A Direct Mapping Approach to Understand Carrier Relaxation Dynamics in Varied Regions of a Polycrystalline Perovskite Film

Amir Fathi; Efat Jokar; Yuan-Pern Lee; Eric Wei-Guang Diau

doi:10.1002/anie.202008305

A Direct Mapping Approach to Understand Carrier Relaxation Dynamics in Varied Regions of a Polycrystalline Perovskite Film

Angew Chem Int Ed Engl. 2020 Oct 19;59(43):19001-19005. doi: 10.1002/anie.202008305. Epub 2020 Aug 26.

Authors

Amir Fathi¹, Efat Jokar², Yuan-Pern Lee^{1

2}, Eric Wei-Guang Diau^{1

2}

Affiliations

¹ Department of Applied Chemistry and Institute of Molecular Science, National Chiao Tung University, 1001 Ta-Hsueh Rd., Hsinchu, 30010, Taiwan.
² Center for Emergent Functional Matter Science, National Chiao Tung University, 1001 Ta-Hsueh Rd., Hsinchu, 30010, Taiwan.

PMID: 32681616
DOI: 10.1002/anie.202008305

Abstract

We developed a direct mapping approach to overlay the image of a polycrystalline perovskite film obtained from the transient absorption microscope (TAM) with that from the scanning electron microscope (SEM). By mapping these imaging data pixel by pixel, we are able to observe the relaxation dynamics of the photo-generated charge carriers on varied regions of the film. The carrier relaxation dynamics contain a dominated single-exponential decay component owing to the recombination of charge carriers. The lifetime distribution of charge recombination shows a bimodal feature, for which the rapid and slow distributions are assigned as free and trapped carriers, respectively. The charge recombination was slower in the grain boundary (GB) region than in the grain interior (GI) region. The small grains have longer lifetimes than the large grains for the crystal size smaller than 500 nm. Therefore, GB with retarded charge recombination might play a positive role in a perovskite solar cell.

Keywords: image processing; lifetime mapping; organo-inorganic halide perovskites; transient absorption microscopy; ultrafast imaging.