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Photocurrent Imaging of Single-Crystal Methylammonium Lead Iodide Nanostructures
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| 자료유형 | 학위논문 |
|---|---|
| 서명/저자사항 | Photocurrent Imaging of Single-Crystal Methylammonium Lead Iodide Nanostructures. |
| 개인저자 | Xiao, Rui. |
| 단체저자명 | University of California, Davis. Physics. |
| 발행사항 | [S.l.]: University of California, Davis., 2019. |
| 발행사항 | Ann Arbor: ProQuest Dissertations & Theses, 2019. |
| 형태사항 | 90 p. |
| 기본자료 저록 | Dissertations Abstracts International 81-04B. Dissertation Abstract International |
| ISBN | 9781085795531 |
| 학위논문주기 | Thesis (Ph.D.)--University of California, Davis, 2019. |
| 일반주기 |
Source: Dissertations Abstracts International, Volume: 81-04, Section: B.
Advisor: Yu, Dong. |
| 이용제한사항 | This item must not be sold to any third party vendors. |
| 요약 | Hybrid organic-inorganic metal halide perovskite, as exemplified by methylammonium lead iodide (CH3NH3PbI3 or MAPbI3), have demonstrated great potentials for cost-effective solar energy conversion. In this dissertation, a comprehensive investigation of synthesis and optoelectronic properties of MAPbI3 single crystal nanowires/nanoplates was performed. In particular, photocurrent imaging, where photocurrent is mapped as a function of local photoexcitation position, has been used to provide key insights in understanding transport of photogenerated charge carrier at both room temperature and low temperature. The interpretation of photocurrent imaging experimental results is further confirmed, such as the extraction of carrier diffusion length, by comprehensive finite element simulation.Field effect transistor (FET) devices are fabricated by directly transferring the solution-grown nanowires/nanoplates onto the pre-patterned electrodes. Transport measurements indicate the nanostructures make Schottky junctions to the electrodes, forming a back-to-back diode geometry, which is further evidenced by the surface potential measurements with the Kelvin probe force microscopy (KPFM). The scanning photocurrent microscopy (SPCM) measurements reveal a minority carrier diffusion length up to 21 關m at room temperature, much longer than the values observed in polycrystalline thin films. This research not only sets a new benchmark for the carrier diffusion length in MAPbI3 perovskite nanostructures, but also provides new insights to the carrier transport and dynamics.The temperature dependent transport measurements exhibit a sharp change in the electronic properties at around 160 K, in agreement with the temperature of the tetragonal-to-orthorhombic phase transition reported in the literature. The temperature dependent SPCM measurements reveal a drastic increase in carrier diffusion length below 160 K. The over 100 關m long minority carrier diffusion length at 80 K suggests an extremely high carrier mobility up to 104 cm2/Vs as estimated from the free carrier model. The remarkably high mobility, in turn, suggests an excitonic nature of the carrier transport dynamics at low temperature, while a better understanding requires more accurate measurements on carrier lifetime in future work.As a complementary study, a two-dimensional (2D) cross-sectional modeling of thin-film FETs under local photoexcitation is performed with COMSOL Multiphysics. The simulation results validate that accurate minority carrier diffusion lengths can be extracted from SPCM measurements regardless of the substantial nonuniformity in carrier density and potential. However, at high excitation intensity, the photocurrent decay lengths deviate from the minority carrier diffusion lengths as a result of light-induced carrier drift. This work provides confirmation and guidance for interpreting SPCM results and employing photocurrent imaging to determine important charge transport characteristics of gated thin-film and nanowire devices. |
| 일반주제명 | Condensed matter physics. Nanotechnology. Alternative energy. |
| 언어 | 영어 |
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