Thongnum Anusit, Pinsook Udomsilp
Department of Physics, Faculty of Science, Srinakharinwirot University, Bangkok 10110, Thailand.
Thailand Center of Excellence in Physics, Commission on Higher Education, Bangkok 10400, Thailand and Department of Physics, Faculty of Science, Chulalongkorn University, Bangkok 10300, Thailand.
Nanoscale. 2020 Jul 9;12(26):14112-14119. doi: 10.1039/d0nr03432k.
A comprehensive study of the transport properties of a prototypical CH3NH3PbI3 thin film is presented. The polaron-longitudinal optical (LO) phonon scattering mechanism, based on Low-Pines's polaron mobility, was studied to elucidate the charge-carrier mobility. We found that the calculated mobilities showed very good quantitative agreement with the experimental data measured in thin film samples using photoconductivity techniques. In THz mobility, the calculated results yielded room-temperature (RT) mobilities of ∼650 cm2 V-1 s-1 (single crystal) and ∼220 cm2 V-1 s-1 (disordered thin film) at a low quantum yield (φ) and 32 cm2 V-1 s-1 (high-quality thin film) at φ = 1. The dynamic disorder due to organic reorientation was included in the calculations. Its effect provided a power law mobility of μ ∝ Tm and satisfactorily supported temperature-dependent mobility over the temperature range of 80-370 K. In the orthorhombic and tetragonal phases, the charge-carrier mobilities with dynamic disorder were approximately 47% and 22% lower than those obtained from phases without dynamic disorder. The RT mobility was 26 cm2 V-1 s-1 at φ = 1. In the low-temperature orthorhombic phase, the structural phase transition was considered. The mobility followed a power law with m = -1.7. In the tetragonal and cubic phases, the mobility also followed a power law, but with m = -1.1, which is an intermediate range in optical phonon scattering. When combined with recent theoretical analysis, we also found three limitations of power law mobility with exponents between -0.46 and -1.1 for polaron-LO phonon scattering, -1.2 and -1.6 for bare carrier-LO phonon scattering, and -1.7 and -2.0 for carrier scattering off optical phonons and lattice fluctuations. This work not only provides a description of temperature-dependent mobility in CH3NH3PbI3 thin films, but also gives new insights into THz photoconductivity and the relationship between LO phonon scattering and power law mobility.
本文对典型的CH3NH3PbI3薄膜的输运性质进行了全面研究。基于Low-Pines极化子迁移率，研究了极化子-纵向光学（LO）声子散射机制，以阐明电荷载流子迁移率。我们发现，计算得到的迁移率与使用光电导技术在薄膜样品中测量的实验数据在定量上吻合得非常好。在太赫兹迁移率方面，计算结果表明，在低量子产率（φ）下，室温（RT）迁移率为650 cm2 V-1 s-1（单晶）和220 cm2 V-1 s-1（无序薄膜），在φ = 1时为32 cm2 V-1 s-1（高质量薄膜）。计算中考虑了由于有机重排引起的动态无序。其效应给出了幂律迁移率μ ∝ Tm，并在80 - 370 K的温度范围内令人满意地支持了与温度相关的迁移率。在正交相和四方相中，考虑动态无序时的电荷载流子迁移率比不考虑动态无序时的相分别低约47%和22%。在φ = 1时，室温迁移率为26 cm2 V-1 s-1。在低温正交相中，考虑了结构相变。迁移率遵循幂律，m = -1.7。在四方相和立方相中，迁移率也遵循幂律，但m = -1.1，这是光学声子散射的中间范围。结合最近的理论分析，我们还发现了极化子-LO声子散射幂律迁移率指数在-0.46和-1.1之间、裸载流子-LO声子散射幂律迁移率指数在-1.2和-1.6之间以及载流子与光学声子和晶格涨落散射幂律迁移率指数在-1.7和-2.0之间的三个局限性。这项工作不仅描述了CH3NH3PbI3薄膜中与温度相关的迁移率，还为太赫兹光电导以及LO声子散射与幂律迁移率之间的关系提供了新的见解。
