The halogen chemistry of halide perovskites

The oxygen chemistry of oxide perovskites has been studied for decades, revealing reactivity, transport, and electronic properties enabled by the oxide anion. Similarly, the halide anion dictates the properties and unusual phenomena observed in halide perovskites. Manipulating the halide site has improved the performance and stability of halide perovskites in a range of optoelectronic technologies, most commonly as components in solar cells and light-emitting diodes. Further, the redox activity of the halides allows for controlled electronic doping and halide exchange, as well as for the capture and separation of halogen gases. Herein, we summarize the key aspects of the chemistry of the perovskite halide site. We close with a discussion of pseudohalide perovskites, which hold commonalities with the halide perovskites.