Narrow Bandgap Metal Halide Perovskites: Synthesis, Characterization, and Optoelectronic Applications

Abstract Traditional semiconductor materials with narrow bandgap are involved in a wide range of important applications such as photodetection, photovoltaics, biosensing, and bioimaging. Recently, narrow bandgap metal halide perovskites (MHPs) have attracted widespread attention with the advantages of low cost, easy synthesis, adjustable bandgap, and high photoluminescence quantum yield. State‐of‐the‐art progress of narrow bandgap MHPs is reviewed with emphasis on the structures, synthesis methods, characterizations, and optoelectronic applications. First, the structures and classifications of different dimensions of narrow bandgap MHPs are introduced. On this basis, a variety of synthetic and stability enhancement strategies of common narrow bandgap MHPs are discussed. Second, the applications of narrow bandgap MHPs for photodetectors, light‐emitting diodes, lasers, sensors, and memories are reviewed. Finally, the authors provide a perspective of current challenges in long‐term stability and fundamental properties, and propose new opportunities for broader fundamental researches and practical applications in the outlook section.