Effect of Halide Composition on the Photochemical Stability of Perovskite Photovoltaic Materials

TL;DR

This study investigates how halide composition affects the photochemical stability of mixed halide perovskite films under accelerated sunlight, revealing bromine's role in accelerating degradation and comparing results to outdoor conditions.

Contribution

It provides new insights into the stability of mixed halide perovskites and the impact of bromine content on their degradation under simulated sunlight.

Findings

MAPbBr3 shows no degradation under testing.

Bromine accelerates perovskite degradation.

Accelerated testing correlates with outdoor sunlight exposure.

Abstract

Photochemical stability of encapsulated films of mixed halide perovskites with a range of MAPb(I1-xBrx)3 compositions (solid solutions) was investigated under accelerated stressing using concentrated sunlight. Evolution of light absorption and the corresponding structural modifications in the films were recorded by UV-vis spectroscopy and X-ray diffraction (XRD), respectively. MAPbBr3 film exhibited no degradation. In MAPbI3 and mixed halide MAPb(I1-xBrx)3 films, decomposition of the perovskite material with crystallization of inorganic PbI2, and the corresponding degradation of light absorption, were recorded. Introduction of bromine into the solid solution was found to stress its structure and accelerate the degradation. The relevance of accelerated testing to standard operational conditions of solar cells was confirmed by comparison to degradation experiments under outdoor sunlight exposure. Reasons for the reduced stability of the mixed halide compositions are discussed.