Browsing by Author "Shrestha, Shreetu"

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    In-situ observation of trapped carriers in organic metal halide perovskite films with ultra-fast temporal and ultra-high energetic resolutions
    (Nature Portfolio, 2021) Kobbekaduwa, Kanishka; Shrestha, Shreetu; Adhikari, Pan; Liu, Exian; Coleman, Lawrence; Zhang, Jianbing; Shi, Ying; Zhou, Yuanyuan; Bekenstein, Yehonadav; Yan, Feng; Rao, Apparao M.; Tsai, Hsinhan; Beard, Matthew C.; Nie, Wanyi; Gao, Jianbo; Clemson University; United States Department of Energy (DOE); Los Alamos National Laboratory; Huazhong University of Science & Technology; Jilin University; Hong Kong Baptist University; Technion Israel Institute of Technology; University of Alabama Tuscaloosa; National Renewable Energy Laboratory - USA
    We in-situ observe the ultrafast dynamics of trapped carriers in organic methyl ammonium lead halide perovskite thin films by ultrafast photocurrent spectroscopy with a sub-25 picosecond time resolution. Upon ultrafast laser excitation, trapped carriers follow a phonon assisted tunneling mechanism and a hopping transport mechanism along ultra-shallow to shallow trap states ranging from 1.72-11.51 millielectronvolts and is demonstrated by time-dependent and independent activation energies. Using temperature as an energetic ruler, we map trap states with ultra-high energy resolution down to < 0.01 millielectronvolt. In addition to carrier mobility of similar to 4 cm(2)V(-1)s(-1) and lifetime of similar to 1 nanosecond, we validate the above transport mechanisms by highlighting trap state dynamics, including trapping rates, de-trapping rates and trap properties, such as trap density, trap levels, and capture-cross sections. In this work we establish a foundation for trap dynamics in high defect-tolerant perovskites with ultra-fast temporal and ultra-high energetic resolution.