Mixed Halide Perovskite Solar Cells: Progress and Challenges

Single and mixed-halide perovskite solar cells (PSCs) have attracted a lot of research attention in recent years due to their solution process-ability, lightweight and excellent photoelectric conversion which are the necessary conditions for low-cost thin-film solar cell technology. The power conversion efficiency (PCE) of solid-state PSCs has risen quickly to a certified value as high as 22%. There is still tremendous potential for the realization of highly efficient solution processable perovskite-based solar cell. The perovskite produced by way of mixing halogen elements, such as CH3NH3PbI3-xClx and CH3NH3PbI3-xBrx, offered several benefits such as enhanced device stability, improved carrier transport and reduced carrier recombination. Single crystal perovskite film containing organic and inorganic cation reported to have broad optical absorption which covers significant part of the solar spectrum. It also exhibited good thermal stability compared to single halide such as CH3NH3PbI3. The device configuration of PSCs and the choice of suitable hole/electron transport materials played a significant role in the device performances. This review article reports on the recent advances of solution processed PSC with emphasis on the role played by mixed halide elements on the performance of devices.