Light-induced Suppression on Forming Secondary Phases in FA-rich Perovskite

Abstract

Investigating the environmental factors that affect the degradation pathway in hybrid organic-inorganic perovskites such as (MA,FA,Cs)Pb(I,Br)3 is important for improving their stability. In this work, we show that illumination with above bandgap stabilizes FA-rich perovskites films. Bright-field and dark-field microscopy images were collected in-situ during the degradation and showed that FA-rich perovskites aged under illumination formed less secondary phases than control samples aged in the dark. These secondary phases were confirmed to be intermediate products of degradation by X-ray diffraction. The light-induced stabilization in perovskites films are only observed in FA-rich perovskites. We investigated the effect on perovskites structure resulted from alloying different cations in the films using Williamson-Hall analysis and the impact on light absorption by analyzing the below bandgap absorption states (Urbach tails). Therefore, this work demonstrates the phenomenon of light slowed down the formation of intermediate degradation products, and resulted in more stable perovskite structure.