatures for d = 7.2 nm NCs, which is absent in bulk CsPbBr3 films. Overall, these observations highlight differences between the temperature-dependent dielectric behavior of NC and bulk perovskites and point to the need for a more unified theoretical understanding of absorption and emission in halide perovskites.
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Affiliation(s)
- Wenbi Shcherbakov-Wu
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139-4307, United States
| | - Peter C Sercel
- Center for Hybrid Organic Inorganic Semiconductors for Energy, Golden, Colorado 80401, United States
- Department of Applied Physics and Materials Science, California Institute of Technology, Pasadena, California 91125, United States
| | - Franziska Krieg
- Department of Chemistry and Applied Bioscience, ETH Zürich, 8093 Zürich, Switzerland
- Laboratory for Thin Films and Photovoltaics and Laboratory for Transport at Nanoscale Interfaces, Empa-Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland
| | - Maksym V Kovalenko
- Department of Chemistry and Applied Bioscience, ETH Zürich, 8093 Zürich, Switzerland
- Laboratory for Thin Films and Photovoltaics and Laboratory for Transport at Nanoscale Interfaces, Empa-Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland
| | - William A Tisdale
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
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7
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Lee H, Woo JY, Park DY, Jo I, Park J, Lee Y, Koo Y, Choi J, Kim H, Kim YH, Jeong MS, Jeong S, Park KD. Tip-Induced Strain Engineering of a Single Metal Halide Perovskite Quantum Dot. ACS NANO 2021; 15:9057-9064. [PMID: 33988975 DOI: 10.1021/acsnano.1c02182] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Strain engineering of perovskite quantum dots (pQDs) enables widely tunable photonic device applications. However, manipulation at the single-emitter level has never been attempted. Here, we present a tip-induced control approach combined with tip-enhanced photoluminescence (TEPL) spectroscopy to engineer strain, bandgap, and the emission quantum yield of a single pQD. Single CsPbBrxI3-x pQDs are clearly resolved through hyperspectral TEPL imaging with ∼10 nm spatial resolution. The plasmonic tip then directly applies pressure to a single pQD to facilitate a bandgap shift up to ∼62 meV with Purcell-enhanced PL increase as high as ∼105 for the strain-induced pQD. Furthermore, by systematically modulating the tip-induced compressive strain of a single pQD, we achieve dynamical bandgap engineering in a reversible manner. In addition, we facilitate the quantum dot coupling for a pQD ensemble with ∼0.8 GPa tip pressure at the nanoscale estimated theoretically. Our approach presents a strategy to tune the nano-opto-electro-mechanical properties of pQDs at the single-crystal level.
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Affiliation(s)
- Hyeongwoo Lee
- Department of Physics, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Republic of Korea
| | - Ju Young Woo
- Manufacturing Process Platform R&D Department, Korea Institute of Industrial Technology (KITECH), Ansan 15588, Republic of Korea
| | - Dae Young Park
- Department of Physics, Hanyang University, Seoul 04763, Republic of Korea
| | - Inho Jo
- Department of Physics, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Republic of Korea
| | - Jusun Park
- Department of Energy Science, Sungkyunkwan University (SKKU), Suwon 16419, Republic of Korea
| | - Yeunhee Lee
- Graduate School of Nanoscience and Technology, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Republic of Korea
| | - Yeonjeong Koo
- Department of Physics, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Republic of Korea
| | - Jinseong Choi
- Department of Physics, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Republic of Korea
| | - Hyojung Kim
- Department of Energy Science, Sungkyunkwan University (SKKU), Suwon 16419, Republic of Korea
| | - Yong-Hyun Kim
- Department of Physics, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Republic of Korea
- Graduate School of Nanoscience and Technology, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Republic of Korea
| | - Mun Seok Jeong
- Department of Physics, Hanyang University, Seoul 04763, Republic of Korea
- Department of Energy Engineering, Hanyang University, Seoul 04763, Republic of Korea
| | - Sohee Jeong
- Department of Energy Science, Sungkyunkwan University (SKKU), Suwon 16419, Republic of Korea
- Artificial Atom and Quantum Materials Center, Sungkyunkwan University (SKKU), Suwon 16419, Republic of Korea
| | - Kyoung-Duck Park
- Department of Physics, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Republic of Korea
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8
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Kim H, Nugraha MI, Guan X, Wang Z, Hota MK, Xu X, Wu T, Baran D, Anthopoulos TD, Alshareef HN. All-Solution-Processed Quantum Dot Electrical Double-Layer Transistors Enhanced by Surface Charges of Ti 3C 2T x MXene Contacts. ACS NANO 2021; 15:5221-5229. [PMID: 33635642 DOI: 10.1021/acsnano.0c10471] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Fully solution-processed, large-area, electrical double-layer transistors (EDLTs) are presented by employing lead sulfide (PbS) colloidal quantum dots (CQDs) as active channels and Ti3C2Tx MXene as electrical contacts (including gate, source, and drain). The MXene contacts are successfully patterned by standard photolithography and plasma-etch techniques and integrated with CQD films. The large surface area of CQD film channels is effectively gated by ionic gel, resulting in high performance EDLT devices. A large electron saturation mobility of 3.32 cm2 V-1 s-1 and current modulation of 1.87 × 104 operating at low driving gate voltage range of 1.25 V with negligible hysteresis are achieved. The relatively low work function of Ti3C2Tx MXene (4.42 eV) compared to vacuum-evaporated noble metals such as Au and Pt makes them a suitable contact material for n-type transport in iodide-capped PbS CQD films with a LUMO level of ∼4.14 eV. Moreover, we demonstrate that the negative surface charges of MXene enhance the accumulation of cations at lower gate bias, achieving a threshold voltage as low as 0.36 V. The current results suggest a promising potential of MXene electrical contacts by exploiting their negative surface charges.
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Affiliation(s)
- Hyunho Kim
- Materials Science and Engineering, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
| | - Mohamad I Nugraha
- KAUST Solar Center (KSC), Physical Science and Engineering Division (PSE), King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
| | - Xinwei Guan
- School of Materials Science and Engineering, University of New South Wales (UNSW), Sydney, NSW 2052, Australia
| | - Zhenwei Wang
- Materials Science and Engineering, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
| | - Mrinal K Hota
- Materials Science and Engineering, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
| | - Xiangming Xu
- Materials Science and Engineering, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
| | - Tom Wu
- School of Materials Science and Engineering, University of New South Wales (UNSW), Sydney, NSW 2052, Australia
| | - Derya Baran
- KAUST Solar Center (KSC), Physical Science and Engineering Division (PSE), King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
| | - Thomas D Anthopoulos
- KAUST Solar Center (KSC), Physical Science and Engineering Division (PSE), King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
| | - Husam N Alshareef
- Materials Science and Engineering, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
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9
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Maier A, Löffler R, Scheele M. Fabrication of nanocrystal superlattice microchannels by soft-lithography for electronic measurements of single-crystalline domains. NANOTECHNOLOGY 2020; 31:405302. [PMID: 32531775 DOI: 10.1088/1361-6528/ab9c52] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
We report a high-throughput and easy-to-implement approach to fabricate microchannels of nanocrystal superlattices with dimensions of ∼4 μm2, thus approaching the size of typical single-crystalline domains. By means of microcontact printing, highly ordered superlattices with microscale dimensions are transferred onto photolithographically prepatterned microelectrodes, obtaining well-defined superlattice microchannels. We present step-by-step guidelines for microfabrication, nanocrystal self-assembly and patterning to archive large quantities of up to 330 microchannels per device for statistically meaningful investigations of charge transport in single-crystalline superlattice domains. As proof-of-concept, we perform conductivity and field-effect transistor measurements on microchannels of PbS nanocrystal superlattices. We find that the electric transport within microchannel superlattices is orders of magnitude more efficient than within conventional large-scale channels, highlighting the advantage of the near single-crystalline microchannels presented in this paper.
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Affiliation(s)
- Andre Maier
- Institute of Physical and Theoretical Chemistry, University of Tübingen, Auf der Morgenstelle 18, D-72076, Tübingen, Germany. Center for Light-Matter Interaction, Sensors & Analytics LISA+, University of Tübingen, Auf der Morgenstelle 15, D-72076, Tübingen, Germany
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10
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Lee S, Choi MJ, Sharma G, Biondi M, Chen B, Baek SW, Najarian AM, Vafaie M, Wicks J, Sagar LK, Hoogland S, de Arquer FPG, Voznyy O, Sargent EH. Orthogonal colloidal quantum dot inks enable efficient multilayer optoelectronic devices. Nat Commun 2020; 11:4814. [PMID: 32968078 PMCID: PMC7511352 DOI: 10.1038/s41467-020-18655-7] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2020] [Accepted: 09/01/2020] [Indexed: 12/02/2022] Open
Abstract
Surface ligands enable control over the dispersibility of colloidal quantum dots (CQDs) via steric and electrostatic stabilization. Today’s device-grade CQD inks have consistently relied on highly polar solvents: this enables facile single-step deposition of multi-hundred-nanometer-thick CQD films; but it prevents the realization of CQD film stacks made up of CQDs having different compositions, since polar solvents redisperse underlying films. Here we introduce aromatic ligands to achieve process-orthogonal CQD inks, and enable thereby multifunctional multilayer CQD solids. We explore the effect of the anchoring group of the aromatic ligand on the solubility of CQD inks in weakly-polar solvents, and find that a judicious selection of the anchoring group induces a dipole that provides additional CQD-solvent interactions. This enables colloidal stability without relying on bulky insulating ligands. We showcase the benefit of this ink as the hole transport layer in CQD optoelectronics, achieving an external quantum efficiency of 84% at 1210 nm. The realisation of film made up of different compositions using colloidal QD inks remains a challenge because of redispersing of underlying films by polar solvents. Here, the authors introduce aromatic ligands to achieve QD inks in weakly-polar solvents that enable fabrication of multi-compositional films.
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Affiliation(s)
- Seungjin Lee
- Department of Electrical and Computer Engineering, University of Toronto, 35 St George Street, Toronto, ON, M5S 1A4, Canada
| | - Min-Jae Choi
- Department of Electrical and Computer Engineering, University of Toronto, 35 St George Street, Toronto, ON, M5S 1A4, Canada.,Department of Chemical and Biochemical Engineering, Dongguk University, Seoul, 04620, Republic of Korea
| | - Geetu Sharma
- Department of Physical and Environmental Sciences, University of Toronto Scarborough, Scarborough, ON, M1C 1A4, Canada
| | - Margherita Biondi
- Department of Electrical and Computer Engineering, University of Toronto, 35 St George Street, Toronto, ON, M5S 1A4, Canada
| | - Bin Chen
- Department of Electrical and Computer Engineering, University of Toronto, 35 St George Street, Toronto, ON, M5S 1A4, Canada
| | - Se-Woong Baek
- Department of Electrical and Computer Engineering, University of Toronto, 35 St George Street, Toronto, ON, M5S 1A4, Canada.,Department of Chemical and Biological Engineering, Korea University, 145 Anam-Ro, Seongbuk-Gu, Seoul, 02841, Republic of Korea
| | - Amin Morteza Najarian
- Department of Electrical and Computer Engineering, University of Toronto, 35 St George Street, Toronto, ON, M5S 1A4, Canada
| | - Maral Vafaie
- Department of Electrical and Computer Engineering, University of Toronto, 35 St George Street, Toronto, ON, M5S 1A4, Canada
| | - Joshua Wicks
- Department of Electrical and Computer Engineering, University of Toronto, 35 St George Street, Toronto, ON, M5S 1A4, Canada
| | - Laxmi Kishore Sagar
- Department of Electrical and Computer Engineering, University of Toronto, 35 St George Street, Toronto, ON, M5S 1A4, Canada
| | - Sjoerd Hoogland
- Department of Electrical and Computer Engineering, University of Toronto, 35 St George Street, Toronto, ON, M5S 1A4, Canada
| | - F Pelayo García de Arquer
- Department of Electrical and Computer Engineering, University of Toronto, 35 St George Street, Toronto, ON, M5S 1A4, Canada
| | - Oleksandr Voznyy
- Department of Physical and Environmental Sciences, University of Toronto Scarborough, Scarborough, ON, M1C 1A4, Canada.
| | - Edward H Sargent
- Department of Electrical and Computer Engineering, University of Toronto, 35 St George Street, Toronto, ON, M5S 1A4, Canada.
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11
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Tom AE, Thomas A, Ison VV. Novel post-synthesis purification strategies and the ligand exchange processes in simplifying the fabrication of PbS quantum dot solar cells. RSC Adv 2020; 10:30707-30715. [PMID: 35516046 PMCID: PMC9056350 DOI: 10.1039/d0ra05242f] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Accepted: 08/12/2020] [Indexed: 11/21/2022] Open
Abstract
Quantum dots (QDs) solids with iodide passivation are a key component for most of the well-performing PbS QDs solar cells. Usually, iodide passivation of oleic acid (OA) capped PbS QDs films is achieved by a solid-state ligand exchange process using tetrabutylammonium iodide (TBAI). This ligand exchange process has generally been reported to be incomplete, especially in higher thicknesses, affecting the properties of the films adversely, producing inconsistent results in the device structures fabricated. The present study is based on a systematic investigation of the TBAI exchange on PbS QDs films and the performance of the resulting solar cells. We could achieve a complete TBAI exchange in a sufficiently thick (∼240 nm) and dense QDs film deposited by a minimum number of coating steps, through the optimization of the number of post-synthesis washing cycles on the QDs. Detailed studies were carried out investigating the effect of the number of washing cycles on the quantity of OA before and after the exchange, the ligand exchange efficiency, the development of trap states and the resulting photovoltaic device performance. A power conversion efficiency of 5.55% was obtained for a device subjected to an optimum number of washing cycles. Quantum dots (QDs) solids with iodide passivation are a key component for most of the well-performing PbS QDs solar cells.![]()
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Affiliation(s)
- Anju Elsa Tom
- Centre for Nano-Bio-Polymer Science and Technology, Research and PG Department of Physics, St. Thomas College Palai Kerala-686574 India +919446126926
| | - Ajith Thomas
- Centre for Nano-Bio-Polymer Science and Technology, Research and PG Department of Physics, St. Thomas College Palai Kerala-686574 India +919446126926.,Research and Development Centre, Bharathiar University Coimbatore Tamil Nadu-641046 India
| | - V V Ison
- Centre for Nano-Bio-Polymer Science and Technology, Research and PG Department of Physics, St. Thomas College Palai Kerala-686574 India +919446126926
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12
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Dieleman CD, Ding W, Wu L, Thakur N, Bespalov I, Daiber B, Ekinci Y, Castellanos S, Ehrler B. Universal direct patterning of colloidal quantum dots by (extreme) ultraviolet and electron beam lithography. NANOSCALE 2020; 12:11306-11316. [PMID: 32421115 DOI: 10.1039/d0nr01077d] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Colloidal quantum dots have found many applications and patterning them on micro- and nanoscale would open a new dimension of tunability for the creation of smaller scale (flexible) electronics or nanophotonic structures. Here we present a simple, general, one-step top-down patterning technique for colloidal quantum dots by means of direct optical or electron beam lithography. We find that both photons and electrons can induce a solubility switch of both PbS and CdSe quantum dot films. The solubility switch can be ascribed to cross-linking of the organic ligands, which we observe from exposure with deep-UV photons (5.5 eV) to extreme-UV photons (91.9 eV), and low-energy (3-70 eV) as well as highly energetic electrons (50 keV). The required doses for patterning are relatively low and feature sizes can be as small as tens of nanometers. The luminescence properties as well as carrier lifetimes remain similar after patterning.
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Affiliation(s)
- Christian D Dieleman
- AMOLF, Center for Nanophotonics, Science Park 104, 1098XG Amsterdam, The Netherlands.
| | - Weiyi Ding
- AMOLF, Center for Nanophotonics, Science Park 104, 1098XG Amsterdam, The Netherlands.
| | - Lianjia Wu
- Advanced Research Center for Nanolithography, EUV Photoresists Group, Science Park 106, 1098 XG Amsterdam, The Netherlands.
| | - Neha Thakur
- Advanced Research Center for Nanolithography, EUV Photoresists Group, Science Park 106, 1098 XG Amsterdam, The Netherlands.
| | - Ivan Bespalov
- Advanced Research Center for Nanolithography, EUV Photoresists Group, Science Park 106, 1098 XG Amsterdam, The Netherlands.
| | - Benjamin Daiber
- AMOLF, Center for Nanophotonics, Science Park 104, 1098XG Amsterdam, The Netherlands.
| | - Yasin Ekinci
- Paul Scherrer Institute, Laboratory of Micro and Nanotechnology, Forschungsstrasse 111, 5232 Villigen, Switzerland
| | - Sonia Castellanos
- Advanced Research Center for Nanolithography, EUV Photoresists Group, Science Park 106, 1098 XG Amsterdam, The Netherlands.
| | - Bruno Ehrler
- AMOLF, Center for Nanophotonics, Science Park 104, 1098XG Amsterdam, The Netherlands.
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13
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Coherent Exciton Dynamics in Ensembles of Size-Dispersed CdSe Quantum Dot Dimers Probed via Ultrafast Spectroscopy: A Quantum Computational Study. APPLIED SCIENCES-BASEL 2020. [DOI: 10.3390/app10041328] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Interdot coherent excitonic dynamics in nanometric colloidal CdSe quantum dots (QD) dimers lead to interdot charge migration and energy transfer. We show by electronic quantum dynamical simulations that the interdot coherent response to ultrashort fs laser pulses can be characterized by pump-probe transient absorption spectroscopy in spite of the inevitable inherent size dispersion of colloidal QDs. The latter, leading to a broadening of the excitonic bands, induce accidental resonances that actually increase the efficiency of the interdot coupling. The optical electronic response is computed by solving the time-dependent Schrodinger equation including the interaction with the oscillating electric field of the pulses for an ensemble of dimers that differ by their size. The excitonic Hamiltonian of each dimer is parameterized by the QD size and interdot distance, using an effective mass approximation. Local and charge transfer excitons are included in the dimer basis set. By tailoring the QD size, the excitonic bands can be tuned to overlap and thus favor interdot coupling. Computed pump-probe transient absorption maps averaged over the ensemble show that the coherence of excitons in QD dimers that lead to interdot charge migration can survive size disorder and could be observed in fs pump-probe, four-wave mixing, or covariance spectroscopy.
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14
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Pan J, Li X, Gong X, Yin J, Zhou D, Sinatra L, Huang R, Liu J, Chen J, Dursun I, El‐Zohry AM, Saidaminov MI, Sun H, Mohammed OF, Ye C, Sargent EH, Bakr OM. Halogen Vacancies Enable Ligand‐Assisted Self‐Assembly of Perovskite Quantum Dots into Nanowires. Angew Chem Int Ed Engl 2019. [DOI: 10.1002/ange.201909109] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Jun Pan
- Division of Physical Science and Engineering (PSE)King Abdullah University of Science and Technology (KAUST) Thuwal, Jeddah 23955 Saudi Arabia
- College of Materials of Science and EngineeringZhejiang University of Technology Hangzhou Zhejiang 310014 P. R. China
| | - Xiyan Li
- Department of Electrical and Computer EngineeringUniversity of Toronto Toronto Ontario M5S 3G4 Canada
| | - Xiwen Gong
- Department of Electrical and Computer EngineeringUniversity of Toronto Toronto Ontario M5S 3G4 Canada
| | - Jun Yin
- Division of Physical Science and Engineering (PSE)King Abdullah University of Science and Technology (KAUST) Thuwal, Jeddah 23955 Saudi Arabia
| | - Dianli Zhou
- Division of Physical Science and Engineering (PSE)King Abdullah University of Science and Technology (KAUST) Thuwal, Jeddah 23955 Saudi Arabia
| | - Lutfan Sinatra
- Division of Physical Science and Engineering (PSE)King Abdullah University of Science and Technology (KAUST) Thuwal, Jeddah 23955 Saudi Arabia
| | - Renwu Huang
- Division of Physical Science and Engineering (PSE)King Abdullah University of Science and Technology (KAUST) Thuwal, Jeddah 23955 Saudi Arabia
| | - Jiakai Liu
- Division of Physical Science and Engineering (PSE)King Abdullah University of Science and Technology (KAUST) Thuwal, Jeddah 23955 Saudi Arabia
| | - Jie Chen
- Division of Physical Science and Engineering (PSE)King Abdullah University of Science and Technology (KAUST) Thuwal, Jeddah 23955 Saudi Arabia
| | - Ibrahim Dursun
- Division of Physical Science and Engineering (PSE)King Abdullah University of Science and Technology (KAUST) Thuwal, Jeddah 23955 Saudi Arabia
| | - Ahmed M. El‐Zohry
- Division of Physical Science and Engineering (PSE)King Abdullah University of Science and Technology (KAUST) Thuwal, Jeddah 23955 Saudi Arabia
| | - Makhsud I. Saidaminov
- Department of Electrical and Computer EngineeringUniversity of Toronto Toronto Ontario M5S 3G4 Canada
| | - Hong‐Tao Sun
- College of Chemistry, Chemical Engineering and Materials ScienceSoochow University Suzhou Jiangsu 215123 P. R. China
| | - Omar F. Mohammed
- Division of Physical Science and Engineering (PSE)King Abdullah University of Science and Technology (KAUST) Thuwal, Jeddah 23955 Saudi Arabia
| | - Changhui Ye
- College of Materials of Science and EngineeringZhejiang University of Technology Hangzhou Zhejiang 310014 P. R. China
| | - Edward H. Sargent
- Department of Electrical and Computer EngineeringUniversity of Toronto Toronto Ontario M5S 3G4 Canada
| | - Osman M. Bakr
- Division of Physical Science and Engineering (PSE)King Abdullah University of Science and Technology (KAUST) Thuwal, Jeddah 23955 Saudi Arabia
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15
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Pan J, Li X, Gong X, Yin J, Zhou D, Sinatra L, Huang R, Liu J, Chen J, Dursun I, El-Zohry AM, Saidaminov MI, Sun HT, Mohammed OF, Ye C, Sargent EH, Bakr OM. Halogen Vacancies Enable Ligand-Assisted Self-Assembly of Perovskite Quantum Dots into Nanowires. Angew Chem Int Ed Engl 2019; 58:16077-16081. [PMID: 31529587 DOI: 10.1002/anie.201909109] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2019] [Revised: 09/13/2019] [Indexed: 12/21/2022]
Abstract
Interest has been growing in defects of halide perovskites in view of their intimate connection with key material optoelectronic properties. In perovskite quantum dots (PQDs), the influence of defects is even more apparent than in their bulk counterparts. By combining experiment and theory, we report herein a halide-vacancy-driven, ligand-directed self-assembly process of CsPbBr3 PQDs. With the assistance of oleic acid and didodecyldimethylammonium sulfide, surface-Br-vacancy-rich CsPbBr3 PQDs self-assemble into nanowires (NWs) that are 20-60 nm in width and several millimeters in length. The NWs exhibit a sharp photoluminescence profile (≈18 nm full-width at-half-maximum) that peaks at 525 nm. Our findings provide insight into the defect-correlated dynamics of PQDs and defect-assisted fabrication of perovskite materials and devices.
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Affiliation(s)
- Jun Pan
- Division of Physical Science and Engineering (PSE), King Abdullah University of Science and Technology (KAUST), Thuwal, Jeddah, 23955, Saudi Arabia.,College of Materials of Science and Engineering, Zhejiang University of Technology, Hangzhou, Zhejiang, 310014, P. R. China
| | - Xiyan Li
- Department of Electrical and Computer Engineering, University of Toronto, Toronto, Ontario, M5S 3G4, Canada
| | - Xiwen Gong
- Department of Electrical and Computer Engineering, University of Toronto, Toronto, Ontario, M5S 3G4, Canada
| | - Jun Yin
- Division of Physical Science and Engineering (PSE), King Abdullah University of Science and Technology (KAUST), Thuwal, Jeddah, 23955, Saudi Arabia
| | - Dianli Zhou
- Division of Physical Science and Engineering (PSE), King Abdullah University of Science and Technology (KAUST), Thuwal, Jeddah, 23955, Saudi Arabia
| | - Lutfan Sinatra
- Division of Physical Science and Engineering (PSE), King Abdullah University of Science and Technology (KAUST), Thuwal, Jeddah, 23955, Saudi Arabia
| | - Renwu Huang
- Division of Physical Science and Engineering (PSE), King Abdullah University of Science and Technology (KAUST), Thuwal, Jeddah, 23955, Saudi Arabia
| | - Jiakai Liu
- Division of Physical Science and Engineering (PSE), King Abdullah University of Science and Technology (KAUST), Thuwal, Jeddah, 23955, Saudi Arabia
| | - Jie Chen
- Division of Physical Science and Engineering (PSE), King Abdullah University of Science and Technology (KAUST), Thuwal, Jeddah, 23955, Saudi Arabia
| | - Ibrahim Dursun
- Division of Physical Science and Engineering (PSE), King Abdullah University of Science and Technology (KAUST), Thuwal, Jeddah, 23955, Saudi Arabia
| | - Ahmed M El-Zohry
- Division of Physical Science and Engineering (PSE), King Abdullah University of Science and Technology (KAUST), Thuwal, Jeddah, 23955, Saudi Arabia
| | - Makhsud I Saidaminov
- Department of Electrical and Computer Engineering, University of Toronto, Toronto, Ontario, M5S 3G4, Canada
| | - Hong-Tao Sun
- College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou, Jiangsu, 215123, P. R. China
| | - Omar F Mohammed
- Division of Physical Science and Engineering (PSE), King Abdullah University of Science and Technology (KAUST), Thuwal, Jeddah, 23955, Saudi Arabia
| | - Changhui Ye
- College of Materials of Science and Engineering, Zhejiang University of Technology, Hangzhou, Zhejiang, 310014, P. R. China
| | - Edward H Sargent
- Department of Electrical and Computer Engineering, University of Toronto, Toronto, Ontario, M5S 3G4, Canada
| | - Osman M Bakr
- Division of Physical Science and Engineering (PSE), King Abdullah University of Science and Technology (KAUST), Thuwal, Jeddah, 23955, Saudi Arabia
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16
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Schlosser A, Meyer LC, Lübkemann F, Miethe JF, Bigall NC. Nanoplatelet cryoaerogels with potential application in photoelectrochemical sensing. Phys Chem Chem Phys 2019; 21:9002-9012. [PMID: 30839040 PMCID: PMC6509881 DOI: 10.1039/c9cp00281b] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2019] [Accepted: 02/14/2019] [Indexed: 11/21/2022]
Abstract
Semiconductor nanoparticle based porous 3D assemblies are interesting materials for various applications in the fields of photovoltaics, catalysis, or optical sensing. For use as photoelectrodes in photoelectrochemical sensors they need to be characterised by a high porosity, a good photostability, and a high charge carrier mobility. Our work reports on the preparation of cryoaerogel photoelectrodes based on CdSe nanoplatelets and their photoelectrochemical characterisation by means of linear sweep voltammetry (LSV) and intensity modulated photocurrent spectroscopy (IMPS). The obtained open-pored cryoaerogel films were observed to produce much higher photocurrents than comparable drop-cast films. By means of IMPS, the performance differences could be linked to the occurrence of charge carrier movement, which could solely be proven for the cryoaerogels. In a proof-of-principle experiment, the potential of the prepared photoelectrodes for application in photoelectrochemical sensing was moreover demonstrated.
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Affiliation(s)
- Anja Schlosser
- Institute of Physical Chemistry and Electrochemistry
, Leibniz Universität Hannover
,
Callinstr. 3A
, 30167 Hannover
, Germany
.
; Fax: +49 511 762 19121
; Tel: +49 511 762 3185
- Laboratory of Nano and Quantum Engineering (LNQE)
, Leibniz Universität Hannover
,
Schneiderberg 39
, 30167 Hannover
, Germany
| | - Lea C. Meyer
- Institute of Physical Chemistry and Electrochemistry
, Leibniz Universität Hannover
,
Callinstr. 3A
, 30167 Hannover
, Germany
.
; Fax: +49 511 762 19121
; Tel: +49 511 762 3185
- Laboratory of Nano and Quantum Engineering (LNQE)
, Leibniz Universität Hannover
,
Schneiderberg 39
, 30167 Hannover
, Germany
| | - Franziska Lübkemann
- Institute of Physical Chemistry and Electrochemistry
, Leibniz Universität Hannover
,
Callinstr. 3A
, 30167 Hannover
, Germany
.
; Fax: +49 511 762 19121
; Tel: +49 511 762 3185
- Laboratory of Nano and Quantum Engineering (LNQE)
, Leibniz Universität Hannover
,
Schneiderberg 39
, 30167 Hannover
, Germany
| | - Jan F. Miethe
- Institute of Physical Chemistry and Electrochemistry
, Leibniz Universität Hannover
,
Callinstr. 3A
, 30167 Hannover
, Germany
.
; Fax: +49 511 762 19121
; Tel: +49 511 762 3185
- Laboratory of Nano and Quantum Engineering (LNQE)
, Leibniz Universität Hannover
,
Schneiderberg 39
, 30167 Hannover
, Germany
| | - Nadja C. Bigall
- Institute of Physical Chemistry and Electrochemistry
, Leibniz Universität Hannover
,
Callinstr. 3A
, 30167 Hannover
, Germany
.
; Fax: +49 511 762 19121
; Tel: +49 511 762 3185
- Laboratory of Nano and Quantum Engineering (LNQE)
, Leibniz Universität Hannover
,
Schneiderberg 39
, 30167 Hannover
, Germany
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17
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Proppe AH, Xu J, Sabatini RP, Fan JZ, Sun B, Hoogland S, Kelley SO, Voznyy O, Sargent EH. Picosecond Charge Transfer and Long Carrier Diffusion Lengths in Colloidal Quantum Dot Solids. NANO LETTERS 2018; 18:7052-7059. [PMID: 30359524 DOI: 10.1021/acs.nanolett.8b03020] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Quantum dots (QDs) are promising candidates for solution-processed thin-film optoelectronic devices. Both the diffusion length and the mobility of photoexcited charge carriers in QD solids are critical determinants of solar cell performance; yet various techniques offer diverse values of these key parameters even in notionally similar films. Here we report diffusion lengths and interdot charge transfer rates using a 3D donor/acceptor technique that directly monitors the rate at which photoexcitations reach small-bandgap dot inclusions having a known spacing within a larger-bandgap QD matrix. Instead of relying on photoluminescence (which can be weak in strongly coupled QD solids), we use ultrafast transient absorption spectroscopy, a method where sensitivity is undiminished by exciton dissociation. We measure record diffusion lengths of ∼300 nm in metal halide exchanged PbS QD solids that have led to power conversion efficiencies of 12%, and determine 8 ps interdot hopping of carriers following photoexcitation, among the fastest rates reported for PbS QD solids. We also find that QD solids composed of smaller QDs ( d = ∼3.2 nm) exhibit 5 times faster interdot charge transfer rates and 10 times lower trap state densities compared to larger ( d = ∼5.5 nm) QDs.
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Affiliation(s)
- Andrew H Proppe
- Department of Chemistry , University of Toronto , 80 St. George Street , Toronto , Ontario Canada , M5S 3G4
- The Edward S. Rogers Department of Electrical and Computer Engineering , University of Toronto , 10 King's College Road , Toronto , Ontario Canada , M5S 3G4
| | - Jixian Xu
- The Edward S. Rogers Department of Electrical and Computer Engineering , University of Toronto , 10 King's College Road , Toronto , Ontario Canada , M5S 3G4
| | - Randy P Sabatini
- The Edward S. Rogers Department of Electrical and Computer Engineering , University of Toronto , 10 King's College Road , Toronto , Ontario Canada , M5S 3G4
| | - James Z Fan
- The Edward S. Rogers Department of Electrical and Computer Engineering , University of Toronto , 10 King's College Road , Toronto , Ontario Canada , M5S 3G4
| | - Bin Sun
- The Edward S. Rogers Department of Electrical and Computer Engineering , University of Toronto , 10 King's College Road , Toronto , Ontario Canada , M5S 3G4
| | - Sjoerd Hoogland
- The Edward S. Rogers Department of Electrical and Computer Engineering , University of Toronto , 10 King's College Road , Toronto , Ontario Canada , M5S 3G4
| | - Shana O Kelley
- Department of Chemistry , University of Toronto , 80 St. George Street , Toronto , Ontario Canada , M5S 3G4
- Department of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy , University of Toronto, Toronto , Ontario Canada , M5S 3M2
| | - Oleksandr Voznyy
- The Edward S. Rogers Department of Electrical and Computer Engineering , University of Toronto , 10 King's College Road , Toronto , Ontario Canada , M5S 3G4
| | - Edward H Sargent
- The Edward S. Rogers Department of Electrical and Computer Engineering , University of Toronto , 10 King's College Road , Toronto , Ontario Canada , M5S 3G4
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18
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Photon antibunching in a cluster of giant CdSe/CdS nanocrystals. Nat Commun 2018; 9:1536. [PMID: 29670113 PMCID: PMC5906464 DOI: 10.1038/s41467-018-03971-w] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2017] [Accepted: 03/24/2018] [Indexed: 01/12/2023] Open
Abstract
When closely packed into a high-density film, semiconductor nanocrystals (NCs) can interact with each other to yield collective optical behaviours, which are normally difficult to characterize due to the ensemble average effect. Here we synthesized semiconductor NC clusters and performed single-particle spectroscopic measurements to probe the electronic couplings of several giant CdSe/CdS NCs contained in one cluster with nanometer-scale separations. Such a single cluster exhibits multiple emission peaks at the cryogenic temperature with nearly identical photoluminescence decay dynamics, suggesting that the Förster-type energy transfer does not occur among the composing NCs. Surprisingly, strong photon antibunching is still observed from a single cluster, which can be attributed to the Auger annihilation of photo-excited excitons from different NCs. The isolation of several nearby NCs interacting with the above novel mechanism has marked a solid progress towards a full understanding and an efficient control of the operation parameters in NC-based optoelectronic devices.
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19
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Yuan H, Debroye E, Bladt E, Lu G, Keshavarz M, Janssen KPF, Roeffaers MBJ, Bals S, Sargent EH, Hofkens J. Imaging Heterogeneously Distributed Photo-Active Traps in Perovskite Single Crystals. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2018; 30:e1705494. [PMID: 29457290 DOI: 10.1002/adma.201705494] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/22/2017] [Revised: 01/04/2018] [Indexed: 05/25/2023]
Abstract
Organic-inorganic halide perovskites (OIHPs) have demonstrated outstanding energy conversion efficiency in solar cells and light-emitting devices. In spite of intensive developments in both materials and devices, electronic traps and defects that significantly affect their device properties remain under-investigated. Particularly, it remains challenging to identify and to resolve traps individually at the nanoscopic scale. Here, photo-active traps (PATs) are mapped over OIHP nanocrystal morphology of different crystallinity by means of correlative optical differential super-resolution localization microscopy (Δ-SRLM) and electron microscopy. Stochastic and monolithic photoluminescence intermittency due to individual PATs is observed on monocrystalline and polycrystalline OIHP nanocrystals. Δ-SRLM reveals a heterogeneous PAT distribution across nanocrystals and determines the PAT density to be 1.3 × 1014 and 8 × 1013 cm-3 for polycrystalline and for monocrystalline nanocrystals, respectively. The higher PAT density in polycrystalline nanocrystals is likely related to an increased defect density. Moreover, monocrystalline nanocrystals that are prepared in an oxygen- and moisture-free environment show a similar PAT density as that prepared at ambient conditions, excluding oxygen or moisture as chief causes of PATs. Hence, it is concluded that the PATs come from inherent structural defects in the material, which suggests that the PAT density can be reduced by improving crystalline quality of the material.
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Affiliation(s)
- Haifeng Yuan
- Department of Chemistry, KU Leuven, Celestijnenlaan 200F, B-3001, Leuven, Belgium
- Department of Electrical and Computer Engineering, University of Toronto, 10 King's College Road, Toronto, Ontario, M5S 3G4, Canada
| | - Elke Debroye
- Department of Chemistry, KU Leuven, Celestijnenlaan 200F, B-3001, Leuven, Belgium
| | - Eva Bladt
- EMAT, University of Antwerp, Groenenborgerlaan 171, 2020, Antwerp, Belgium
| | - Gang Lu
- Department of Chemistry, KU Leuven, Celestijnenlaan 200F, B-3001, Leuven, Belgium
- Key Laboratory of Flexible Electronics & Institute of Advanced Materials, Nanjing Tech University, 30 South Puzhu Road, 211816, Nanjing, China
| | - Masoumeh Keshavarz
- Department of Chemistry, KU Leuven, Celestijnenlaan 200F, B-3001, Leuven, Belgium
| | - Kris P F Janssen
- Department of Chemistry, KU Leuven, Celestijnenlaan 200F, B-3001, Leuven, Belgium
| | - Maarten B J Roeffaers
- Centre for Surface Chemistry and Catalysis, KU Leuven, Celestijnenlaan 200F, B-3001, Leuven, Belgium
| | - Sara Bals
- EMAT, University of Antwerp, Groenenborgerlaan 171, 2020, Antwerp, Belgium
| | - Edward H Sargent
- Department of Electrical and Computer Engineering, University of Toronto, 10 King's College Road, Toronto, Ontario, M5S 3G4, Canada
| | - Johan Hofkens
- Department of Chemistry, KU Leuven, Celestijnenlaan 200F, B-3001, Leuven, Belgium
- RIES, Hokkaido University, N20W10, Kita-Ward Sapporo, 001-0020, Japan
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20
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Zhang X, Cheng H, Zhang H. Recent Progress in the Preparation, Assembly, Transformation, and Applications of Layer-Structured Nanodisks beyond Graphene. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2017; 29:1701704. [PMID: 28715123 DOI: 10.1002/adma.201701704] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2017] [Revised: 05/14/2017] [Indexed: 06/07/2023]
Abstract
Layered nanodisks with confined thickness and lateral size have been emerging as a unique type of two-dimensional (2D) nanomaterials in recent years. Inheriting some properties of 2D nanosheets and meanwhile possessing the size-confinement effect, these layered nanodisks exhibit unique optical, electronic, and chemical properties, which endow them with great promise in a wide range of applications. Here, the recent progress of layered nanodisks is introduced. The synthetic strategies, assembly, structural/compositional transformation, and applications of layered nanodisks are systematically described and discussed, with emphasis on their new appealing structures and functions. Finally, some perspectives and future research directions of this promising field are given.
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Affiliation(s)
- Xiao Zhang
- Center for Programmable Materials, School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore, 639798, Singapore
| | - Hongfei Cheng
- Center for Programmable Materials, School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore, 639798, Singapore
| | - Hua Zhang
- Center for Programmable Materials, School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore, 639798, Singapore
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21
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Kaniyankandy S, Verma S. Role of Core-Shell Formation in Exciton Confinement Relaxation in Dithiocarbamate-Capped CdSe QDs. J Phys Chem Lett 2017; 8:3228-3233. [PMID: 28661145 DOI: 10.1021/acs.jpclett.7b01259] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The possibility of exciton delocalization in alkyldithiocarbamate (ATC)-capped CdSe has been investigated for several alkyl groups and compared with phenyldithiocarbamates (PTCs). We find a bathochromic shift for ATC similar to the one obtained for PTC. Our computational studies show reduction in HOMO-LUMO gaps in both PTC and ATC, albeit with a lower shift. However, TDDFT studies revealed that ATC-capped CdSe is more of a localized HOMO state as compared with partly delocalized HOMO in PTC-capped CdSe, hinting at a difference in electronic interaction between the two binding groups. We hypothesized the formation of sulfide layer over the CdSe QDs as the possible reason for the observed bathochromic shift, as verified by absorption spectra of S2- ligand exchange samples. The formation of CdS shell leads to substantial electron delocalization because CdSe CB is in close resonance with CdS, which is exactly the opposite of what was previously concluded in the literature.
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Affiliation(s)
- Sreejith Kaniyankandy
- Radiation & Photochemistry Division, Bhabha Atomic Research Centre , Trombay, Mumbai 400085, India
| | - Sandeep Verma
- Radiation & Photochemistry Division, Bhabha Atomic Research Centre , Trombay, Mumbai 400085, India
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22
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Nguyen D, Nguyen HA, Lyding JW, Gruebele M. Imaging and Manipulating Energy Transfer Among Quantum Dots at Individual Dot Resolution. ACS NANO 2017; 11:6328-6335. [PMID: 28525955 DOI: 10.1021/acsnano.7b02649] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Many processes of interest in quantum dots involve charge or energy transfer from one dot to another. Energy transfer in films of quantum dots as well as between linked quantum dots has been demonstrated by luminescence shift, and the ultrafast time-dependence of energy transfer processes has been resolved. Bandgap variation among dots (energy disorder) and dot separation are known to play an important role in how energy diffuses. Thus, it would be very useful if energy transfer could be visualized directly on a dot-by-dot basis among small clusters or within films of quantum dots. To that effect, we report single molecule optical absorption detected by scanning tunneling microscopy (SMA-STM) to image energy pooling from donor into acceptor dots on a dot-by-dot basis. We show that we can manipulate groups of quantum dots by pruning away the dominant acceptor dot, and switching the energy transfer path to a different acceptor dot. Our experimental data agrees well with a simple Monte Carlo lattice model of energy transfer, similar to models in the literature, in which excitation energy is transferred preferentially from dots with a larger bandgap to dots with a smaller bandgap.
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Affiliation(s)
| | | | | | - Martin Gruebele
- Department of Physics, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States
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23
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Sher PH, Wang JK. Interrogating surface state of isolated and agglomerated PbS quantum dots with solvent-induced stress. NANOTECHNOLOGY 2017; 28:165703. [PMID: 28230538 DOI: 10.1088/1361-6528/aa6286] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Applications of quantum dots (QDs) are often obstructed by the associated surface electronic states that quench photoluminescence (PL) and hinder charge transport. Preventing this is still largely being stymied owing to the lack of means to regulate their presence. Dispersing PbS QDs in toluene, we show that varying the solvent temperature offers a way of modulating their surface electronic state. A comprehensive energy-transfer model explains all the anomalous temperature-dependent behavior of the absorption and PL, explicitly revealing the PL quenching dynamics of isolated QDs due to the induced surface state by imposing solvent stress on their surface ligands. This study demonstrates that the local stress induced by a solvent can serve as a 'switch' for the surface electronic states of QDs, which is enabled by the well-studied thermo-physical properties of a liquid solvent.
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Affiliation(s)
- Pin-Hao Sher
- Institute of Atomic and Molecular Sciences, Academia Sinica, PO Box 23-166, Taipei 10617, Taiwan
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24
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Slow cooling and highly efficient extraction of hot carriers in colloidal perovskite nanocrystals. Nat Commun 2017; 8:14350. [PMID: 28176882 PMCID: PMC5309769 DOI: 10.1038/ncomms14350] [Citation(s) in RCA: 148] [Impact Index Per Article: 21.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2016] [Accepted: 12/20/2016] [Indexed: 12/23/2022] Open
Abstract
Hot-carrier solar cells can overcome the Shockley-Queisser limit by harvesting excess energy from hot carriers. Inorganic semiconductor nanocrystals are considered prime candidates. However, hot-carrier harvesting is compromised by competitive relaxation pathways (for example, intraband Auger process and defects) that overwhelm their phonon bottlenecks. Here we show colloidal halide perovskite nanocrystals transcend these limitations and exhibit around two orders slower hot-carrier cooling times and around four times larger hot-carrier temperatures than their bulk-film counterparts. Under low pump excitation, hot-carrier cooling mediated by a phonon bottleneck is surprisingly slower in smaller nanocrystals (contrasting with conventional nanocrystals). At high pump fluence, Auger heating dominates hot-carrier cooling, which is slower in larger nanocrystals (hitherto unobserved in conventional nanocrystals). Importantly, we demonstrate efficient room temperature hot-electrons extraction (up to ∼83%) by an energy-selective electron acceptor layer within 1 ps from surface-treated perovskite NCs thin films. These insights enable fresh approaches for extremely thin absorber and concentrator-type hot-carrier solar cells. Harvesting excess energy from above-band gap photons could lead to solar cells which exceed conventional efficiency limits. Li et al., study hot carrier cooling in hybrid perovskite materials with reduced dimensionality using transient absorption spectroscopy and demonstrate efficient hot-electron extraction in such systems.
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25
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Reich KV, Shklovskii BI. Exciton Transfer in Array of Epitaxially Connected Nanocrystals. ACS NANO 2016; 10:10267-10274. [PMID: 27805356 DOI: 10.1021/acsnano.6b05846] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Recently, epitaxially connected at facets semiconductor nanocrystals (NCs) have been introduced to fascilitate the electron transport between nanocrystals. To fully deploy their potential, a better understanding of the exciton transfer between connected NCs is needed. We go beyond the two well-known transfer mechanisms suggested by Förster and Dexter and propose a third mechanism of exciton tandem tunneling. The tandem tunneling occurs through the intermediate state in which the electron and hole are in different NCs. The corresponding rate for exciton hops is larger than the Dexter rate and for Si is even much larger that the Förster one.
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Affiliation(s)
- Konstantin V Reich
- Fine Theoretical Physics Institute, University of Minnesota , Minneapolis, Minnesota 55455, United States
- Ioffe Institute , St. Petersburg, 194021, Russia
| | - Boris I Shklovskii
- Fine Theoretical Physics Institute, University of Minnesota , Minneapolis, Minnesota 55455, United States
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26
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Walravens W, De Roo J, Drijvers E, Ten Brinck S, Solano E, Dendooven J, Detavernier C, Infante I, Hens Z. Chemically Triggered Formation of Two-Dimensional Epitaxial Quantum Dot Superlattices. ACS NANO 2016; 10:6861-6870. [PMID: 27383262 DOI: 10.1021/acsnano.6b02562] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Two dimensional superlattices of epitaxially connected quantum dots enable size-quantization effects to be combined with high charge carrier mobilities, an essential prerequisite for highly performing QD devices based on charge transport. Here, we demonstrate that surface active additives known to restore nanocrystal stoichiometry can trigger the formation of epitaxial superlattices of PbSe and PbS quantum dots. More specifically, we show that both chalcogen-adding (sodium sulfide) and lead oleate displacing (amines) additives induce small area epitaxial superlattices of PbSe quantum dots. In the latter case, the amine basicity is a sensitive handle to tune the superlattice symmetry, with strong and weak bases yielding pseudohexagonal or quasi-square lattices, respectively. Through density functional theory calculations and in situ titrations monitored by nuclear magnetic resonance spectroscopy, we link this observation to the concomitantly different coordination enthalpy and ligand displacement potency of the amine. Next to that, an initial ∼10% reduction of the initial ligand density prior to monolayer formation and addition of a mild, lead oleate displacing chemical trigger such as aniline proved key to induce square superlattices with long-range, square micrometer order; an effect that is the more pronounced the larger the quantum dots. Because the approach applies to PbS quantum dots as well, we conclude that it offers a reproducible and rational method for the formation of highly ordered epitaxial quantum dot superlattices.
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Affiliation(s)
| | | | | | - Stephanie Ten Brinck
- Department of Theoretical Chemistry, Vrije Universiteit Amsterdam , 1081 HV Amsterdam, The Netherlands
| | | | | | | | - Ivan Infante
- Department of Theoretical Chemistry, Vrije Universiteit Amsterdam , 1081 HV Amsterdam, The Netherlands
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27
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Cummins DR, Martinez U, Sherehiy A, Kappera R, Martinez-Garcia A, Schulze RK, Jasinski J, Zhang J, Gupta RK, Lou J, Chhowalla M, Sumanasekera G, Mohite AD, Sunkara MK, Gupta G. Efficient hydrogen evolution in transition metal dichalcogenides via a simple one-step hydrazine reaction. Nat Commun 2016; 7:11857. [PMID: 27282871 PMCID: PMC4906413 DOI: 10.1038/ncomms11857] [Citation(s) in RCA: 82] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2015] [Accepted: 05/06/2016] [Indexed: 12/24/2022] Open
Abstract
Hydrogen evolution reaction is catalysed efficiently with precious metals, such as platinum; however, transition metal dichalcogenides have recently emerged as a promising class of materials for electrocatalysis, but these materials still have low activity and durability when compared with precious metals. Here we report a simple one-step scalable approach, where MoOx/MoS2 core-shell nanowires and molybdenum disulfide sheets are exposed to dilute aqueous hydrazine at room temperature, which results in marked improvement in electrocatalytic performance. The nanowires exhibit ∼100 mV improvement in overpotential following exposure to dilute hydrazine, while also showing a 10-fold increase in current density and a significant change in Tafel slope. In situ electrical, gate-dependent measurements and spectroscopic investigations reveal that hydrazine acts as an electron dopant in molybdenum disulfide, increasing its conductivity, while also reducing the MoOx core in the core-shell nanowires, which leads to improved electrocatalytic performance. Transition metal dichalcogenides are promising hydrogen evolution catalysts however they can require expensive processing steps to enhance their activity. Here, the authors report a one-step activation step in which room temperature hydrazine treatment results in much enhanced electrocatalytic performance.
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Affiliation(s)
- Dustin R Cummins
- Materials Physics and Applications (MPA-11), Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.,Chemical Engineering and Conn Center for Renewable Energy Research, University of Louisville, Louisville, Kentucky 40292, USA
| | - Ulises Martinez
- Materials Physics and Applications (MPA-11), Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - Andriy Sherehiy
- Chemical Engineering and Conn Center for Renewable Energy Research, University of Louisville, Louisville, Kentucky 40292, USA
| | - Rajesh Kappera
- Materials Physics and Applications (MPA-11), Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.,Materials Science and Engineering, Rutgers University, Piscataway, New Jersey 08854, USA
| | - Alejandro Martinez-Garcia
- Chemical Engineering and Conn Center for Renewable Energy Research, University of Louisville, Louisville, Kentucky 40292, USA
| | - Roland K Schulze
- Materials Science and Technology (MST-6), Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - Jacek Jasinski
- Chemical Engineering and Conn Center for Renewable Energy Research, University of Louisville, Louisville, Kentucky 40292, USA
| | - Jing Zhang
- Materials Science and NanoEngineering, Rice University, Houston, Texas 77005, USA
| | - Ram K Gupta
- Chemistry, Pittsburg State University, Pittsburg, Kansas 66762, USA
| | - Jun Lou
- Materials Science and NanoEngineering, Rice University, Houston, Texas 77005, USA
| | - Manish Chhowalla
- Materials Science and Engineering, Rutgers University, Piscataway, New Jersey 08854, USA
| | - Gamini Sumanasekera
- Chemical Engineering and Conn Center for Renewable Energy Research, University of Louisville, Louisville, Kentucky 40292, USA
| | - Aditya D Mohite
- Materials Physics and Applications (MPA-11), Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - Mahendra K Sunkara
- Chemical Engineering and Conn Center for Renewable Energy Research, University of Louisville, Louisville, Kentucky 40292, USA
| | - Gautam Gupta
- Materials Physics and Applications (MPA-11), Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
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28
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Kim BS, Neo DJ, Hou B, Park JB, Cho Y, Zhang N, Hong J, Pak S, Lee S, Sohn JI, Assender HE, Watt AAR, Cha S, Kim J. High Performance PbS Quantum Dot/Graphene Hybrid Solar Cell with Efficient Charge Extraction. ACS APPLIED MATERIALS & INTERFACES 2016; 8:13902-8. [PMID: 27213219 PMCID: PMC4928821 DOI: 10.1021/acsami.6b02544] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/29/2016] [Accepted: 05/13/2016] [Indexed: 05/19/2023]
Abstract
Hybrid colloidal quantum dot (CQD) solar cells are fabricated from multilayer stacks of lead sulfide (PbS) CQD and single layer graphene (SG). The inclusion of graphene interlayers is shown to increase power conversion efficiency by 9.18%. It is shown that the inclusion of conductive graphene enhances charge extraction in devices. Photoluminescence shows that graphene quenches emission from the quantum dot suggesting spontaneous charge transfer to graphene. CQD photodetectors exhibit increased photoresponse and improved transport properties. We propose that the CQD/SG hybrid structure is a route to make CQD thin films with improved charge extraction, therefore resulting in improved solar cell efficiency.
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Affiliation(s)
- Byung-Sung Kim
- Department
of Engineering Science, University of Oxford, Parks Road, Oxford OX1 3PJ, U.K.
| | - Darren
C. J. Neo
- Department
of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, U.K.
| | - Bo Hou
- Department
of Engineering Science, University of Oxford, Parks Road, Oxford OX1 3PJ, U.K.
| | - Jong Bae Park
- Department
of Engineering Science, University of Oxford, Parks Road, Oxford OX1 3PJ, U.K.
- Jeonju
Centre, Korea Basic Science Institute, Jeonju, Jeollabuk-do 561-180, Republic of Korea
| | - Yuljae Cho
- Department
of Engineering Science, University of Oxford, Parks Road, Oxford OX1 3PJ, U.K.
| | - Nanlin Zhang
- Department
of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, U.K.
| | - John Hong
- Department
of Engineering Science, University of Oxford, Parks Road, Oxford OX1 3PJ, U.K.
| | - Sangyeon Pak
- Department
of Engineering Science, University of Oxford, Parks Road, Oxford OX1 3PJ, U.K.
| | - Sanghyo Lee
- Department
of Engineering Science, University of Oxford, Parks Road, Oxford OX1 3PJ, U.K.
| | - Jung Inn Sohn
- Department
of Engineering Science, University of Oxford, Parks Road, Oxford OX1 3PJ, U.K.
| | - Hazel E. Assender
- Department
of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, U.K.
| | - Andrew A. R. Watt
- Department
of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, U.K.
- E-mail:
| | - SeungNam Cha
- Department
of Engineering Science, University of Oxford, Parks Road, Oxford OX1 3PJ, U.K.
- E-mail:
| | - Jong
Min Kim
- Department
of Engineering, University of Cambridge, 9 JJ Thomson Avenue, Cambridge CB3 0FA, U.K.
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29
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Lukose B, Clancy P. A feasibility study of unconventional planar ligand spacers in chalcogenide nanocrystals. Phys Chem Chem Phys 2016; 18:13781-93. [PMID: 26918246 DOI: 10.1039/c5cp07521a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The solar cell efficiency of chalcogenide nanocrystals (quantum dots) has been limited in the past by the insulation between neighboring quantum dots caused by intervening, often long-chain, aliphatic ligands. We have conducted a computationally based feasibility study to investigate the use of ultra-thin, planar, charge-conducting ligands as an alternative to traditional long passive ligands. Not only might these radically unconventional ligands decrease the mean distance between adjacent quantum dots, but, since they are charge-conducting, they have the potential to actively enhance charge migration. Our ab initio studies compare the binding energies, electronic energy gaps, and absorption characteristics for both conventional and unconventional ligands, such as phthalocyanines, porphyrins and coronene. This comparison identified these unconventional ligands with the exception of titanyl phthalocyanine, that bind to themselves more strongly than to the surface of the quantum dot, which is likely to be less desirable for enhancing charge transport. The distribution of finite energy levels of the bound system is sensitive to the ligand's binding site and the levels correspond to delocalized states. We also observed a trap state localized on a single Pb atom when a sulfur-containing phenyldithiocarbamate (PTC) ligand is attached to a slightly off-stoichiometric dot in a manner that the sulfur of the ligand completes stoichiometry of the bound system. Hence, this is indicative of the source of trap state when thio-based ligands are bound to chalcogenide nanocrystals. We also predict that titanyl phthalocyanine in a mix with chalcogenide dots of diameter ∼1.5 Å can form a donor-acceptor system.
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Affiliation(s)
- Binit Lukose
- School of Chemical and Biomolecular Engineering, Cornell University, 14853 Ithaca, NY, USA.
| | - Paulette Clancy
- School of Chemical and Biomolecular Engineering, Cornell University, 14853 Ithaca, NY, USA.
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30
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Mahadevu R, Kaur H, Pandey A. Hidden role of anion exchange reactions in nucleation of colloidal nanocrystals. CrystEngComm 2016. [DOI: 10.1039/c5ce02114f] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
We show the existence and importance of anion exchange reactions in colloidal chemistry.
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Affiliation(s)
- Rekha Mahadevu
- Solid State and Structural Chemistry Unit
- Indian Institute of Science
- Bangalore 560012, India
| | - Harveen Kaur
- Solid State and Structural Chemistry Unit
- Indian Institute of Science
- Bangalore 560012, India
| | - Anshu Pandey
- Solid State and Structural Chemistry Unit
- Indian Institute of Science
- Bangalore 560012, India
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31
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Yang Z, Yassitepe E, Voznyy O, Janmohamed A, Lan X, Levina L, Comin R, Sargent EH. Self-Assembled PbSe Nanowire:Perovskite Hybrids. J Am Chem Soc 2015; 137:14869-72. [PMID: 26565433 DOI: 10.1021/jacs.5b10641] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Inorganic semiconductor nanowires are of interest in nano- and microscale photonic and electronic applications. Here we report the formation of PbSe nanowires based on directional quantum dot alignment and fusion regulated by hybrid organic-inorganic perovskite surface ligands. All material synthesis is carried out at mild temperatures. Passivation of PbSe quantum dots was achieved via a new perovskite ligand exchange. Subsequent in situ ammonium/amine substitution by butylamine enables quantum dots to be capped by butylammonium lead iodide, and this further drives the formation of a PbSe nanowire superlattice in a two-dimensional (2D) perovskite matrix. The average spacing between two adjacent nanowires agrees well with the thickness of single atomic layer of 2D perovskite, consistent with the formation of a new self-assembled semiconductor nanowire:perovskite heterocrystal hybrid.
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Affiliation(s)
- Zhenyu Yang
- The Edward S. Rogers Department of Electrical and Computer Engineering, University of Toronto , 10 King's College Road, Toronto, Ontario M5S 3G4, Canada
| | - Emre Yassitepe
- The Edward S. Rogers Department of Electrical and Computer Engineering, University of Toronto , 10 King's College Road, Toronto, Ontario M5S 3G4, Canada
| | - Oleksandr Voznyy
- The Edward S. Rogers Department of Electrical and Computer Engineering, University of Toronto , 10 King's College Road, Toronto, Ontario M5S 3G4, Canada
| | - Alyf Janmohamed
- The Edward S. Rogers Department of Electrical and Computer Engineering, University of Toronto , 10 King's College Road, Toronto, Ontario M5S 3G4, Canada
| | - Xinzheng Lan
- The Edward S. Rogers Department of Electrical and Computer Engineering, University of Toronto , 10 King's College Road, Toronto, Ontario M5S 3G4, Canada
| | - Larissa Levina
- The Edward S. Rogers Department of Electrical and Computer Engineering, University of Toronto , 10 King's College Road, Toronto, Ontario M5S 3G4, Canada
| | - Riccardo Comin
- The Edward S. Rogers Department of Electrical and Computer Engineering, University of Toronto , 10 King's College Road, Toronto, Ontario M5S 3G4, Canada
| | - Edward H Sargent
- The Edward S. Rogers Department of Electrical and Computer Engineering, University of Toronto , 10 King's College Road, Toronto, Ontario M5S 3G4, Canada
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32
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Whitcomb KJ, Geisenhoff JQ, Ryan DP, Gelfand MP, Van Orden A. Photon Antibunching in Small Clusters of CdSe/ZnS Core/Shell Quantum Dots. J Phys Chem B 2015; 119:9020-8. [PMID: 25232642 DOI: 10.1021/jp5083856] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Coincident photon histogram measurements of fluorescence antibunching via confocal microscopy correlated with atomic force microscopy were carried out on (i) individual CdSe/ZnS core/shell quantum dots (QDs), (ii) several well separated QDs, and (iii) clusters of QDs. Individual QDs and well separated QDs showed the expected degree of antibunching for a single emitter and several independent emitters, respectively. The degree of antibunching in small, compact clusters was more characteristic of a single emitter than multiple emitters. The antibunching in clusters provides strong evidence of nonradiative energy transfer between QDs in a cluster. A minimal phenomenological model of energy transfer gives reasonable quantitative agreement with the experimental results.
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Affiliation(s)
- Kevin J Whitcomb
- †Department of Chemistry and ‡Department of Physics, Colorado State University, Fort Collins, Colorado 80523, United States
| | - Jessica Q Geisenhoff
- †Department of Chemistry and ‡Department of Physics, Colorado State University, Fort Collins, Colorado 80523, United States
| | - Duncan P Ryan
- †Department of Chemistry and ‡Department of Physics, Colorado State University, Fort Collins, Colorado 80523, United States
| | - Martin P Gelfand
- †Department of Chemistry and ‡Department of Physics, Colorado State University, Fort Collins, Colorado 80523, United States
| | - Alan Van Orden
- †Department of Chemistry and ‡Department of Physics, Colorado State University, Fort Collins, Colorado 80523, United States
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33
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Lawrence KN, Johnson MA, Dolai S, Kumbhar A, Sardar R. Solvent-like ligand-coated ultrasmall cadmium selenide nanocrystals: strong electronic coupling in a self-organized assembly. NANOSCALE 2015; 7:11667-11677. [PMID: 26098759 DOI: 10.1039/c5nr02038g] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Strong inter-nanocrystal electronic coupling is a prerequisite for delocalization of exciton wave functions and high conductivity. We report 170 meV electronic coupling energy of short chain poly(ethylene glycol) thiolate-coated ultrasmall (<2.5 nm in diameter) CdSe semiconductor nanocrystals (SNCs) in solution. Cryo-transmission electron microscopy analysis showed the formation of a pearl-necklace assembly of nanocrystals in solution with regular inter-nanocrystal spacing. The electronic coupling was studied as a function of CdSe nanocrystal size where the smallest nanocrystals exhibited the largest coupling energy. The electronic coupling in spin-cast thin-film (<200 nm in thickness) of poly(ethylene glycol) thiolate-coated CdSe SNCs was studied as a function of annealing temperature, where an unprecedentedly large, ∼400 meV coupling energy was observed for 1.6 nm diameter SNCs, which were coated with a thin layer of poly(ethylene glycol) thiolates. Small-angle X-ray scattering measurements showed that CdSe SNCs maintained an order array inside the films. The strong electronic coupling of SNCs in a self-organized film could facilitate the large-scale production of highly efficient electronic materials for advanced optoelectronic device application.
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Affiliation(s)
- Katie N Lawrence
- Department of Chemistry and Chemical Biology, Indiana University-Purdue University Indianapolis, 402 N. Blackford Street, Indianapolis, Indiana 46202, USA.
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34
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Logar M, Xu S, Acharya S, Prinz FB. Variation of energy density of states in quantum dot arrays due to interparticle electronic coupling. NANO LETTERS 2015; 15:1855-1860. [PMID: 25670055 DOI: 10.1021/nl5046507] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Subnanometer-resolved local electron energy structure was measured in PbS quantum dot superlattice arrays using valence electron energy loss spectroscopy with scanning transmission electron microscopy. We found smaller values of the lowest available transition energies and an increased density of electronic states in the space between quantum dots with shorter interparticle spacing, indicating extension of carrier wave functions as a result of interparticle electronic coupling. A quantum simulation verified both trends and illustrated the wave function extension effect.
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Affiliation(s)
- Manca Logar
- Department of Mechanical Engineering and ‡Department of Material Science and Engineering, Stanford University , Stanford, California 94305, United States
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35
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Guglietta GW, Diroll BT, Gaulding EA, Fordham JL, Li S, Murray CB, Baxter JB. Lifetime, mobility, and diffusion of photoexcited carriers in ligand-exchanged lead selenide nanocrystal films measured by time-resolved terahertz spectroscopy. ACS NANO 2015; 9:1820-8. [PMID: 25644854 DOI: 10.1021/nn506724h] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Colloidal semiconductor nanocrystals have been used as building blocks for electronic and optoelectronic devices ranging from field-effect transistors to solar cells. Properties of the nanocrystal films depend sensitively on the choice of capping ligand to replace the insulating synthesis ligands. Thus far, ligands leading to the best performance in transistors result in poor solar cell performance, and vice versa. To gain insight into the nature of this dichotomy, we used time-resolved terahertz spectroscopy measurements to study the mobility and lifetime of PbSe nanocrystal films prepared with five common ligand-exchange reagents. Noncontact terahertz spectroscopy measurements of conductivity were corroborated by contacted van der Pauw measurements of the same samples. The films treated with different displacing ligands show more than an order of magnitude difference in the peak conductivities and a bifurcation of time dynamics. Inorganic chalcogenide ligand exchanges with sodium sulfide (Na2S) or ammonium thiocyanate (NH4SCN) show high mobilities but nearly complete decay of transient photocurrent in 1.4 ns. In contrast, ligand exchanges with 1,2-ethylenediamine (EDA), 1,2-ethanedithiol (EDT), and tetrabutylammonium iodide (TBAI) show lower mobilities but longer carrier lifetimes, resulting in longer diffusion lengths. This bifurcated behavior may explain the divergent performance of field-effect transistors and photovoltaics constructed from nanocrystal building blocks with different ligand exchanges.
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Affiliation(s)
- Glenn W Guglietta
- Department of Chemical and Biological Engineering, Drexel University , 3141 Chestnut Street, Philadelphia, Pennsylvania 19104, United States
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36
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A quantitative model for charge carrier transport, trapping and recombination in nanocrystal-based solar cells. Nat Commun 2015; 6:6180. [PMID: 25625647 PMCID: PMC4317500 DOI: 10.1038/ncomms7180] [Citation(s) in RCA: 102] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2014] [Accepted: 12/27/2014] [Indexed: 12/23/2022] Open
Abstract
Improving devices incorporating solution-processed nanocrystal-based semiconductors requires a better understanding of charge transport in these complex, inorganic–organic materials. Here we perform a systematic study on PbS nanocrystal-based diodes using temperature-dependent current–voltage characterization and thermal admittance spectroscopy to develop a model for charge transport that is applicable to different nanocrystal-solids and device architectures. Our analysis confirms that charge transport occurs in states that derive from the quantum-confined electronic levels of the individual nanocrystals and is governed by diffusion-controlled trap-assisted recombination. The current is limited not by the Schottky effect, but by Fermi-level pinning because of trap states that is independent of the electrode–nanocrystal interface. Our model successfully explains the non-trivial trends in charge transport as a function of nanocrystal size and the origins of the trade-offs facing the optimization of nanocrystal-based solar cells. We use the insights from our charge transport model to formulate design guidelines for engineering higher-performance nanocrystal-based devices. Colloidal nanocrystals could help improve the performance of the next generation of solar cells, but a model that fully describes the electronic behaviour of such devices is missing. Bozyigit et al. now develop a quantitative model for charge transport in these solar cells.
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37
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Yakunin S, Dirin DN, Protesescu L, Sytnyk M, Tollabimazraehno S, Humer M, Hackl F, Fromherz T, Bodnarchuk MI, Kovalenko MV, Heiss W. High infrared photoconductivity in films of arsenic-sulfide-encapsulated lead-sulfide nanocrystals. ACS NANO 2014; 8:12883-94. [PMID: 25470412 PMCID: PMC4278417 DOI: 10.1021/nn5067478] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2014] [Accepted: 12/03/2014] [Indexed: 05/21/2023]
Abstract
Highly photoconductive thin films of inorganic-capped PbS nanocrystal quantum dots (QDs) are reported. Stable colloidal dispersions of (NH4)3AsS3-capped PbS QDs were processed by a conventional dip-coating technique into a thin homogeneous film of electronically coupled PbS QDs. Upon drying at 130 °C, (NH4)3AsS3 capping ligands were converted into a thin layer of As2S3, acting as an infrared-transparent semiconducting glue. Photodetectors obtained by depositing such films onto glass substrates with interdigitate electrode structures feature extremely high light responsivity and detectivity with values of more than 200 A/W and 1.2×10(13) Jones, respectively, at infrared wavelengths up to 1400 nm. Importantly, these devices were fabricated and tested under ambient atmosphere. Using a set of time-resolved optoelectronic experiments, the important role played by the carrier trap states, presumably localized on the arsenic-sulfide surface coating, has been elucidated. Foremost, these traps enable a very high photoconductive gain of at least 200. The trap state density as a function of energy has been plotted from the frequency dependence of the photoinduced absorption (PIA), whereas the distribution of lifetimes of these traps was recovered from PIA and photoconductivity (PC) phase spectra. These trap states also have an important impact on carrier dynamics, which led us to propose a kinetic model for trap state filling that consistently describes the experimental photoconductivity transients at various intensities of excitation light. This model also provides realistic values for the photoconductive gain and thus may serve as a useful tool to describe photoconductivity in nanocrystal-based solids.
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Affiliation(s)
- Sergii Yakunin
- Institute of Semiconductor and Solid State Physics, Johannes Kepler University Linz, Altenbergerstraße 69, Linz 4040, Austria
- Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 1, Zurich CH-8093, Switzerland
- Empa-Swiss Federal Laboratories for Materials Science and Technology, Überlandstraße 129, Dübendorf CH-8600, Switzerland
| | - Dmitry N. Dirin
- Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 1, Zurich CH-8093, Switzerland
- Empa-Swiss Federal Laboratories for Materials Science and Technology, Überlandstraße 129, Dübendorf CH-8600, Switzerland
| | - Loredana Protesescu
- Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 1, Zurich CH-8093, Switzerland
- Empa-Swiss Federal Laboratories for Materials Science and Technology, Überlandstraße 129, Dübendorf CH-8600, Switzerland
| | - Mykhailo Sytnyk
- Institute of Semiconductor and Solid State Physics, Johannes Kepler University Linz, Altenbergerstraße 69, Linz 4040, Austria
| | - Sajjad Tollabimazraehno
- Zentrum für Oberflächen- und Nanoanalytik, University Linz, Altenbergerstraße 69, Linz 4040, Austria
| | - Markus Humer
- Institute of Semiconductor and Solid State Physics, Johannes Kepler University Linz, Altenbergerstraße 69, Linz 4040, Austria
| | - Florian Hackl
- Institute of Semiconductor and Solid State Physics, Johannes Kepler University Linz, Altenbergerstraße 69, Linz 4040, Austria
| | - Thomas Fromherz
- Institute of Semiconductor and Solid State Physics, Johannes Kepler University Linz, Altenbergerstraße 69, Linz 4040, Austria
| | - Maryna I. Bodnarchuk
- Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 1, Zurich CH-8093, Switzerland
- Empa-Swiss Federal Laboratories for Materials Science and Technology, Überlandstraße 129, Dübendorf CH-8600, Switzerland
| | - Maksym V. Kovalenko
- Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 1, Zurich CH-8093, Switzerland
- Empa-Swiss Federal Laboratories for Materials Science and Technology, Überlandstraße 129, Dübendorf CH-8600, Switzerland
| | - Wolfgang Heiss
- Institute of Semiconductor and Solid State Physics, Johannes Kepler University Linz, Altenbergerstraße 69, Linz 4040, Austria
- Materials for Electronics and Energy Technology (i-MEET), Friedrich-Alexander-Universität Erlangen-Nürnberg, Martensstraße 7, 91058 Erlangen, Germany
- Energie Campus Nürnberg (EnCN), Fürther Straße 250, 90429 Nürnberg, Germany
- Address correspondence to
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38
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Fu W, Wang L, Zhang Y, Ma R, Zuo L, Mai J, Lau TK, Du S, Lu X, Shi M, Li H, Chen H. Improving polymer/nanocrystal hybrid solar cell performance via tuning ligand orientation at CdSe quantum dot surface. ACS APPLIED MATERIALS & INTERFACES 2014; 6:19154-19160. [PMID: 25336155 DOI: 10.1021/am505130a] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Achieving superior solar cell performance based on the colloidal nanocrystals remains challenging due to their complex surface composition. Much attention has been devoted to the development of effective surface modification strategies to enhance electronic coupling between the nanocrystals to promote charge carrier transport. Herein, we aim to attach benzenedithiol ligands onto the surface of CdSe nanocrystals in the "face-on" geometry to minimize the nanocrystal-nanocrystal or polymer-nanocrystal distance. Furthermore, the "electroactive" π-orbitals of the benzenedithiol are expected to further enhance the electronic coupling, which facilitates charge carrier dissociation and transport. The electron mobility of CdSe QD films was improved 20 times by tuning the ligand orientation, and high performance poly[2,6-(4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b']-dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)] (PCPDTBT):CdSe nanocrystal hybrid solar cells were also achieved, showing a highest power conversion efficiency of 4.18%. This research could open up a new pathway to improve further the performance of colloidal nanocrystal based solar cells.
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Affiliation(s)
- Weifei Fu
- State Key Laboratory of Silicon Materials, MOE Key Laboratory of Macromolecular Synthesis and Functionalization, Department of Polymer Science and Engineering, Zhejiang University , Hangzhou 310027, People's Republic of China
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39
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Pozner R, Lifshitz E, Peskin U. Charge transport-induced recoil and dissociation in double quantum dots. NANO LETTERS 2014; 14:6244-6249. [PMID: 25259800 DOI: 10.1021/nl502562g] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Colloidal quantum dots (CQDs) are free-standing nanostructures with chemically tunable electronic properties. This combination of properties offers intriguing new possibilities for nanoelectromechanical devices that were not explored yet. In this work, we consider a new scanning tunneling microscopy setup for measuring ligand-mediated effective interdot forces and for inducing motion of individual CQDs within an array. Theoretical analysis of a double quantum dot structure within this setup reveals for the first time voltage-induced interdot recoil and dissociation with pronounced changes in the current. Considering realistic microscopic parameters, our approach enables correlating the onset of mechanical motion under bias voltage with the effective ligand-mediated binding forces.
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Affiliation(s)
- Roni Pozner
- Schulich Faculty of Chemistry, ‡the Lise Meitner Center for Computational Quantum Chemistry, §Solid State Institute, and ∥Russell Berrie Nanotechnology Institute, Technion-Israel Institute of Technology , Haifa 32000, Israel
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40
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Pereira RN, Coutinho J, Niesar S, Oliveira TA, Aigner W, Wiggers H, Rayson MJ, Briddon PR, Brandt MS, Stutzmann M. Resonant electronic coupling enabled by small molecules in nanocrystal solids. NANO LETTERS 2014; 14:3817-3826. [PMID: 24845684 DOI: 10.1021/nl500932q] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The future exploitation of the exceptional properties of nanocrystal (NC) thin films deposited from liquid dispersions of nanoparticles relies upon our ability to produce films with improved electrical properties by simple and inexpensive means. Here, we demonstrate that the electronic conduction of solution-processed NC films can be strongly enhanced without the need of postdeposition treatments, via specific molecules adsorbed at the surfaces of adjacent NCs. This effect is demonstrated for Si NC films doped with the strong molecular oxidizing agent tetrafluoro-tetracyanoquinodimethane (F4-TCNQ). Density functional calculations were carried out with molecule-doped superlattice solid models. It is shown that, when populated by electrons, hybrid molecule/NC states edge (and may actually resonate with) the conduction-band states of the NC solid. This provides extra electronic connectivity across the NC network as the molecules effectively flatten the electronic potential barriers for electron transfer across the otherwise vacuum-filled network interstitialcies.
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Affiliation(s)
- Rui N Pereira
- Department of Physics and I3N, University of Aveiro , Campus Universitário de Santiago, 3810-193 Aveiro, Portugal
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41
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Heo SJ, Yoon S, Oh SH, Yoon DH, Kim HJ. Influence of high-pressure treatment on charge carrier transport in PbS colloidal quantum dot solids. NANOSCALE 2014; 6:903-907. [PMID: 24281416 DOI: 10.1039/c3nr03641c] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
We investigated the effects of high-pressure treatment on charge carrier transport in PbS colloidal quantum dot (CQD) solids. We applied high pressure to PbS CQD solids using nitrogen gas to reduce the inter-dot distance. Using this simple process, we obtained conductive PbS CQD solids. Terahertz time-domain spectroscopy was used to study charge carrier transport as a function of pressure. We found that the minimum pressure needed to increase the dielectric constant, conductivity, and carrier mobility was 4 MPa. All properties dramatically improved at 5 MPa; for example, the mobility increased from 0.13 cm(2) V(-1) s(-1) at 0.1 MPa to 0.91 cm(2) V(-1) s(-1) at 5 MPa. We propose this simple process as a nondestructive approach for making conductive PbS CQD solids that are free of chemical and physical defects.
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Affiliation(s)
- Seung Jin Heo
- School of Electrical and Electronic Engineering, Yonsei University, Seoul, Republic of Korea.
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42
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Sousa JCL, Vivas MG, Ferrari JL, Mendonca CR, Schiavon MA. Determination of particle size distribution of water-soluble CdTe quantum dots by optical spectroscopy. RSC Adv 2014. [DOI: 10.1039/c4ra05979d] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
In the present study, we report the synthesis of glutathione (GSH) capped CdTe quantum dots (QDs) using the one-pot approach as well as their optical properties.
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Affiliation(s)
- J. C. L. Sousa
- Grupo de Pesquisa em Química de Materiais (GPQM)
- Departamento de Ciências Naturais
- Universidade Federal de São João del-Rei
- 74 São João del-Rei, Brazil
| | - M. G. Vivas
- Instituto de Ciência e Tecnologia
- Universidade Federal de Alfenas
- Cidade Universitária
- Poços de Caldas, Brazil
- Instituto de Física de São Carlos
| | - J. L. Ferrari
- Grupo de Pesquisa em Química de Materiais (GPQM)
- Departamento de Ciências Naturais
- Universidade Federal de São João del-Rei
- 74 São João del-Rei, Brazil
| | - C. R. Mendonca
- Instituto de Física de São Carlos
- Universidade de São Paulo
- 13560-970 São Carlos, Brazil
| | - M. A. Schiavon
- Grupo de Pesquisa em Química de Materiais (GPQM)
- Departamento de Ciências Naturais
- Universidade Federal de São João del-Rei
- 74 São João del-Rei, Brazil
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43
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Bel Haj Mohamed N, Haouari M, Zaaboub Z, Nafoutti M, Hassen F, Maaref H, Ben Ouada H. Time resolved and temperature dependence of the radiative properties of thiol-capped CdS nanoparticles films. JOURNAL OF NANOPARTICLE RESEARCH : AN INTERDISCIPLINARY FORUM FOR NANOSCALE SCIENCE AND TECHNOLOGY 2014; 16:2242. [PMID: 24563613 PMCID: PMC3925497 DOI: 10.1007/s11051-013-2242-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2013] [Accepted: 12/30/2013] [Indexed: 05/07/2023]
Abstract
In this work, we present the temperature-dependence and time-resolved photoluminescence (PL) of CdS nanoparticles capped independently with three different ligands thiophenol, thioglycerol, and l-cysteine over a broad temperature range from 10 to 300 K. The respective nanoparticles sizes in the three systems studied in this work are 1.5, 4, and 2 nm as determined from X-ray diffraction (XRD). From the analysis of AFM images, it was found that the lateral particle sizes of capped CdS nanoparticles are greater than those deduced from XRD or optical absorption measurements. The aim of this study is the investigation of the impact of the organic ligands on the radiative recombination dynamics in organically capped CdS nanoparticles. From the PL study and based on the temperature-dependence and time-resolved emission spectroscopy, we conclude that the emission of CdS QDs film originates from recombination of the delocalized carriers in the internal core states with a small contribution of the localized carriers at the interface. The PL decay reveals a biexponential behavior for the entire three samples at all temperatures. One of the two exponential components decays rapidly with a time τ1 in the range 0.5-0.8 ns, whereas the other decays much more slowly, with a time τ2 in the range 1-3 ns. The weak activation energy (32-37 meV) deduced from the temperature dependence of the PL intensity suggests the involvement of shallow traps. The analysis of the experimental results reveals a relatively narrow size distribution, an efficient surface passivation, and a satisfactory thermal stability of CdS nanocrystals.
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Affiliation(s)
- N. Bel Haj Mohamed
- Laboratoire des Interfaces et des Matériaux avancés (LIMA), Faculté des Sciences de Monastir, Université Monastir, Avenue de l’environnement, 5019 Monastir, Tunisia
| | - M. Haouari
- Laboratoire des Interfaces et des Matériaux avancés (LIMA), Faculté des Sciences de Monastir, Université Monastir, Avenue de l’environnement, 5019 Monastir, Tunisia
| | - Z. Zaaboub
- Laboratoire de Micro-Optoélectronique et Nanostructures (LMON), Faculté des Sciences de Monastir, Université Monastir, Avenue de l’environnement, 5019 Monastir, Tunisia
| | - M. Nafoutti
- Laboratoire de Micro-Optoélectronique et Nanostructures (LMON), Faculté des Sciences de Monastir, Université Monastir, Avenue de l’environnement, 5019 Monastir, Tunisia
| | - F. Hassen
- Laboratoire de Micro-Optoélectronique et Nanostructures (LMON), Faculté des Sciences de Monastir, Université Monastir, Avenue de l’environnement, 5019 Monastir, Tunisia
| | - H. Maaref
- Laboratoire de Micro-Optoélectronique et Nanostructures (LMON), Faculté des Sciences de Monastir, Université Monastir, Avenue de l’environnement, 5019 Monastir, Tunisia
| | - H. Ben Ouada
- Laboratoire des Interfaces et des Matériaux avancés (LIMA), Faculté des Sciences de Monastir, Université Monastir, Avenue de l’environnement, 5019 Monastir, Tunisia
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44
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Kramer IJ, Sargent EH. The Architecture of Colloidal Quantum Dot Solar Cells: Materials to Devices. Chem Rev 2013; 114:863-82. [DOI: 10.1021/cr400299t] [Citation(s) in RCA: 401] [Impact Index Per Article: 36.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Affiliation(s)
- Illan J. Kramer
- Edward S. Rogers Department of Electrical & Computer Engineering, University of Toronto, 10 King’s College Road, Toronto, Ontario M5S 3G4, Canada
| | - Edward H. Sargent
- Edward S. Rogers Department of Electrical & Computer Engineering, University of Toronto, 10 King’s College Road, Toronto, Ontario M5S 3G4, Canada
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45
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Yang Y, Liu Z, Lian T. Bulk transport and interfacial transfer dynamics of photogenerated carriers in CdSe quantum dot solid electrodes. NANO LETTERS 2013; 13:3678-3683. [PMID: 23855506 DOI: 10.1021/nl401573x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Practical solar-to-fuel conversion applications of quantum-confined semiconductor crystals require their integration into electrodes. We show that photogenerated electrons in quantum dot solid electrodes can be transported to the aqueous interface to reduce methyl viologen with 100% quantum efficiency and an effective time constant of 12 ± 2 ps. The charge separated state had a half-life of 200 ± 10 ns, limited by hole transport within the solid.
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Affiliation(s)
- Ye Yang
- Department of Chemistry, Emory University, Atlanta, Georgia 30322, United States
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46
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Park Y, Koo C, Chen HY, Han A, Son DH. Ratiometric temperature imaging using environment-insensitive luminescence of Mn-doped core-shell nanocrystals. NANOSCALE 2013; 5:4944-50. [PMID: 23629731 PMCID: PMC3661212 DOI: 10.1039/c3nr00290j] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
We report a ratiometric temperature imaging method based on Mn luminescence from Mn-doped CdS-ZnS nanocrystals (NCs) with controlled doping location, which is designed to exhibit strong temperature dependence of the spectral lineshape while being insensitive to the surrounding chemical environment. Ratiometric thermometry on the Mn luminescence spectrum was performed by using Mn-doped CdS-ZnS core-shell NCs that have a large local lattice strain on the Mn site, which results in the enhanced temperature dependence of the bandwidth and peak position. The Mn luminescence spectral lineshape is highly robust with respect to the change in the polarity, phase and pH of the surrounding medium and aggregation of the NCs, showing great potential in temperature imaging under chemically heterogeneous environment. The temperature sensitivity (ΔIR/IR = 0.5%/K at 293 K, IR = intensity ratio at two different wavelengths) is highly linear in a wide range of temperatures from cryogenic to above-ambient temperatures. We demonstrate the surface temperature imaging of a cryo-cooling device showing a temperature variation of >200 K by imaging the luminescence of the NC film formed by simple spin coating, taking advantage of the environment-insensitive luminescence.
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Affiliation(s)
- Yerok Park
- Department of Chemistry, Texas A&M University, College Station, Texas 77842, United States
| | - Chiwan Koo
- Department of Biomedical Engineering, Texas A&M University, College Station, Texas 77843, United States
| | - Hsiang-Yun Chen
- Department of Chemistry, Texas A&M University, College Station, Texas 77842, United States
| | - Arum Han
- Department of Biomedical Engineering, Texas A&M University, College Station, Texas 77843, United States
- Department of Electrical and Computer Engineering, Texas A&M University, College Station, Texas 77843, United States
| | - Dong Hee Son
- Department of Chemistry, Texas A&M University, College Station, Texas 77842, United States
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47
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Guyot-Sionnest P, Lhuillier E, Liu H. A mirage study of CdSe colloidal quantum dot films, Urbach tail, and surface states. J Chem Phys 2013; 137:154704. [PMID: 23083181 DOI: 10.1063/1.4758318] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Thermal deflection spectroscopy allows to measure very small absorption and uncovers absorption tails extending well below the bulk bandgap energy for CdSe quantum dots films after ligand exchange by sulfide. In this monodispersed system, the redshift, the broadening, and the absorption tails cannot be solely attributed to electronic coupling between the dots. Instead, mixing of hole states from the quantum dot and surface is proposed to dominate the changes of the interband spectra at the absorption edge.
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Affiliation(s)
- Philippe Guyot-Sionnest
- James Franck Institute, The University of Chicago, 929 E. 57th Street, Chicago, Illinois 60637, USA
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48
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Korala L, Wang Z, Liu Y, Maldonado S, Brock SL. Uniform thin films of CdSe and CdSe(ZnS) core(shell) quantum dots by sol-gel assembly: enabling photoelectrochemical characterization and electronic applications. ACS NANO 2013; 7:1215-1223. [PMID: 23350924 PMCID: PMC3590068 DOI: 10.1021/nn304563j] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Optoelectronic properties of quantum dot (QD) films are limited by (1) poor interfacial chemistry and (2) nonradiative recombination due to surface traps. To address these performance issues, sol-gel methods are applied to fabricate thin films of CdSe and core(shell) CdSe(ZnS) QDs. High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) imaging with chemical analysis confirms that the surface of the QDs in the sol-gel thin films are chalcogen-rich, consistent with an oxidative-induced gelation mechanism in which connectivity is achieved by formation of dichalcogenide covalent linkages between particles. The ligand removal and assembly process is probed by thermogravimetric, spectroscopic, and microscopic studies. Further enhancement of interparticle coupling via mild thermal annealing, which removes residual ligands and reinforces QD connectivity, results in QD sol-gel thin films with superior charge transport properties, as shown by a dramatic enhancement of electrochemical photocurrent under white light illumination relative to thin films composed of ligand-capped QDs. A more than 2-fold enhancement in photocurrent, and a further increase in photovoltage can be achieved by passivation of surface defects via overcoating with a thin ZnS shell. The ability to tune interfacial and surface characteristics for the optimization of photophysical properties suggests that the sol-gel approach may enable formation of QD thin films suitable for a range of optoelectronic applications.
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Affiliation(s)
- Lasantha Korala
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, USA
| | - Zhijie Wang
- Chemistry Department, University of Michigan, Ann Arbor, Michigan 48109, USA
| | - Yi Liu
- Electron Microscopy Facility, Oregon State University, Corvallis, Oregon 87331, USA
| | - Stephen Maldonado
- Chemistry Department, University of Michigan, Ann Arbor, Michigan 48109, USA
| | - Stephanie L. Brock
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, USA
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49
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Foos EE. The Complex Interaction of Spectroscopic Shifts and Electronic Properties in Semiconductor Nanocrystal Films. J Phys Chem Lett 2013; 4:625-632. [PMID: 26281877 DOI: 10.1021/jz3021364] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Absorption spectroscopy has traditionally served as a powerful technique for the study of solution synthesized semiconductor nanocrystals, enabling information on the size, dispersity, concentration, and overall quality of a sample to be obtained quickly and easily. When thin, densely packed films of these materials are produced through ligand exchange, spectroscopic shifts to both higher and lower energy are observed. Reduction of the internanocrystal distance can result in both a change to the overall dielectric constant of the film as well as increased electronic coupling, producing a redshift. At the same time, surface oxidation has the effect of increasing the confinement, producing a blueshift. This Perspective focuses on PbSe, a material of current interest, and the potential for correlating these spectroscopic shifts to optoelectronic properties, highlighting both recent work in the literature and areas in need of additional study.
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Affiliation(s)
- Edward E Foos
- Chemistry Division, Naval Research Laboratory, Washington, DC 20375, United States
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50
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Zhitomirsky D, Furukawa M, Tang J, Stadler P, Hoogland S, Voznyy O, Liu H, Sargent EH. N-type colloidal-quantum-dot solids for photovoltaics. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2012; 24:6181-5. [PMID: 22968808 DOI: 10.1002/adma.201202825] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2012] [Revised: 08/16/2012] [Indexed: 05/20/2023]
Abstract
N-type PbS colloidal-quantum-dot (CQD) films are fabricated using a controlled halide chemical treatment, applied in an inert processing ambient environment. The new materials exhibit a mobility of 0.1 cm(2) V(-1) s(-1) . The halogen ions serve both as a passivating agent and n-dope the films via substitution at surface chalcogen sites. The majority electron concentration across the range 10(16) to 10(18) cm(-3) is varied systematically.
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Affiliation(s)
- David Zhitomirsky
- Department of Electrical and Computer Engineering, University of Toronto, 10 King's College Road, Toronto, Ontario, M5S 3G4, Canada
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