Effect of alloying on the carrier dynamics in high-performance perovskite solar cells

High-efficiency solar cells often require light absorbers prepared from alloys, such as CdTe1-xSex, CuInxGa1-xSe2, Cu2ZnSnS4-xSex, and (Cs(x)FA(1-x))Pb(I(1-y)Bry)(3). However, how alloying affects solar cell performance is poorly understood, and determining common features associated with alloying is of significant interest. Herein, we studied the correlation between the A/X site compositional ratio and the photo-generated carrier dynamics using mixed halide perovskites (Cs(x)FA(1-x))Pb(IyBr1-y)(3) as examples. Nonadiabatic molecular dynamics calculations demonstrated that charge carrier recombination is highly sensitive to the compositional ratio at the A/X-site. The enhanced lifetime is attributable to the suppression of atomic fluctuations, the weakening of electron-phonon coupling, and a reduction in the electron-transition probability between band edges. The optimal Br concentration was determined to be-18%, in agreement with experimental observations. This study not only advances our understanding of why mixed perovskites usually exhibit superior experimental photoelectric properties, but also provides a route for optimizing the carrier lifetimes and efficiencies of perovskite solar cells. (c) 2021 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by ELSEVIER B.V. and Science Press. All rights reserved.

Automated summary

This study investigates the correlation between the compositional ratio of the A/X site and the photo-generated carrier dynamics in mixed halide perovskites. The results demonstrate that alloying significantly influences the performance of solar cells by suppressing atomic fluctuations, weakening electron-phonon coupling, and reducing electron-transition probability. The findings provide insights into the optimization of carrier lifetimes and efficiencies in perovskite solar cells.