Emergence of melt and glass states of halide perovskite semiconductors

Metal halide perovskites have attracted considerable attention among emerging semiconductors because they can be fabricated at a low cost and have outstanding optoelectronic properties, exhibiting record-breaking performance in photovoltaic, light-emitting and sensing devices. Since the first report of halide perovskites in 1892, studies have predominantly focused on their crystalline state, characterized by long-range atomic order. Introducing the possibility of a melt and/or glass state, devoid of substantial periodicity, unlocks new avenues for property tunability, reminiscent of the transformative impact that chalcogenide glasses have provided for commercial applications, including memory and computing. In this Perspective, we highlight the mounting evidence suggesting that melt and/or glass states of halide perovskites and related hybrids hold substantial promise for expanding the property and application spectrum of this materials family. We provide a comprehensive overview of melt and glass-forming perovskites, underscore pivotal concepts behind generating low-melting-temperature and switchable crystalline or glassy states, and emphasize the crucial importance of investigating these states in the context of structure–property tunability and application.