Origin of reversible photo-induced phase separation in hybrid perovskites

TL;DR

This study uncovers how local strain from photo-generated polarons causes reversible halide phase separation in hybrid perovskites, affecting device performance and enabling new optoelectronic applications.

Contribution

It combines nanoscale imaging and multiscale modeling to reveal the electromechanical mechanism behind photo-induced phase separation in hybrid perovskites.

Findings

Photo-generated polarons induce local strain promoting phase separation.

Nucleation of iodide-rich clusters is stabilized by light.

Unique electromechanical properties drive the reversible phase behavior.

Abstract

Nonequilibrium processes occurring in functional materials can significantly impact device efficiencies and are often difficult to characterize due to the broad range of length and time scales involved. In particular, mixed halide hybrid perovskites are promising for optoelectronics, yet the halides reversibly phase separate when photo-excited, significantly altering device performance. By combining nanoscale imaging and multiscale modeling, we elucidate the mechanism underlying this phenomenon, demonstrating that local strain induced by photo-generated polarons promotes halide phase separation and leads to nucleation of light-stabilized iodide-rich clusters. This effect relies on the unique electromechanical properties of hybrid materials, characteristic of neither their organic nor inorganic constituents alone. Exploiting photo-induced phase separation and other nonequilibrium phenomena in hybrid materials, generally, could enable new opportunities for expanding the functional applications in sensing, photoswitching, optical memory, and energy storage.