Ultrafast Carrier Dynamics and Terahertz Photoconductivity of Mixed-Cation and Lead Mixed-Halide Hybrid Perovskites**Supported by the National Natural Science Foundation of China under Grant Nos 11604202, 11674213, 61735010 and 51603119, the Young Eastern Scholar under Grant Nos QD2015020 and QD2016027, the Shanghai Rising-Star Program under Grant No 18QA1401700, the ‘Chen Guang’ Project under Grant Nos 16CG45 and 16CG46, the Shanghai Municipal

Abstract

Using time-dependent terahertz spectroscopy, we investigate the role of mixed-cation and mixed-halide on the ultrafast photoconductivity dynamics of two different methylammonium (MA) lead-iodide perovskite thin films. It is found that the dynamics of conductivity after photoexcitation reveals significant correlation on the microscopy crystalline features of the samples. Our results show that mixed-cation and lead mixed-halide affect the charge carrier dynamics of the lead-iodide perovskites. In the (5-AVA)0.05(MA)0.95PbI2.95Cl0.05/spiro thin film, we observe a much weaker saturation trend of the initial photoconductivity with high excitation fluence, which is attributed to the combined effect of sequential charge carrier generation, transfer, cooling and polaron formation.