Recent Advances in Halide Perovskite Single‐Crystal Thin Films: Fabrication Methods and Optoelectronic Applications

Metal‐halide perovskites have aroused intense interest in the scientific community by virtue of their numerous remarkable optoelectronic properties, which render them promising candidates for applications in various optoelectronic fields, such as solar cells, light‐emitting diodes, photodetectors, and lasers. Compared with perovskite polycrystalline films and nanocrystals, grain‐boundary‐free single‐crystal perovskites possess lower trap‐state densities, higher carrier mobilities, and longer diffusion lengths, which are supposed to deliver superior optoelectronic performance. However, the thickness (a few millimeters) of typical bulk single‐crystal perovskites are much greater than their carrier diffusion length (e.g., MAPbI 3 SC, ≈175 µm), which results in severe charge accumulation and significantly hinders their development. To this end, fabricating single‐crystal thin films is of great importance for further exploring the potential of single‐crystal perovskites in various applications. In this paper, the rapid and prosperous developments in the fabrication methods of perovskite single‐crystal thin films are systematically summarized and recent encouraging progress in their physical and chemical properties as well as the optoelectronic applications (solar cells, photodetectors, and light‐emitting diodes) of single‐crystal thin films are reviewed. Finally, the challenges and a brief outlook for further improving the quality of perovskite single‐crystal thin films and optimizing the device design are highlighted.