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Cho K, Park Y, Jo H, Seo S, Moon J, Lee SJ, Park SY, Yoon SJ, Park J. Identification and Dynamics of Microsecond Long-Lived Charge Carriers for CsPbBr 3 Perovskite Quantum Dots, Featuring Ambient Long-Term Stability. J Phys Chem Lett 2024; 15:5795-5803. [PMID: 38780120 DOI: 10.1021/acs.jpclett.4c01024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/25/2024]
Abstract
We analyze the stability and photophysical dynamics of CsPbBr3 perovskite quantum dots (PeQDs), fabricated under mild synthetic conditions and embedded in an amorphous silica (SiOx) matrix (CsPbBr3@SiOx), underscoring their sustained performance in ambient conditions for over 300 days with minimal optical degradation. However, this stability comes at the cost of a reduced photoluminescence efficiency. Time-resolved spectroscopic analyses, including flash-photolysis time-resolved microwave conductivity and time-resolved photoluminescence, show that excitons in CsPbBr3@SiOx films decay within 2.5 ns, while charge carriers recombine over approximately 230 ns. This longevity of the charge carriers is due to photoinduced electron transfer to the SiOx matrix, enabling hole retention. The measured hole mobility in these PeQDs is 0.880 cm2 V-1 s-1, underscoring their potential in optoelectronic applications. This study highlights the role of the silica matrix in enhancing the durability of PeQDs in humid environments and modifying exciton dynamics and photoluminescence, providing valuable insights for developing robust optoelectronic materials.
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Affiliation(s)
- Kayoung Cho
- Department of Chemistry and Nanoscience, Ewha Womans University, Seoul 03760, Republic of Korea
| | - Youmin Park
- Department of Chemistry and Nanoscience, Ewha Womans University, Seoul 03760, Republic of Korea
| | - Hyeonyeong Jo
- Department of Chemistry, Yeungnam University, Gyeongsan 38541, Republic of Korea
| | - Sumi Seo
- Department of Chemistry, Yeungnam University, Gyeongsan 38541, Republic of Korea
| | - Jiyoung Moon
- Department of Chemistry and Nanoscience, Ewha Womans University, Seoul 03760, Republic of Korea
| | - Soo Jeong Lee
- Department of Chemistry, Yeungnam University, Gyeongsan 38541, Republic of Korea
| | - Seong Yeon Park
- Department of Chemistry, Yeungnam University, Gyeongsan 38541, Republic of Korea
| | - Seog Joon Yoon
- Department of Chemistry, Yeungnam University, Gyeongsan 38541, Republic of Korea
| | - JaeHong Park
- Department of Chemistry and Nanoscience, Ewha Womans University, Seoul 03760, Republic of Korea
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2
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Rodosthenous P, Skibinsky-Gitlin ES, Rodriguez-Bolivar S, Califano M, Gomez-Campos FM. Band-like transport in 'green' quantum dot films: the effect of composition and stoichiometry. J Chem Phys 2022; 156:104704. [DOI: 10.1063/5.0078375] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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3
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Wang W, Zhang M, Pan Z, Biesold GM, Liang S, Rao H, Lin Z, Zhong X. Colloidal Inorganic Ligand-Capped Nanocrystals: Fundamentals, Status, and Insights into Advanced Functional Nanodevices. Chem Rev 2021; 122:4091-4162. [PMID: 34968050 DOI: 10.1021/acs.chemrev.1c00478] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Colloidal nanocrystals (NCs) are intriguing building blocks for assembling various functional thin films and devices. The electronic, optoelectronic, and thermoelectric applications of solution-processed, inorganic ligand (IL)-capped colloidal NCs are especially promising as the performance of related devices can substantially outperform their organic ligand-capped counterparts. This in turn highlights the significance of preparing IL-capped NC dispersions. The replacement of initial bulky and insulating ligands capped on NCs with short and conductive inorganic ones is a critical step in solution-phase ligand exchange for preparing IL-capped NCs. Solution-phase ligand exchange is extremely appealing due to the highly concentrated NC inks with completed ligand exchange and homogeneous ligand coverage on the NC surface. In this review, the state-of-the-art of IL-capped NCs derived from solution-phase inorganic ligand exchange (SPILE) reactions are comprehensively reviewed. First, a general overview of the development and recent advancements of the synthesis of IL-capped colloidal NCs, mechanisms of SPILE, elementary reaction principles, surface chemistry, and advanced characterizations is provided. Second, a series of important factors in the SPILE process are offered, followed by an illustration of how properties of NC dispersions evolve after ILE. Third, surface modifications of perovskite NCs with use of inorganic reagents are overviewed. They are necessary because perovskite NCs cannot withstand polar solvents or undergo SPILE due to their soft ionic nature. Fourth, an overview of the research progresses in utilizing IL-capped NCs for a wide range of applications is presented, including NC synthesis, NC solid and film fabrication techniques, field effect transistors, photodetectors, photovoltaic devices, thermoelectric, and photoelectrocatalytic materials. Finally, the review concludes by outlining the remaining challenges in this field and proposing promising directions to further promote the development of IL-capped NCs in practical application in the future.
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Affiliation(s)
- Wenran Wang
- Key Laboratory for Biobased Materials and Energy of Ministry of Education, College of Materials and Energy, South China Agricultural University, 483 Wushan Road, Guangzhou 510642, China.,School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, United States.,Guangdong Laboratory for Lingnan Modern Agriculture, Guangzhou 510642, China
| | - Meng Zhang
- School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
| | - Zhenxiao Pan
- Key Laboratory for Biobased Materials and Energy of Ministry of Education, College of Materials and Energy, South China Agricultural University, 483 Wushan Road, Guangzhou 510642, China.,Guangdong Laboratory for Lingnan Modern Agriculture, Guangzhou 510642, China
| | - Gill M Biesold
- School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
| | - Shuang Liang
- School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
| | - Huashang Rao
- Key Laboratory for Biobased Materials and Energy of Ministry of Education, College of Materials and Energy, South China Agricultural University, 483 Wushan Road, Guangzhou 510642, China.,Guangdong Laboratory for Lingnan Modern Agriculture, Guangzhou 510642, China
| | - Zhiqun Lin
- School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
| | - Xinhua Zhong
- Key Laboratory for Biobased Materials and Energy of Ministry of Education, College of Materials and Energy, South China Agricultural University, 483 Wushan Road, Guangzhou 510642, China.,Guangdong Laboratory for Lingnan Modern Agriculture, Guangzhou 510642, China
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4
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Grimaldi G, van den Brom MJ, du Fossé I, Crisp RW, Kirkwood N, Gudjonsdottir S, Geuchies JJ, Kinge S, Siebbeles LDA, Houtepen AJ. Engineering the Band Alignment in QD Heterojunction Films via Ligand Exchange. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2019; 123:29599-29608. [PMID: 31867087 PMCID: PMC6913897 DOI: 10.1021/acs.jpcc.9b09470] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2019] [Revised: 11/18/2019] [Indexed: 05/24/2023]
Abstract
Colloidal quantum dots (QDs) allow great flexibility in the design of optoelectronic devices, thanks to their size-dependent optical and electronic properties and the possibility to fabricate thin films with solution-based processing. In particular, in QD-based heterojunctions, the band gap of both components can be controlled by varying the size of the QDs. However, control over the band alignment between the two materials is required to tune the dynamics of carrier transfer across a heterostructure. We demonstrate that ligand exchange strategies can be used to control the band alignment of PbSe and CdSe QDs in a mixed QD solid, shifting it from a type-I to a type-II alignment. The change in alignment is observed in both spectroelectrochemical and transient absorption measurements, leading to a change in the energy of the conduction band edges in the two materials and in the direction of electron transfer upon photoexcitation. Our work demonstrates the possibility to tune the band offset of QD heterostructures via control of the chemical species passivating the QD surface, allowing full control over the energetics of the heterostructure without requiring changes in the QD composition.
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Affiliation(s)
- Gianluca Grimaldi
- Optoelectronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Mark J. van den Brom
- Optoelectronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Indy du Fossé
- Optoelectronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Ryan W. Crisp
- Optoelectronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Nicholas Kirkwood
- Optoelectronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Solrun Gudjonsdottir
- Optoelectronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Jaco J. Geuchies
- Optoelectronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Sachin Kinge
- Toyota
Motor Europe, Materials Research & Development, Hoge Wei 33, B-1930 Zaventem, Belgium
| | - Laurens D. A. Siebbeles
- Optoelectronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Arjan J. Houtepen
- Optoelectronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
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5
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Marino E, Balazs DM, Crisp RW, Hermida-Merino D, Loi MA, Kodger TE, Schall P. Controlling Superstructure-Property Relationships via Critical Casimir Assembly of Quantum Dots. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2019; 123:13451-13457. [PMID: 31205576 PMCID: PMC6558640 DOI: 10.1021/acs.jpcc.9b02033] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/03/2019] [Revised: 04/26/2019] [Indexed: 05/17/2023]
Abstract
The assembly of colloidal quantum dots (QDs) into dense superstructures holds great promise for the development of novel optoelectronic devices. Several assembly techniques have been explored; however, achieving direct and precise control over the interparticle potential that controls the assembly has proven to be challenging. Here, we exploit the application of critical Casimir forces to drive the growth of QDs into superstructures. We show that the exquisite temperature-dependence of the critical Casimir potential offers new opportunities to control the assembly process and morphology of the resulting QD superstructures. The direct assembly control allows us to elucidate the relation between structural, optical, and conductive properties of the critical Casimir-grown QD superstructures. We find that the choice of the temperature setting the interparticle potential plays a central role in maximizing charge percolation across QD thin-films. These results open up new directions for controlling the assembly of nanostructures and their optoelectronic properties.
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Affiliation(s)
- Emanuele Marino
- Van
der Waals—Zeeman Institute, University
of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands
| | - Daniel M. Balazs
- Zernike
Institute for Advanced Materials, University
of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Ryan W. Crisp
- Chemical
Engineering, Optoelectronic Materials, Delft
University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | | | - Maria A. Loi
- Zernike
Institute for Advanced Materials, University
of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Thomas E. Kodger
- Van
der Waals—Zeeman Institute, University
of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands
- Physical
Chemistry and Soft Matter, Wageningen University
& Research, Stippeneng 4, 6708 WE Wageningen, The Netherlands
| | - Peter Schall
- Van
der Waals—Zeeman Institute, University
of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands
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6
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Abstract
The use of solution-processed photovoltaics is a low cost, low material-consuming way to harvest abundant solar energy. Organic semiconductors based on perovskite or colloidal quantum dot photovoltaics have been well developed in recent years; however, stability is still an important issue for these photovoltaic devices. By combining solution processing, chemical treatment, and sintering technology, compact and efficient CdTe nanocrystal (NC) solar cells can be fabricated with high stability by optimizing the architecture of devices. Here, we review the progress on solution-processed CdTe NC-based photovoltaics. We focus particularly on NC materials and the design of devices that provide a good p–n junction quality, a graded bandgap for extending the spectrum response, and interface engineering to decrease carrier recombination. We summarize the progress in this field and give some insight into device processing, including element doping, new hole transport material application, and the design of new devices.
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7
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Zhao K, Niu W, Wang Y, Zhang S. Electrophilic substitution reaction as a facile and general approach for reactive removal of native ligands from nanocrystals surface. NANOTECHNOLOGY 2019; 30:015701. [PMID: 30359328 DOI: 10.1088/1361-6528/aae682] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Surface property that strongly affects physical and chemical performances of inorganic nanocrystals (NCs) is a key enabler for NCs applications. Here, we report a facile, versatile and general strategy for reactive removal of NCs surface ligands based on electrophilic substitution reaction, in which an electrophile directly reacts with the electron-rich coordinating headgroup of surface-tethered ligands to form a non-coordinating product. This process leads to the break of NC-ligand bond, thereby achieving reactive removal of surface ligands. Based on this strategy, various hydrophobic NCs with different compositions and morphologies can be transferred into polar and hydrophilic media while preserving their size and shape. More importantly, the treated NCs present a great improvement in catalytic and biological performances in comparison with the untreated counterparts. This work not only provides a versatile ligand removal strategy for NCs surface modification but also opens up more opportunities for applications in the fields of electronics, catalysis and biotechnology.
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Affiliation(s)
- Kai Zhao
- State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian, 116024, People's Republic of China
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8
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Crisp RW, Kirkwood N, Grimaldi G, Kinge S, Siebbeles LDA, Houtepen AJ. Highly Photoconductive InP Quantum Dots Films and Solar Cells. ACS APPLIED ENERGY MATERIALS 2018; 1:6569-6576. [PMID: 30506040 PMCID: PMC6259048 DOI: 10.1021/acsaem.8b01453] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/30/2018] [Accepted: 10/23/2018] [Indexed: 05/05/2023]
Abstract
InP and InZnP colloidal quantum dots (QDs) are promising materials for application in light-emitting devices, transistors, photovoltaics, and photocatalytic cells. In addition to possessing an appropriate bandgap, high absorption coefficient, and high bulk carrier mobilities, the intrinsic toxicity of InP and InZnP is much lower than for competing QDs that contain Cd or Pb-providing a potentially safer commercial product. However, compared to other colloidal QDs, InP QDs remain sparsely used in devices and their electronic transport properties are largely unexplored. Here, we use time-resolved microwave conductivity measurements to study charge transport in films of InP and InZnP colloidal quantum dots capped with a variety of short ligands. We find that transport in InP QDs is dominated by trapping effects, which are mitigated in InZnP QDs. We improve charge carrier mobilities with a range of ligand-exchange treatments and for the best treatments reach mobilities and lifetimes on par with those of PbS QD films used in efficient solar cells. To demonstrate the device-grade quality of these films, we construct solar cells based on InP & InZnP QDs with power conversion efficiencies of 0.65 and 1.2%, respectively. This represents a large step forward in developing Cd- and Pb-free next-generation optoelectronic devices.
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Affiliation(s)
- Ryan W. Crisp
- Chemical
Engineering Department, Delft University
of Technology, Van der Maasweg 9, Delft2629 HZ , The Netherlands
| | - Nicholas Kirkwood
- Chemical
Engineering Department, Delft University
of Technology, Van der Maasweg 9, Delft2629 HZ , The Netherlands
| | - Gianluca Grimaldi
- Chemical
Engineering Department, Delft University
of Technology, Van der Maasweg 9, Delft2629 HZ , The Netherlands
| | - Sachin Kinge
- Toyota
Motor Europe, Materials Research & Development, Hoge Wei 33, Zaventem B-1930, Belgium
| | - Laurens D. A. Siebbeles
- Chemical
Engineering Department, Delft University
of Technology, Van der Maasweg 9, Delft2629 HZ , The Netherlands
| | - Arjan J. Houtepen
- Chemical
Engineering Department, Delft University
of Technology, Van der Maasweg 9, Delft2629 HZ , The Netherlands
- . Website: www.tudelft.nl/cheme/houtepengroup
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9
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Kirkwood N, Monchen JOV, Crisp RW, Grimaldi G, Bergstein HAC, du Fossé I, van der Stam W, Infante I, Houtepen AJ. Finding and Fixing Traps in II-VI and III-V Colloidal Quantum Dots: The Importance of Z-Type Ligand Passivation. J Am Chem Soc 2018. [PMID: 30375226 DOI: 10.1021/ja-2018-07783h] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/17/2023]
Abstract
Energy levels in the band gap arising from surface states can dominate the optical and electronic properties of semiconductor nanocrystal quantum dots (QDs). Recent theoretical work has predicted that such trap states in II-VI and III-V QDs arise only from two-coordinated anions on the QD surface, offering the hypothesis that Lewis acid (Z-type) ligands should be able to completely passivate these anionic trap states. In this work, we provide experimental support for this hypothesis by demonstrating that Z-type ligation is the primary cause of PL QY increase when passivating undercoordinated CdTe QDs with various metal salts. Optimized treatments with InCl3 or CdCl2 afford a near-unity (>90%) photoluminescence quantum yield (PL QY), whereas other metal halogen or carboxylate salts provide a smaller increase in PL QY as a result of weaker binding or steric repulsion. The addition of non-Lewis acidic ligands (amines, alkylammonium chlorides) systematically gives a much smaller but non-negligible increase in the PL QY. We discuss possible reasons for this result, which points toward a more complex and dynamic QD surface. Finally we show that Z-type metal halide ligand treatments also lead to a strong increase in the PL QY of CdSe, CdS, and InP QDs and can increase the efficiency of sintered CdTe solar cells. These results show that surface anions are the dominant source of trap states in II-VI and III-V QDs and that passivation with Lewis acidic Z-type ligands is a general strategy to fix those traps. Our work also provides a method to tune the PL QY of QD samples from nearly zero up to near-unity values, without the need to grow epitaxial shells.
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Affiliation(s)
- Nicholas Kirkwood
- Optoelectronic Materials Section, Faculty of Applied Sciences , Delft University of Technology , Van der Maasweg 9 , 2629 HZ Delft , The Netherlands
| | - Julius O V Monchen
- Optoelectronic Materials Section, Faculty of Applied Sciences , Delft University of Technology , Van der Maasweg 9 , 2629 HZ Delft , The Netherlands
| | - Ryan W Crisp
- Optoelectronic Materials Section, Faculty of Applied Sciences , Delft University of Technology , Van der Maasweg 9 , 2629 HZ Delft , The Netherlands
| | - Gianluca Grimaldi
- Optoelectronic Materials Section, Faculty of Applied Sciences , Delft University of Technology , Van der Maasweg 9 , 2629 HZ Delft , The Netherlands
| | - Huub A C Bergstein
- Optoelectronic Materials Section, Faculty of Applied Sciences , Delft University of Technology , Van der Maasweg 9 , 2629 HZ Delft , The Netherlands
| | - Indy du Fossé
- Optoelectronic Materials Section, Faculty of Applied Sciences , Delft University of Technology , Van der Maasweg 9 , 2629 HZ Delft , The Netherlands
| | - Ward van der Stam
- Optoelectronic Materials Section, Faculty of Applied Sciences , Delft University of Technology , Van der Maasweg 9 , 2629 HZ Delft , The Netherlands
| | - Ivan Infante
- Department of Theoretical Chemistry, Faculty of Science , Vrije Universiteit Amsterdam , de Boelelaan 1083 , 1081 HV Amsterdam , The Netherlands
| | - Arjan J Houtepen
- Optoelectronic Materials Section, Faculty of Applied Sciences , Delft University of Technology , Van der Maasweg 9 , 2629 HZ Delft , The Netherlands
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10
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Kirkwood N, Monchen JOV, Crisp RW, Grimaldi G, Bergstein HAC, du Fossé I, van der Stam W, Infante I, Houtepen AJ. Finding and Fixing Traps in II-VI and III-V Colloidal Quantum Dots: The Importance of Z-Type Ligand Passivation. J Am Chem Soc 2018; 140:15712-15723. [PMID: 30375226 PMCID: PMC6257620 DOI: 10.1021/jacs.8b07783] [Citation(s) in RCA: 93] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
![]()
Energy levels in
the band gap arising from surface states can dominate
the optical and electronic properties of semiconductor nanocrystal
quantum dots (QDs). Recent theoretical work has predicted that such
trap states in II–VI and III–V QDs arise only from two-coordinated
anions on the QD surface, offering the hypothesis that Lewis acid
(Z-type) ligands should be able to completely passivate these anionic
trap states. In this work, we provide experimental support for this
hypothesis by demonstrating that Z-type ligation is the primary cause
of PL QY increase when passivating undercoordinated CdTe QDs with
various metal salts. Optimized treatments with InCl3 or
CdCl2 afford a near-unity (>90%) photoluminescence quantum
yield (PL QY), whereas other metal halogen or carboxylate salts provide
a smaller increase in PL QY as a result of weaker binding or steric
repulsion. The addition of non-Lewis acidic ligands (amines, alkylammonium
chlorides) systematically gives a much smaller but non-negligible
increase in the PL QY. We discuss possible reasons for this result,
which points toward a more complex and dynamic QD surface. Finally
we show that Z-type metal halide ligand treatments also lead to a
strong increase in the PL QY of CdSe, CdS, and InP QDs and can increase
the efficiency of sintered CdTe solar cells. These results show that
surface anions are the dominant source of trap states in II–VI
and III–V QDs and that passivation with Lewis acidic Z-type
ligands is a general strategy to fix those traps. Our work also provides
a method to tune the PL QY of QD samples from nearly zero up to near-unity
values, without the need to grow epitaxial shells.
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Affiliation(s)
- Nicholas Kirkwood
- Optoelectronic Materials Section, Faculty of Applied Sciences , Delft University of Technology , Van der Maasweg 9 , 2629 HZ Delft , The Netherlands
| | - Julius O V Monchen
- Optoelectronic Materials Section, Faculty of Applied Sciences , Delft University of Technology , Van der Maasweg 9 , 2629 HZ Delft , The Netherlands
| | - Ryan W Crisp
- Optoelectronic Materials Section, Faculty of Applied Sciences , Delft University of Technology , Van der Maasweg 9 , 2629 HZ Delft , The Netherlands
| | - Gianluca Grimaldi
- Optoelectronic Materials Section, Faculty of Applied Sciences , Delft University of Technology , Van der Maasweg 9 , 2629 HZ Delft , The Netherlands
| | - Huub A C Bergstein
- Optoelectronic Materials Section, Faculty of Applied Sciences , Delft University of Technology , Van der Maasweg 9 , 2629 HZ Delft , The Netherlands
| | - Indy du Fossé
- Optoelectronic Materials Section, Faculty of Applied Sciences , Delft University of Technology , Van der Maasweg 9 , 2629 HZ Delft , The Netherlands
| | - Ward van der Stam
- Optoelectronic Materials Section, Faculty of Applied Sciences , Delft University of Technology , Van der Maasweg 9 , 2629 HZ Delft , The Netherlands
| | - Ivan Infante
- Department of Theoretical Chemistry, Faculty of Science , Vrije Universiteit Amsterdam , de Boelelaan 1083 , 1081 HV Amsterdam , The Netherlands
| | - Arjan J Houtepen
- Optoelectronic Materials Section, Faculty of Applied Sciences , Delft University of Technology , Van der Maasweg 9 , 2629 HZ Delft , The Netherlands
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11
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Abstract
From a niche field over 30 years ago, quantum dots (QDs) have developed into viable materials for many commercial optoelectronic devices. We discuss the advancements in Pb-based QD solar cells (QDSCs) from a viewpoint of the pathways an excited state can take when relaxing back to the ground state. Systematically understanding the fundamental processes occurring in QDs has led to improvements in solar cell efficiency from ~3% to over 13% in 8 years. We compile data from ~200 articles reporting functioning QDSCs to give an overview of the current limitations in the technology. We find that the open circuit voltage limits the device efficiency and propose some strategies for overcoming this limitation.
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12
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Azzaro MS, Dodin A, Zhang DY, Willard AP, Roberts ST. Exciton-Delocalizing Ligands Can Speed Up Energy Migration in Nanocrystal Solids. NANO LETTERS 2018; 18:3259-3270. [PMID: 29652509 DOI: 10.1021/acs.nanolett.8b01079] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Researchers have long sought to use surface ligands to enhance energy migration in nanocrystal solids by decreasing the physical separation between nanocrystals and strengthening their electronic coupling. Exciton-delocalizing ligands, which possess frontier molecular orbitals that strongly mix with nanocrystal band-edge states, are well-suited for this role because they can facilitate carrier-wave function extension beyond the nanocrystal core, reducing barriers for energy transfer. This report details the use of the exciton-delocalizing ligand phenyldithiocarbamate (PDTC) to tune the transport rate and diffusion length of excitons in CdSe nanocrystal solids. A film composed of oleate-terminated CdSe nanocrystals is subjected to a solid-state ligand exchange to replace oleate with PDTC. Exciton migration in the films is subsequently investigated by femtosecond transient absorption. Our experiments indicate that the treatment of nanocrystal films with PDTC leads to rapid (∼400 fs) downhill energy migration (∼80 meV), while no such migration occurs in oleate-capped films. Kinetic Monte Carlo simulations allow us to extract both rates and length scales for exciton diffusion in PDTC-treated films. These simulations reproduce dynamics observed in transient absorption measurements over a range of temperatures and confirm excitons hop via a Miller-Abrahams mechanism. Importantly, our experiments and simulations show PDTC treatment increases the exciton hopping rate to 200 fs, an improvement of 5 orders of magnitude relative to oleate-capped films. This exciton hopping rate stands as one of the fastest determined for CdSe solids. The facile, room-temperature processing and improved transport properties offered by the solid-state exchange of exciton-delocalizing ligands show they offer promise for the construction of strongly coupled nanocrystal arrays.
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Affiliation(s)
| | - Amro Dodin
- Department of Chemistry , Massachusetts Institute of Technology , Cambridge , Massachusetts 02139 , United States
| | | | - Adam P Willard
- Department of Chemistry , Massachusetts Institute of Technology , Cambridge , Massachusetts 02139 , United States
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13
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Wang J, Yu H, Wang T, Qiao Y, Feng Y, Chen K. Composition-Dependent Aspect Ratio and Photoconductivity of Ternary (Bi xSb 1-x) 2S 3 Nanorods. ACS APPLIED MATERIALS & INTERFACES 2018; 10:7334-7343. [PMID: 29384357 DOI: 10.1021/acsami.7b17253] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The chemical composition, size and shape, and surface engineering play key roles in the performance of electronic, optoelectronic, and energy devices. V2VI3 (V = Sb, Bi; VI = S, Se) group materials are actively studied in these fields. In this paper, we introduce a colloidal method to synthesize uniform ternary (BixSb1-x)2S3 (0 < x < 1) nanorods. These nanorods show composition-dependent aspect ratios, enabling their composition, size, and shape control by varying Bi/Sb precursor ratios. It is found that the surface passivation by various thiols (L-SH) efficiently enhances the photoconductivity and optical responsive capability of (BixSb1-x)2S3 nanorods when used as active materials in indium tin oxide (ITO)/(BixSb1-x)2S3/ITO optoelectronic devices. Meanwhile, the increase of Sb content causes a gradual deterioration of photoconductivity of thiol-passivated nanorods. We propose that the thiol passivation is able to reduce the number of S vacancies, which act as the recombination centers (trapped states) for photogenerated electrons and holes, and thus boosts the carrier transport in (BixSb1-x)2S3 nanorods, and in particular that the composition-related conductivity deterioration is attributed to the increase of unpassivated S vacancies and surface oxidation due to the rise of Sb content.
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Affiliation(s)
- Junli Wang
- School of Materials Science & Engineering, Jiangsu University , Zhenjiang 212013, P. R. China
| | - Hongsong Yu
- School of Materials Science & Engineering, Jiangsu University , Zhenjiang 212013, P. R. China
| | - Tingting Wang
- School of Materials Science & Engineering, Jiangsu University , Zhenjiang 212013, P. R. China
| | - Yajie Qiao
- School of Materials Science & Engineering, Jiangsu University , Zhenjiang 212013, P. R. China
| | - Ying Feng
- School of Materials Science & Engineering, Jiangsu University , Zhenjiang 212013, P. R. China
| | - Kangmin Chen
- School of Materials Science & Engineering, Jiangsu University , Zhenjiang 212013, P. R. China
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14
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Chistyakov AA, Zvaigzne MA, Nikitenko VR, Tameev AR, Martynov IL, Prezhdo OV. Optoelectronic Properties of Semiconductor Quantum Dot Solids for Photovoltaic Applications. J Phys Chem Lett 2017; 8:4129-4139. [PMID: 28799772 DOI: 10.1021/acs.jpclett.7b00671] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Quantum dot (QD) solids represent a new type of condensed matter drawing high fundamental and applied interest. Quantum confinement in individual QDs, combined with macroscopic scale whole materials, leads to novel exciton and charge transfer features that are particularly relevant to optoelectronic applications. This Perspective discusses the structure of semiconductor QD solids, optical and spectral properties, charge carrier transport, and photovoltaic applications. The distance between adjacent nanoparticles and surface ligands influences greatly electrostatic interactions between QDs and, hence, charge and energy transfer. It is almost inevitable that QD solids exhibit energetic disorder that bears many similarities to disordered organic semiconductors, with charge and exciton transport described by the multiple trapping model. QD solids are synthesized at low cost from colloidal solutions by casting, spraying, and printing. A judicious selection of a layer sequence involving QDs with different size, composition, and ligands can be used to harvest sunlight over a wide spectral range, leading to inexpensive and efficient photovoltaic devices.
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Affiliation(s)
- A A Chistyakov
- National Research Nuclear University "MEPhI" (Moscow Engineering Physics Institute) , Moscow 115409, Russia
| | - M A Zvaigzne
- National Research Nuclear University "MEPhI" (Moscow Engineering Physics Institute) , Moscow 115409, Russia
| | - V R Nikitenko
- National Research Nuclear University "MEPhI" (Moscow Engineering Physics Institute) , Moscow 115409, Russia
| | - A R Tameev
- National Research Nuclear University "MEPhI" (Moscow Engineering Physics Institute) , Moscow 115409, Russia
- A.N. Frumkin Institute of Physical Chemistry and Electrochemistry of the Russian Academy of Sciences , 31-building 4 Leninsky Prospect, Moscow 119071, Russia
| | - I L Martynov
- National Research Nuclear University "MEPhI" (Moscow Engineering Physics Institute) , Moscow 115409, Russia
| | - O V Prezhdo
- National Research Nuclear University "MEPhI" (Moscow Engineering Physics Institute) , Moscow 115409, Russia
- Department of Chemistry, Department of Physics, and Department of Astronomy, University of Southern California , Los Angeles, California 90089, United States
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15
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Valentine AJS, Talapin DV, Mazziotti DA. Orbitals, Occupation Numbers, and Band Structure of Short One-Dimensional Cadmium Telluride Polymers. J Phys Chem A 2017; 121:3142-3147. [PMID: 28406638 DOI: 10.1021/acs.jpca.7b00858] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Recent work found that soldering CdTe quantum dots together with a molecular CdTe polymer yielded field-effect transistors with much greater electron mobility than quantum dots alone. We present a computational study of the CdTe polymer using the active-space variational two-electron reduced density matrix (2-RDM) method. While analogous complete active-space self-consistent field (CASSCF) methods scale exponentially with the number of active orbitals, the active-space variational 2-RDM method exhibits polynomial scaling. A CASSCF calculation using the (48o,64e) active space studied in this paper requires 1024 determinants and is therefore intractable, while the variational 2-RDM method in the same active space requires only 2.1 × 107 variables. Natural orbitals, natural-orbital occupations, charge gaps, and Mulliken charges are reported as a function of polymer length. The polymer, we find, is strongly correlated, despite possessing a simple sp3-hybridized bonding scheme. Calculations reveal the formation of a nearly saturated valence band as the polymer grows and a charge gap that decreases sharply with polymer length.
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Affiliation(s)
- Andrew J S Valentine
- Department of Chemistry and the James Franck Institute, The University of Chicago , Chicago, Illinois 60637, United States
| | - Dmitri V Talapin
- Department of Chemistry and the James Franck Institute, The University of Chicago , Chicago, Illinois 60637, United States
| | - David A Mazziotti
- Department of Chemistry and the James Franck Institute, The University of Chicago , Chicago, Illinois 60637, United States
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Makarov NS, Lim J, Lin Q, Lewellen JW, Moody NA, Robel I, Pietryga JM. Quantum Dot Thin-Films as Rugged, High-Performance Photocathodes. NANO LETTERS 2017; 17:2319-2327. [PMID: 28253617 DOI: 10.1021/acs.nanolett.6b05175] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Typical use of colloidal quantum dots (QDs) as bright, tunable phosphors in real applications relies on engineering of their surfaces to suppress the loss of excited carriers to surface trap states or to the surrounding medium. Here, we explore the utility of QDs in an application that actually exploits their propensity toward photoionization, namely within efficient and robust photocathodes for use in next-generation electron guns. In order to establish the relevance of QD films as photocathodes, we evaluate the efficiency of electron photoemission of films of a variety of compositions in a typical electron gun configuration. By quantifying photocurrent as a function of excitation photon energy, excitation intensity and pulse duration, we establish the role of hot electrons in photoemission within the multiphoton excitation regime. We also demonstrate the effect of QD structure and film deposition methods on efficiency, which suggests numerous pathways for further enhancements. Finally, we show that QD photocathodes offer superior efficiencies relative to standard copper cathodes and are robust against degradation under ambient conditions.
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Affiliation(s)
- Nikolay S Makarov
- Chemistry Division and ‡Accelerator Operations and Technology Division, Los Alamos National Laboratory , Los Alamos, New Mexico 87545, United States
| | - Jaehoon Lim
- Chemistry Division and ‡Accelerator Operations and Technology Division, Los Alamos National Laboratory , Los Alamos, New Mexico 87545, United States
| | - Qianglu Lin
- Chemistry Division and ‡Accelerator Operations and Technology Division, Los Alamos National Laboratory , Los Alamos, New Mexico 87545, United States
| | - John W Lewellen
- Chemistry Division and ‡Accelerator Operations and Technology Division, Los Alamos National Laboratory , Los Alamos, New Mexico 87545, United States
| | - Nathan A Moody
- Chemistry Division and ‡Accelerator Operations and Technology Division, Los Alamos National Laboratory , Los Alamos, New Mexico 87545, United States
| | - István Robel
- Chemistry Division and ‡Accelerator Operations and Technology Division, Los Alamos National Laboratory , Los Alamos, New Mexico 87545, United States
| | - Jeffrey M Pietryga
- Chemistry Division and ‡Accelerator Operations and Technology Division, Los Alamos National Laboratory , Los Alamos, New Mexico 87545, United States
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