1
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Wang H, Pinna J, Romero DG, Di Mario L, Koushki RM, Kot M, Portale G, Loi MA. PbS Quantum Dots Ink with Months-Long Shelf-Lifetime Enabling Scalable and Efficient Short-Wavelength Infrared Photodetectors. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2024; 36:e2311526. [PMID: 38327037 DOI: 10.1002/adma.202311526] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2023] [Revised: 01/21/2024] [Indexed: 02/09/2024]
Abstract
The phase-transfer ligand exchange of PbS quantum dots (QDs) has substantially simplified device fabrication giving hope for future industrial exploitation. However, this technique when applied to QDs of large size (>4 nm) gives rise to inks with poor colloidal stability, thus hindering the development of QDs photodetectors in short-wavelength infrared range. Here, it is demonstrated that methylammonium lead iodide ligands can provide sufficient passivation of PbS QDs of size up to 6.7 nm, enabling inks with a minimum of ten-week shelf-life time, as proven by optical absorption and solution-small angle X-ray scattering. Furthermore, the maximum linear electron mobility of 4.7 × 10-2 cm2 V-1 s-1 is measured in field-effect transistors fabricated with fresh inks, while transistors fabricated with the same solution after ten-week storage retain 74% of the average starting electron mobility, demonstrating the outstanding quality both of the fresh and aged inks. Finally, photodetectors fabricated via blade-coating exhibit 76% external quantum efficiency at 1300 nm and 1.8 × 1012 Jones specific detectivity, values comparable with devices fabricated using ink with lower stability and wasteful methods such as spin-coating.
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Affiliation(s)
- Han Wang
- Photophysics and OptoElectronics, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, Groningen, 9747 AG, The Netherlands
| | - Jacopo Pinna
- Photophysics and OptoElectronics, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, Groningen, 9747 AG, The Netherlands
| | - David Garcia Romero
- Photophysics and OptoElectronics, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, Groningen, 9747 AG, The Netherlands
| | - Lorenzo Di Mario
- Photophysics and OptoElectronics, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, Groningen, 9747 AG, The Netherlands
| | - Razieh Mehrabi Koushki
- Photophysics and OptoElectronics, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, Groningen, 9747 AG, The Netherlands
| | - Mordechai Kot
- Photophysics and OptoElectronics, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, Groningen, 9747 AG, The Netherlands
| | - Giuseppe Portale
- Photophysics and OptoElectronics, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, Groningen, 9747 AG, The Netherlands
| | - Maria Antonietta Loi
- Photophysics and OptoElectronics, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, Groningen, 9747 AG, The Netherlands
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2
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Marino E, Rosen DJ, Yang S, Tsai EHR, Murray CB. Temperature-Controlled Reversible Formation and Phase Transformation of 3D Nanocrystal Superlattices Through In Situ Small-Angle X-ray Scattering. NANO LETTERS 2023; 23:4250-4257. [PMID: 37184728 DOI: 10.1021/acs.nanolett.3c00299] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
For decades, the spontaneous organization of nanocrystals into superlattices has captivated the scientific community. However, achieving direct control over the formation of the superlattice and its phase transformations has proven to be a grand challenge, often resulting in the generation of multiple symmetries under the same experimental conditions. Here, we achieve direct control over the formation of the superlattice and its phase transformations by modulating the thermal energy of a nanocrystal dispersion without relying on solvent evaporation. We follow the temperature-dependent dynamics of the self-assembly process using synchrotron-based small-angle X-ray scattering. When cooled below -24.5 °C, lead sulfide nanocrystals form micrometer-sized three-dimensional phase-pure body-centered cubic superlattices. When cooled below -35.1 °C, these superlattices undergo a collective diffusionless phase transformation that yields denser body-centered tetragonal phases. These structural changes can be reversed by increasing the temperature of the dispersion and may lead to the direct modulation of the optical properties of these artificial solids.
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Affiliation(s)
- Emanuele Marino
- Department of Chemistry, University of Pennsylvania, 231 S. 34th Street, Philadelphia, Pennslvania 19104 United States
- Dipartimento di Fisica e Chimica, Università degli Studi di Palermo, Via Archirafi 36, 90123 Palermo, Italy
| | - Daniel J Rosen
- Department of Materials Science and Engineering, University of Pennsylvania, 3231 Walnut Street, Philadelphia, Pennsylvania 19104 United States
| | - Shengsong Yang
- Department of Chemistry, University of Pennsylvania, 231 S. 34th Street, Philadelphia, Pennslvania 19104 United States
| | - Esther H R Tsai
- Center for Functional Nanomaterials, Brookhaven National Laboratory, Building 735, Upton, New York 11973-5000, United States
| | - Christopher B Murray
- Department of Chemistry, University of Pennsylvania, 231 S. 34th Street, Philadelphia, Pennslvania 19104 United States
- Department of Materials Science and Engineering, University of Pennsylvania, 3231 Walnut Street, Philadelphia, Pennsylvania 19104 United States
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3
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Pinna J, Mehrabi Koushki R, Gavhane DS, Ahmadi M, Mutalik S, Zohaib M, Protesescu L, Kooi BJ, Portale G, Loi MA. Approaching Bulk Mobility in PbSe Colloidal Quantum Dots 3D Superlattices. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023; 35:e2207364. [PMID: 36308048 DOI: 10.1002/adma.202207364] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/12/2022] [Revised: 10/13/2022] [Indexed: 06/16/2023]
Abstract
3D superlattices made of colloidal quantum dots are a promising candidate for the next generation of optoelectronic devices as they are expected to exhibit a unique combination of tunable optical properties and coherent electrical transport through minibands. While most of the previous work was performed on 2D arrays, the control over the formation of these systems is lacking, where limited long-range order and energetical disorder have so far hindered the potential of these metamaterials, giving rise to disappointing transport properties. Here, it is reported that nanoscale-level controlled ordering of colloidal quantum dots in 3D and over large areas allows the achievement of outstanding transport properties. The measured electron mobilities are the highest ever reported for a self-assembled solid of fully quantum-confined objects. This ultimately demonstrates that optoelectronic metamaterials with highly tunable optical properties (in this case in the short-wavelength infrared spectral range) and charge mobilities approaching that of bulk semiconductor can be obtained. This finding paves the way toward a new generation of optoelectronic devices.
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Affiliation(s)
- Jacopo Pinna
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh, 4, Groningen, 9747 AG, The Netherlands
| | - Razieh Mehrabi Koushki
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh, 4, Groningen, 9747 AG, The Netherlands
| | - Dnyaneshwar S Gavhane
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh, 4, Groningen, 9747 AG, The Netherlands
| | - Majid Ahmadi
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh, 4, Groningen, 9747 AG, The Netherlands
| | - Suhas Mutalik
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh, 4, Groningen, 9747 AG, The Netherlands
| | - Muhammad Zohaib
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh, 4, Groningen, 9747 AG, The Netherlands
| | - Loredana Protesescu
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh, 4, Groningen, 9747 AG, The Netherlands
| | - Bart J Kooi
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh, 4, Groningen, 9747 AG, The Netherlands
| | - Giuseppe Portale
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh, 4, Groningen, 9747 AG, The Netherlands
| | - Maria Antonietta Loi
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh, 4, Groningen, 9747 AG, The Netherlands
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4
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Study on the Aqueous CdTe Quantum Dots Solar Device Deposited by Blade Coating on Magnesium Zinc Oxide Window Layer. NANOMATERIALS 2022; 12:nano12091523. [PMID: 35564232 PMCID: PMC9099490 DOI: 10.3390/nano12091523] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/11/2022] [Revised: 04/27/2022] [Accepted: 04/28/2022] [Indexed: 12/04/2022]
Abstract
Aqueous CdTe quantum dots solar cells have been successfully fabricated by the blade coating method on the magnesium zinc oxide (Zn1−xMgxO or ZMO) window layer. Compared with the ZMO mono-window layer, the ZMO/CdS bi-window layer can decrease the interface recombination effectively due to the lower lattice mismatch and fast interdiffusion between CdS and CdTe. Moreover, the high temperature annealing of the CdTe quantum dots absorbed layer passivates the grain boundary of the CdTe crystalline via the replacement reaction of tellurium with sulfur. Finally, the conversion efficiency of our aqueous CdTe quantum dots solar device is improved from 3.21% to 8.06% with the introduction of the CdS interlayer and high temperature CdCl2 annealing. Our aqueous CdTe quantum dots solar devices show a large open circuit voltage and fill factor which are comparable with the conventional devices that are fabricated with organic CdTe quantum dots. We believe that it is the spike-like conduction band alignment between the ZMO and CdTe absorbed layer that reduces the majority carrier concentration, leading to the decrease in interface recombination probability.
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5
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Room-Temperature Infrared Photodetectors with Zero-Dimensional and New Two-Dimensional Materials. COATINGS 2022. [DOI: 10.3390/coatings12050609] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Infrared photodetectors have received much attention for several decades due to their broad applications in the military, science, and daily life. However, for achieving an ideal signal-to-noise ratio and a very fast response, cooling is necessary in those devices, which makes them bulky and costly. Thus, room-temperature infrared photodetectors have emerged as a hot research direction. Novel low-dimensional materials with their easy fabrication and excellent photoelectronic properties provide a possible solution for room-temperature infrared photodetectors. This review aims to summarize the preparation methods and characterization of several low-dimensional materials (PbS, PbSe and HgTe, new two-dimensional materials) with great concern and the room-temperature infrared photodetectors based on them.
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6
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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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7
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du Fossé I, Boehme SC, Infante I, Houtepen AJ. Dynamic Formation of Metal-Based Traps in Photoexcited Colloidal Quantum Dots and Their Relevance for Photoluminescence. CHEMISTRY OF MATERIALS : A PUBLICATION OF THE AMERICAN CHEMICAL SOCIETY 2021; 33:3349-3358. [PMID: 34054218 PMCID: PMC8154315 DOI: 10.1021/acs.chemmater.1c00561] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/18/2021] [Revised: 04/09/2021] [Indexed: 05/11/2023]
Abstract
Trap states play a crucial role in the design of colloidal quantum dot (QD)-based technologies. The presence of these in-gap states can either significantly limit the efficiency of devices (e.g., in solar cells or LEDs) or play a pivotal role in the functioning of the technology (e.g., in catalysis). Understanding the atomistic nature of traps is therefore of the highest importance. Although the mechanism through which undercoordinated chalcogenide atoms can lead to trap states in II-VI QDs is generally well understood, the nature of metal-based traps remains more elusive. Previous research has shown that reduction of metal sites in negatively charged QDs can lead to in-gap states. Here, we use density functional theory to show that metal-based traps are also formed in charge-neutral but photoexcited CdSe QDs. It is found that Cd-Cd dimers and the concomitant trap states are transient in nature and appear and disappear on the picosecond time scale. Subsequent nonradiative recombination from the trap is shown to be much faster than radiative recombination, indicating that dimer-related trap states can quench the photoluminescence. These results are expected to be transferable to other II-VI materials and highlight the importance of surface redox reactions for the optical properties of QDs. Moreover, they show that photoexcitation can lead to atomic rearrangements on the surface and thus create transient in-gap states.
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Affiliation(s)
- Indy du Fossé
- Optoelectronic
Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Simon C. Boehme
- Laboratory
of Inorganic Chemistry, Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 1, 8093 Zürich, Switzerland
- Empa-Swiss
Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, 8600 Dübendorf, Switzerland
| | - Ivan Infante
- Department
of Nanochemistry, Istituto Italiano di Tecnologia, Via Morego 30, 16163 Genova, Italy
| | - 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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8
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Sukharevska N, Bederak D, Goossens VM, Momand J, Duim H, Dirin DN, Kovalenko MV, Kooi BJ, Loi MA. Scalable PbS Quantum Dot Solar Cell Production by Blade Coating from Stable Inks. ACS APPLIED MATERIALS & INTERFACES 2021; 13:5195-5207. [PMID: 33470785 PMCID: PMC7863069 DOI: 10.1021/acsami.0c18204] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/10/2020] [Accepted: 01/08/2021] [Indexed: 05/05/2023]
Abstract
The recent development of phase transfer ligand exchange methods for PbS quantum dots (QD) has enhanced the performance of quantum dots solar cells and greatly simplified the complexity of film deposition. However, the dispersions of PbS QDs (inks) used for film fabrication often suffer from colloidal instability, which hinders large-scale solar cell production. In addition, the wasteful spin-coating method is still the main technique for the deposition of QD layer in solar cells. Here, we report a strategy for scalable solar cell fabrication from highly stable PbS QD inks. By dispersing PbS QDs capped with CH3NH3PbI3 in 2,6-difluoropyridine (DFP), we obtained inks that are colloidally stable for more than 3 months. Furthermore, we demonstrated that DFP yields stable dispersions even of large diameter PbS QDs, which are of great practical relevance owing to the extended coverage of the near-infrared region. The optimization of blade-coating deposition of DFP-based inks enabled the fabrication of PbS QD solar cells with power conversion efficiencies of up to 8.7%. It is important to underline that this performance is commensurate with the devices made by spin coating of inks with the same ligands. A good shelf life-time of these inks manifests itself in the comparatively high photovoltaic efficiency of 5.8% obtained with inks stored for more than 120 days.
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Affiliation(s)
- Nataliia Sukharevska
- Zernike
Institute for Advanced Materials, Nijenborgh 4, Groningen 9747 AG, The Netherlands
| | - Dmytro Bederak
- Zernike
Institute for Advanced Materials, Nijenborgh 4, Groningen 9747 AG, The Netherlands
| | - Vincent M. Goossens
- Zernike
Institute for Advanced Materials, Nijenborgh 4, Groningen 9747 AG, The Netherlands
| | - Jamo Momand
- Zernike
Institute for Advanced Materials, Nijenborgh 4, Groningen 9747 AG, The Netherlands
| | - Herman Duim
- Zernike
Institute for Advanced Materials, Nijenborgh 4, Groningen 9747 AG, The Netherlands
| | - Dmitry N. Dirin
- Department
of Chemistry and Applied Biosciences, ETH
Zurich, Vladimir Prelog
Weg 1, Zurich 8093, Switzerland
- EMPA-Swiss
Federal Laboratories for Materials Science and Technology, Uberlandstr. 129, Dubendorf 8600, Switzerland
| | - Maksym V. Kovalenko
- Department
of Chemistry and Applied Biosciences, ETH
Zurich, Vladimir Prelog
Weg 1, Zurich 8093, Switzerland
- EMPA-Swiss
Federal Laboratories for Materials Science and Technology, Uberlandstr. 129, Dubendorf 8600, Switzerland
| | - Bart J. Kooi
- Zernike
Institute for Advanced Materials, Nijenborgh 4, Groningen 9747 AG, The Netherlands
| | - Maria A. Loi
- Zernike
Institute for Advanced Materials, Nijenborgh 4, Groningen 9747 AG, The Netherlands
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9
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Wilhelm M, Kommadath SC, Heimbrodt W. Transfer mechanisms in semiconductor hybrids with colloidal core/shell quantum dots on ZnSe substrates. NANOTECHNOLOGY 2020; 31:505714. [PMID: 32927451 DOI: 10.1088/1361-6528/abb84c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Hybrid systems consisting of colloidal CdS/ZnS core/shell quantum dots on ZnSe semiconductor substrates have been studied by continuous-wave and nanosecond time-resolved photoluminescence. On the basis of kinetic calculations, we studied the interplay between the possible transfer processes in these hybrids. The considered transfer mechanisms were resonance energy transfer, photon reabsorption, electron and hole tunneling. Depending on the size of the CdS cores the dominating transfer mechanism is changing. Carrier tunneling was found only for quantum dots in direct contact to the substrate. For large quantum dots a hole tunneling was found, whereas in case of small dots the fast electron tunneling is decisive. Eventually, we were able to determine the conduction band offset between CdS and ZnSe to 0.56 eV at 10 K.
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Affiliation(s)
- M Wilhelm
- Department of Physics, Philipps-University of Marburg, Renthof 5, D-35032 Marburg, Germany
| | - S C Kommadath
- Department of Physics, Philipps-University of Marburg, Renthof 5, D-35032 Marburg, Germany
| | - W Heimbrodt
- Department of Physics, Philipps-University of Marburg, Renthof 5, D-35032 Marburg, Germany
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10
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Bederak D, Sukharevska N, Kahmann S, Abdu-Aguye M, Duim H, Dirin DN, Kovalenko MV, Portale G, Loi MA. On the Colloidal Stability of PbS Quantum Dots Capped with Methylammonium Lead Iodide Ligands. ACS APPLIED MATERIALS & INTERFACES 2020; 12:52959-52966. [PMID: 33174723 PMCID: PMC7705889 DOI: 10.1021/acsami.0c16646] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Phase-transfer exchange of pristine organic ligands for inorganic ones is essential for the integration of colloidal quantum dots (CQDs) in optoelectronic devices. This method results in a colloidal dispersion (ink) which can be directly deposited by various solution-processable techniques to fabricate conductive films. For PbS CQDs capped with methylammonium lead iodide ligands (MAPbI3), the most commonly employed solvent is butylamine, which enables only a short-term (hours) colloidal stability and thus brings concerns on the possibility of manufacturing CQD devices on a large scale in a reproducible manner. In this work, we studied the stability of alternative inks in two highly polar solvents which impart long-term colloidal stability of CQDs: propylene carbonate (PC) and 2,6-difluoropyridine (DFP). The aging and the loss of the ink's stability were monitored with optical, structural, and transport measurements. With these solvents, PbS CQDs capped with MAPbI3 ligands retain colloidal stability for more than 20 months, both in dilute and concentrated dispersions. After 17 months of ink storage, transistors with a maximum linear mobility for electrons of 8.5 × 10-3 cm2/V s are fabricated; this value is 17% of the one obtained with fresh solutions. Our results show that both PC- and DFP-based PbS CQD inks offer the needed shelf life to allow for the development of a CQD device technology.
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Affiliation(s)
- Dmytro Bederak
- Zernike
Institute for Advanced Materials, University
of Groningen, Nijenborgh
4, Groningen 9747AG, The Netherlands
| | - Nataliia Sukharevska
- Zernike
Institute for Advanced Materials, University
of Groningen, Nijenborgh
4, Groningen 9747AG, The Netherlands
| | - Simon Kahmann
- Zernike
Institute for Advanced Materials, University
of Groningen, Nijenborgh
4, Groningen 9747AG, The Netherlands
| | - Mustapha Abdu-Aguye
- Zernike
Institute for Advanced Materials, University
of Groningen, Nijenborgh
4, Groningen 9747AG, The Netherlands
| | - Herman Duim
- Zernike
Institute for Advanced Materials, University
of Groningen, Nijenborgh
4, Groningen 9747AG, The Netherlands
| | - Dmitry N. Dirin
- Department
of Chemistry and Applied Biosciences, ETH
Zürich, Vladimir
Prelog Weg 1, Zürich 8093, Switzerland
- Empa-Swiss
Federal Laboratories for Materials Science and Technology, Uberlandstrasse 129, Dübendorf 8600, Switzerland
| | - Maksym V. Kovalenko
- Department
of Chemistry and Applied Biosciences, ETH
Zürich, Vladimir
Prelog Weg 1, Zürich 8093, Switzerland
- Empa-Swiss
Federal Laboratories for Materials Science and Technology, Uberlandstrasse 129, Dübendorf 8600, Switzerland
| | - Giuseppe Portale
- Zernike
Institute for Advanced Materials, University
of Groningen, Nijenborgh
4, Groningen 9747AG, The Netherlands
| | - Maria A. Loi
- Zernike
Institute for Advanced Materials, University
of Groningen, Nijenborgh
4, Groningen 9747AG, The Netherlands
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11
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Mai VT, Duong NH, Mai XD. Effect of chloride treatment on optical and electrical properties of PbS quantum dots. Chem Phys 2020. [DOI: 10.1016/j.chemphys.2020.110895] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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12
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Ligand-Length Modification in CsPbBr 3 Perovskite Nanocrystals and Bilayers with PbS Quantum Dots for Improved Photodetection Performance. NANOMATERIALS 2020; 10:nano10071297. [PMID: 32630678 PMCID: PMC7408175 DOI: 10.3390/nano10071297] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/12/2020] [Revised: 06/25/2020] [Accepted: 06/25/2020] [Indexed: 11/21/2022]
Abstract
Nanocrystals surface chemistry engineering offers a direct approach to tune charge carrier dynamics in nanocrystals-based photodetectors. For this purpose, we have investigated the effects of altering the surface chemistry of thin films of CsPbBr3 perovskite nanocrystals produced by the doctor blading technique, via solid state ligand-exchange using 3-mercaptopropionic acid (MPA). The electrical and electro-optical properties of photovoltaic and photoconductor devices were improved after the MPA ligand exchange, mainly because of a mobility increase up to 5 × 10−3cm2/Vs. The same technology was developed to build a tandem photovoltaic device based on a bilayer of PbS quantum dots (QDs) and CsPbBr3 perovskite nanocrystals. Here, the ligand exchange was successfully carried out in a single step after the deposition of these two layers. The photodetector device showed responsivities around 40 and 20 mA/W at visible and near infrared wavelengths, respectively. This strategy can be of interest for future visible-NIR cameras, optical sensors, or receivers in photonic devices for future Internet-of-Things technology.
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13
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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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14
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Sukharevska N, Bederak D, Dirin D, Kovalenko M, Loi MA. Improved Reproducibility of PbS Colloidal Quantum Dots Solar Cells Using Atomic Layer-Deposited TiO 2. ENERGY TECHNOLOGY (WEINHEIM, GERMANY) 2020; 8:1900887. [PMID: 32064223 PMCID: PMC7006825 DOI: 10.1002/ente.201900887] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2019] [Revised: 10/02/2019] [Indexed: 05/16/2023]
Abstract
Thanks to their broadly tunable bandgap and strong absorption, colloidal lead chalcogenide quantum dots (QDs) are highly appealing as solution-processable active layers for third-generation solar cells. However, the modest reproducibility of this kind of solar cell is a pertinent issue, which inhibits the exploitation of this material class in optoelectronics. This issue is not necessarily imputable to the active layer but may originate from different constituents of the device structure. Herein, the deposition of TiO2 electron transport layer is focused on. Atomic layer deposition (ALD) greatly improves the reproducibility of PbS QD solar cells compared with the previously optimized sol-gel (SG) approach. Power conversion efficiency (PCE) of the solar cells using atomic layer-deposited TiO2 lies in the range between 5.5% and 7.2%, whereas solar cells with SG TiO2 have PCE ranging from 0.5% to 6.9% with a large portion of short-circuited devices. Investigations of TiO2 layers by atomic force microscopy and scanning electron microscopy reveal that these films have very different surface morphologies. Whereas the TiO2 films prepared by SG synthesis and deposited by spin coating are very smooth, TiO2 films made by ALD repeat the surface texture of the fluorine-doped tin oxide (FTO) substrate underneath.
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Affiliation(s)
- Nataliia Sukharevska
- Photophysics & OptoElectronicsZernike Institute for Advanced MaterialsNijenborgh 4GroningenAG9747The Netherlands
| | - Dmytro Bederak
- Photophysics & OptoElectronicsZernike Institute for Advanced MaterialsNijenborgh 4GroningenAG9747The Netherlands
| | - Dmitry Dirin
- Department of Chemistry and Applied BiosciencesETH ZurichVladimir Prelog Weg 1Zurich8093Switzerland
| | - Maksym Kovalenko
- Department of Chemistry and Applied BiosciencesETH ZurichVladimir Prelog Weg 1Zurich8093Switzerland
| | - Maria Antonietta Loi
- Photophysics & OptoElectronicsZernike Institute for Advanced MaterialsNijenborgh 4GroningenAG9747The Netherlands
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15
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Abdu-Aguye M, Bederak D, Kahmann S, Killilea N, Sytnyk M, Heiss W, Loi MA. Photophysical and electronic properties of bismuth-perovskite shelled lead sulfide quantum dots. J Chem Phys 2019; 151:214702. [DOI: 10.1063/1.5128885] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Mustapha Abdu-Aguye
- Photophysics and Optoelectronics, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747AG Groningen, The Netherlands
| | - Dmytro Bederak
- Photophysics and Optoelectronics, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747AG Groningen, The Netherlands
| | - Simon Kahmann
- Photophysics and Optoelectronics, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747AG Groningen, The Netherlands
| | - Niall Killilea
- Department of Materials Science and Engineering, Institute of Materials for Electronics and Energy Technology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Energy Campus Nürnberg, 90429 Nürnberg, Germany
| | - Mykhailo Sytnyk
- Department of Materials Science and Engineering, Institute of Materials for Electronics and Energy Technology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Energy Campus Nürnberg, 90429 Nürnberg, Germany
| | - Wolfgang Heiss
- Department of Materials Science and Engineering, Institute of Materials for Electronics and Energy Technology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Energy Campus Nürnberg, 90429 Nürnberg, Germany
| | - Maria Antonietta Loi
- Photophysics and Optoelectronics, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747AG Groningen, The Netherlands
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16
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Abstract
Nanometer-scale crystals of bulk group IV, III-V, II-VI, IV-VI, I-III-VI2, and metal-halide perovskite semiconductors, dispersed in solvents, are known as colloidal nanocrystals and form an excellent, solution-processable materials class for thin film and flexible electronics. This review surveys the size, composition, and surface chemistry-dependent properties of semiconductor NCs and thin films derived therefrom and provides physico-chemical insight into the recent leaps forward in the performance of NC field-effect transistors. Device design and fabrication methods are described that have enabled the demonstration and scaling up in complexity and area and scaling down in device size of flexible, colloidal nanocrystal integrated circuits. Finally, taking stock of the advances made in the science and engineering of NC systems, challenges and opportunities are presented to develop next-generation, colloidal NC electronic materials and devices, important to their potential in future computational and in Internet of Things applications.
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Affiliation(s)
- Cherie R Kagan
- Department of Electrical and Systems Engineering, University of Pennsylvania, 200 South 33rd Street, 364 Levine Hall, Philadelphia, PA 19104, USA.
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17
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Meng L, Zeng T, Jin Y, Xu Q, Wang X. Surface-Modified Substrates for Quantum Dot Inks in Printed Electronics. ACS OMEGA 2019; 4:4161-4168. [PMID: 31459625 PMCID: PMC6648829 DOI: 10.1021/acsomega.9b00195] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2019] [Accepted: 02/13/2019] [Indexed: 05/29/2023]
Abstract
Printed electronics fill the niches for low-cost, flexible devices in electronics. Developing substrates suitable for various printable electronic inks becomes an important topic in both academia and industry. Because of their extraordinary properties like solution processability, colloidal quantum dots (QDs) are gradually emerging in this field as promising candidates for electronic inks. In recent years, researchers have successfully produced high quality PbS QD inks in polar solvents. However, the incorporation of electronic inks onto a well-passivated substrate remains challenging due to the processing incompatibility between polar solvents and hydrophobic substrates. Here, we propose a surface modification strategy by using chlorine to achieve both trap-site suppression and a hydrophilic surface. The chlorine can effectively passivate the surface dangling bonds and charged hydroxyls while creating a hydrophilic surface. On this modified substrate, the contact angle between the water droplet and the SiO2 substrate can be as small as 20° and this strategy is also feasible for other polymer and inorganic substrates. For a proof-of-concept demonstration, we fabricated a PbS QD ink-based field-effect transistor on a Cl-passivated substrate, and the device showed a mobility as high as 4.36 × 10-3 cm2/V s, which indicates effective trap-site suppression. This device also enables the potential of the Cl-passivated substrates for QD inks with water or other polar solvents.
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Affiliation(s)
- Lingju Meng
- Department
of Electrical and Computer Engineering, University of Alberta, 9107-116 Street, Edmonton, Canada T6G 2V4
| | - Tao Zeng
- Department
of Electrical and Computer Engineering, University of Alberta, 9107-116 Street, Edmonton, Canada T6G 2V4
- School
of Material Science and Engineering, Jingdezhen
Ceramic Institute (Xianghu Campus), Xianghu Road, Jingdezhen 333000, Jiangxi, P.
R. China
| | - Yihan Jin
- Department
of Electrical and Computer Engineering, University of Alberta, 9107-116 Street, Edmonton, Canada T6G 2V4
- School
of Optoelectronics, Beijing Institute of
Technology, No. 5 South Zhong Guan Cun Street, Beijing 100081, P. R. China
| | - Qiwei Xu
- Department
of Electrical and Computer Engineering, University of Alberta, 9107-116 Street, Edmonton, Canada T6G 2V4
| | - Xihua Wang
- Department
of Electrical and Computer Engineering, University of Alberta, 9107-116 Street, Edmonton, Canada T6G 2V4
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18
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YousefiAmin A, Killilea NA, Sytnyk M, Maisch P, Tam KC, Egelhaaf HJ, Langner S, Stubhan T, Brabec CJ, Rejek T, Halik M, Poulsen K, Niehaus J, Köck A, Heiss W. Fully Printed Infrared Photodetectors from PbS Nanocrystals with Perovskite Ligands. ACS NANO 2019; 13:2389-2397. [PMID: 30706709 DOI: 10.1021/acsnano.8b09223] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Colloidal nanocrystals from PbS are successfully applied in highly sensitive infrared photodetectors with various device architectures. Here, we demonstrate all-printed devices with high detectivity (∼1012 cm Hz1/2/W) and a cut-off frequency of >3 kHz. The low material consumption (<0.3 mg per detector) and short processing time (14 s per detector) enabled by the automated printing promises extremely low device costs. To enable all-printed devices, an ink formulation was developed based on nanocrystals stabilized by perovskite-like methylammonium iodobismuthate ligands, which are dispersed in a ternary solvent. Fully inkjet printed devices based on this solvent were achieved with printed silver electrodes and a ZnO interlayer. Considerable improvements were obtained by the addition of small amounts of the polymer poly(vinylpyrrolidone) to the ink. The polymer improved the colloidal stability of the ink and its film-formation properties and thus enabled the scalable printing of single detectors and detector arrays. While photoconductors were shown here, the developed ink will certainly find application in a series of further electronic devices based on nanocrystals from a broad range of materials.
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Affiliation(s)
- AmirAbbas YousefiAmin
- Institute - Materials for Electronics and Energy Technology, Department of Materials Science and Engineering , Friedrich-Alexander-Universität Erlangen-Nürnberg, Energy Campus Nürnberg , Fürtherstraße 250 , D-90429 Nürnberg , Germany
| | - Niall A Killilea
- Institute - Materials for Electronics and Energy Technology, Department of Materials Science and Engineering , Friedrich-Alexander-Universität Erlangen-Nürnberg, Energy Campus Nürnberg , Fürtherstraße 250 , D-90429 Nürnberg , Germany
| | - Mykhailo Sytnyk
- Institute - Materials for Electronics and Energy Technology, Department of Materials Science and Engineering , Friedrich-Alexander-Universität Erlangen-Nürnberg, Energy Campus Nürnberg , Fürtherstraße 250 , D-90429 Nürnberg , Germany
| | - Philipp Maisch
- Institute - Materials for Electronics and Energy Technology, Department of Materials Science and Engineering , Friedrich-Alexander-Universität Erlangen-Nürnberg , Martensstraße 7 , D-91058 Erlangen , Germany
| | - Ka Cheong Tam
- Bavarian Center for Applied Energy Research (ZAE Bayern), Energy Campus Nürnberg , Fürther Straße 250 , D-90429 Nürnberg , Erlangen Germany
| | - Hans-Joachim Egelhaaf
- Bavarian Center for Applied Energy Research (ZAE Bayern), Energy Campus Nürnberg , Fürther Straße 250 , D-90429 Nürnberg , Erlangen Germany
| | - Stefan Langner
- Institute - Materials for Electronics and Energy Technology, Department of Materials Science and Engineering , Friedrich-Alexander-Universität Erlangen-Nürnberg , Martensstraße 7 , D-91058 Erlangen , Germany
| | - Tobias Stubhan
- Bavarian Center for Applied Energy Research (ZAE Bayern), Energy Campus Nürnberg , Fürther Straße 250 , D-90429 Nürnberg , Erlangen Germany
| | - Christoph J Brabec
- Institute - Materials for Electronics and Energy Technology, Department of Materials Science and Engineering , Friedrich-Alexander-Universität Erlangen-Nürnberg , Martensstraße 7 , D-91058 Erlangen , Germany
| | - Tobias Rejek
- Institute of Polymer Materials, Department of Materials Science and Engineering , Friedrich-Alexander-University Erlangen-Nürnberg , Martensstrasse 7 , D-91058 Erlangen , Germany
| | - Marcus Halik
- Institute of Polymer Materials, Department of Materials Science and Engineering , Friedrich-Alexander-University Erlangen-Nürnberg , Martensstrasse 7 , D-91058 Erlangen , Germany
| | - Katharina Poulsen
- Centrum für Angewandte Nanotechnologie (CAN) GmbH i. L. , Grindelallee 117 , D-20146 Hamburg , Germany
| | - Jan Niehaus
- Centrum für Angewandte Nanotechnologie (CAN) GmbH i. L. , Grindelallee 117 , D-20146 Hamburg , Germany
| | - Anton Köck
- Materials Center Leoben Forschung GmbH , Roseggerstraße 12 , A-8700 Leoben , Austria
| | - Wolfgang Heiss
- Institute - Materials for Electronics and Energy Technology, Department of Materials Science and Engineering , Friedrich-Alexander-Universität Erlangen-Nürnberg, Energy Campus Nürnberg , Fürtherstraße 250 , D-90429 Nürnberg , Germany
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19
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Beygi H, Sajjadi SA, Babakhani A, Young JF, van Veggel FCJM. Halide-, Hybrid-, and Perovskite-Functionalized Light Absorbing Quantum Materials of p-i-n Heterojunction Solar Cells. ACS APPLIED MATERIALS & INTERFACES 2018; 10:30283-30295. [PMID: 30107115 DOI: 10.1021/acsami.8b06967] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The p-i-n quantum dot (QD) solar cells were fabricated through the single-step deposition of both of its p-type and light absorbing quantum layers. The hole transport and light absorbing layers of these devices were made by the p- and n-type PbS QDs, which were functionalized with mercaptopropionic acid and different halide, hybrid, and perovskite ligands, respectively. Fabrication of such p-i-n devices by the single-step deposition of pre-exchanged colloidal QDs had not been fully investigated so far because of the low progression of ligand exchange processes, weak colloidal stability of pre-exchanged QDs in desired solvents, and remaining of the ligand exchange products along with particles. However, we showed that the type of ligand complexes, amino acid products of ligand exchange, and protic solvents are highly effective for increasing the ligand exchange progression and preparation of high colloidal stability QDs with superior photoluminescence properties. As well, the surface chemistry investigations by the means of Fourier transform infrared, nuclear magnetic resonance, X-ray photoelectron spectroscopy, X-ray diffraction, inductively coupled plasma optical emission spectrometry, carbon-hydrogen-nitrogen-sulfur elemental analysis, zeta potential, and high-resolution transmission electron microscopy were led to the presentation of new concepts about the theoretical and experimental ligand weight percentages, the mechanisms of solution-phase ligand exchange processes, and formation of ligands adlayer on the (111) facets of QDs. The pre-exchanged colloidal QDs showed very good desirability for the single-step deposition of dense, defects-free, and smooth QD layers. Regarding that, the p-i-n solar cells were successfully fabricated by the single-step deposition of both of the QD layers. Especially, the highest power conversion efficiency value of 6.40% was recorded for the devices in which the light absorbing layer was prepared by the composite-like QD-perovskite structures.
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Affiliation(s)
- Hossein Beygi
- Department of Materials Science and Metallurgical Engineering, Engineering Faculty , Ferdowsi University of Mashhad , Mashhad 91775-1111 , Iran
- Department of Physics and Astronomy , University of British Columbia , Vancouver V6T 1Z1 , British Columbia , Canada
| | - Seyed Abdolkarim Sajjadi
- Department of Materials Science and Metallurgical Engineering, Engineering Faculty , Ferdowsi University of Mashhad , Mashhad 91775-1111 , Iran
| | - Abolfazl Babakhani
- Department of Materials Science and Metallurgical Engineering, Engineering Faculty , Ferdowsi University of Mashhad , Mashhad 91775-1111 , Iran
| | - Jeff F Young
- Department of Physics and Astronomy , University of British Columbia , Vancouver V6T 1Z1 , British Columbia , Canada
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20
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Charge Transport in Trap-Sensitized Infrared PbS Quantum-Dot-Based Photoconductors: Pros and Cons. NANOMATERIALS 2018; 8:nano8090677. [PMID: 30200230 PMCID: PMC6165075 DOI: 10.3390/nano8090677] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/02/2018] [Revised: 08/23/2018] [Accepted: 08/28/2018] [Indexed: 12/15/2022]
Abstract
Control of quantum-dot (QD) surface chemistry offers a direct approach for the tuning of charge-carrier dynamics in photoconductors based on strongly coupled QD solids. We investigate the effects of altering the surface chemistry of PbS QDs in such QD solids via ligand exchange using 3-mercaptopropionic acid (MPA) and tetrabutylammonium iodide (TBAI). The roll-to-roll compatible doctor-blade technique was used for the fabrication of the QD solid films as the photoactive component in photoconductors and field-effect phototransistors. The ligand exchange of the QD solid film with MPA yields superior device performance with higher photosensitivity and detectivity, which is due to less dark current and lower noise level as compared to ligand exchange with TBAI. In both cases, the mechanism responsible for photoconductivity is related to trap sensitization of the QD solid, in which traps are responsible of high photoconductive gain values, but slow response times under very low incident optical power (<1 pW). At medium⁻high incident optical powers (>100 pW), where traps are filled, both MPA- and TBAI-treated photodevices exhibit similar behavior, characterized by lower responsivity and faster response time, as limited by the mobility in the QD solid.
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