Metal‐Free Organic Halide Perovskite: A New Class for Next Optoelectronic Generation Devices

Abstract Even though the metal‐halide perovskites are attracting ever‐increasing interest for their breakthrough efficiencies in photovoltaics, light‐emitting diodes (LED), X‐ray imaging, and general optoelectronics, it was not until very recently that metal‐free halide perovskites become recognized, not only for their good optoelectronic performance, but also for their wide chemical diversity, tunability, lightweight, mechanical flexibility, and eco‐friendly processability. The community is turning their attention to these lightweight semiconductors, and promising results have been achieved in the initial evaluation of crystal structure and a range of properties including ferroelectric and optoelectronic properties. In this review, the crystal structure and synthesis of these materials are discussed together with the various properties that have been studied for these materials. Future prospects are further discussed for chemical diversity, structure tunability, synthetic process, potential properties, optoelectronic, and energy‐related applications.