Organometallic-Based Hybrid Perovskite Piezoelectrics with a Narrow Band Gap

Hybrid organic-inorganic perovskites (HOIPs) with the general formula ABX₃ hold phenomenal research interest for their great scientific and technological potential in photovoltaic, piezoelectric, and electroluminescent devices. It is their considerable structural diversity that offers a good opportunity to build a variety of HOIP structures with various functionalities. However, no organometallic-based HOIP piezoelectrics have yet been found, despite the structural diversity and functional richness of organometallic compounds such as the ferrocene-based family. Here, for the first time, we report an organometallic-based HOIP piezoelectric, [(ferrocenylmethyl)trimethylammonium]PbI₃. Benefitting from the stability of ferrocene-based cations, excellent piezoelectric performance, comparable to that of LiNbO₃, can be obtained and optimized by tuning the anionic framework. The involvement of organometallic cations enables a narrow band gap of 2.37 eV, much lower than those of most HOIPs and some inorganic semiconductors. This work provides a new future direction for the study of perovskites and will inspire intriguing research on organometallic-based HOIP piezoelectrics.