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Ibrahem MA, Waris M, Miah MR, Shabani F, Canimkurbey B, Unal E, Delikanli S, Demir HV. Orientation-Dependent Photoconductivity of Quasi-2D Nanocrystal Self-Assemblies: Face-Down, Edge-Up Versus Randomly Oriented Quantum Wells. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2024; 20:e2401423. [PMID: 38770984 DOI: 10.1002/smll.202401423] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/22/2024] [Revised: 04/30/2024] [Indexed: 05/22/2024]
Abstract
Here, strongly orientation-dependent lateral photoconductivity of a CdSe monolayer colloidal quantum wells (CQWs) possessing short-chain ligands is reported. A controlled liquid-air self-assembly technique is utilized to deliberately engineer the alignments of CQWs into either face-down (FO) or edge-up (EO) orientation on the substrate as opposed to randomly oriented (RO) CQWs prepared by spin-coating. Adapting planar configuration metal-semiconductor-metal (MSM) photodetectors, it is found that lateral conductivity spans ≈2 orders of magnitude depending on the orientation of CQWs in the film in the case of utilizing short ligands. The long native ligands of oleic acid (OA) are exchanged with short-chain ligands of 2-ethylhexane-1-thiol (EHT) to reduce the inter-platelet distance, which significantly improved the photoresponsivity from 4.16, 0.58, and 4.79 mA W-1 to 528.7, 6.17, and 94.2 mA W-1, for the MSM devices prepared with RO, FO, and EO, before and after ligands exchange, respectively. Such CQW orientation control profoundly impacts the photodetector performance also in terms of the detection speed (0.061 s/0.074 s for the FO, 0.048 s/0.060 s for the EO compared to 0.10 s/0.16 s for the RO, for the rise and decay time constants, respectively) and the detectivity (1.7 × 1010, 2.3 × 1011, and 7.5 × 1011 Jones for the FO, EO, and RO devices, respectively) which can be further tailored for the desired optoelectronic device applications. Attributed to charge transportation in colloidal films being proportional to the number of hopping steps, these findings indicate that the solution-processed orientation of CQWs provides the ability to tune the photoconductivity of CQWs with short ligands as another degree of freedom to exploit and engineer their absorptive devices.
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Affiliation(s)
- Mohammed A Ibrahem
- Department of Electrical and Electronics Engineering, Department of Physics, UNAM - Institute of Materials Science and Nanotechnology and The National Nanotechnology Research Center, Bilkent University, Ankara, 06800, Turkey
- Laser Science and Technology Branch, Applied Sciences Department, University of Technology, Baghdad, 10066, Iraq
| | - Mohsin Waris
- Department of Electrical and Electronics Engineering, Department of Physics, UNAM - Institute of Materials Science and Nanotechnology and The National Nanotechnology Research Center, Bilkent University, Ankara, 06800, Turkey
| | - Md Rumon Miah
- Department of Electrical and Electronics Engineering, Department of Physics, UNAM - Institute of Materials Science and Nanotechnology and The National Nanotechnology Research Center, Bilkent University, Ankara, 06800, Turkey
| | - Farzan Shabani
- Department of Electrical and Electronics Engineering, Department of Physics, UNAM - Institute of Materials Science and Nanotechnology and The National Nanotechnology Research Center, Bilkent University, Ankara, 06800, Turkey
| | - Betul Canimkurbey
- Department of Electrical and Electronics Engineering, Department of Physics, UNAM - Institute of Materials Science and Nanotechnology and The National Nanotechnology Research Center, Bilkent University, Ankara, 06800, Turkey
- Serefeddin Health Services Vocational School, Central Research Laboratory, Amasya University, Amasya, 05100, Turkey
| | - Emre Unal
- Department of Electrical and Electronics Engineering, Department of Physics, UNAM - Institute of Materials Science and Nanotechnology and The National Nanotechnology Research Center, Bilkent University, Ankara, 06800, Turkey
| | - Savas Delikanli
- Department of Electrical and Electronics Engineering, Department of Physics, UNAM - Institute of Materials Science and Nanotechnology and The National Nanotechnology Research Center, Bilkent University, Ankara, 06800, Turkey
| | - Hilmi Volkan Demir
- Department of Electrical and Electronics Engineering, Department of Physics, UNAM - Institute of Materials Science and Nanotechnology and The National Nanotechnology Research Center, Bilkent University, Ankara, 06800, Turkey
- Luminous! Center of Excellence for Semiconductor Lighting and Displays, School of Electrical and Electronic Engineering, Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, School of Materials Science and Engineering, Nanyang Technological University, Singapore, 639798, Singapore
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Li C, Hsu SC, Lin JX, Chen JY, Chuang KC, Chang YP, Hsu HS, Chen CH, Lin TS, Liu YH. Giant Zeeman Splitting for Monolayer Nanosheets at Room Temperature. J Am Chem Soc 2020; 142:20616-20623. [PMID: 33249824 DOI: 10.1021/jacs.0c05368] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Giant Zeeman splitting and zero-field splitting (ZFS) are observed in 2D nanosheets that have monolayers of atomic thickness. In this study, single-crystalline CdSe(ethylenediamine)0.5 and Mn2+-doped nanosheets are synthesized via a solvothermal process. Tunable amounts of Mn2+(0.5-8.0%) are introduced, resulting in lattice contraction as well as phosphorescence from five unpaired electrons. The exciton dynamics are dominated by spin-related electronic transitions (4T1 → 6A1) with long lifetimes (20.5, 132, and 295 μs). Temperature-varied EPR spectroscopy with spectral simulation reveals large ZFS (D = 3850 MHz) due to axial distortion of substituted Mn2+ (S = 5/2). In the magnetic circular dichroism (MCD) measurements, we observed giant Zeeman splitting with large effective g values (up to 231 ± 21), which implies huge sp-d exchange interactions in 2D monolayer regimes, leading to diluted magnetic semiconductor (DMS) materials.
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Affiliation(s)
- Chi Li
- Department of Chemistry, National Taiwan Normal University, Taipei 11677, Taiwan, ROC
| | - Sheng-Chih Hsu
- Department of Chemistry, National Taiwan Normal University, Taipei 11677, Taiwan, ROC
| | - Jun-Xiao Lin
- Department of Applied Physics, National Pingtung University, Pingtung 90003, Taiwan, ROC
| | - Jou-Yun Chen
- Department of Chemistry, National Sun Yat-Sen University, Kaohsiung 80424, Taiwan, ROC
| | - Kai-Chun Chuang
- Department of Chemistry, National Taiwan Normal University, Taipei 11677, Taiwan, ROC
| | - Yuan-Pin Chang
- Department of Chemistry, National Sun Yat-Sen University, Kaohsiung 80424, Taiwan, ROC
| | - Hua-Shu Hsu
- Department of Applied Physics, National Pingtung University, Pingtung 90003, Taiwan, ROC
| | - Ching-Hsiang Chen
- Graduate Institute of Applied Science and Technology, National Taiwan University of Science & Technology, Taipei 10673, Taiwan, ROC
| | - Tien-Sung Lin
- Department of Chemistry, Washington University, Saint Louis, Missouri 63130, United States
| | - Yi-Hsin Liu
- Department of Chemistry, National Taiwan Normal University, Taipei 11677, Taiwan, ROC
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