Mixed Halide Perovskite Solar Cells. Consequence of Iodide Treatment on Phase Segregation Recovery

Photoinduced halide ion segregation in mixed halide perovskites can introduce a detrimental effect on the photovoltaic performance of perovskite solar cells over extended light exposure. The photoconversion efficiency decreases from 5.5 to 2.3% when methylammonium lead mixed halide perovskite (MAPbBr1.5I1.5) solar cells are exposed to 25 min of continuous illumination with visible light. The formation of iodide-rich and bromide rich-regions creates traps, which serve as bottlenecks to the flow of charge carriers. Iodide treatment overcomes some of these effects and stabilizes the solar cell performance. It also facilitates quicker recovery in the dark. The decrease in open-circuit voltage following the exposure of visible light was minimal in iodide-treated solar cells. Transient absorption measurements provide insight into the influence of light exposure on charge carrier recombination processes in mixed halide perovskite films. The iodide treatment strategy presented here can aid in designing stable mixed halide perovskite solar cells and the development of multijunction solar cells.