Halide Tunable Perovskite Single Crystals as Efficient Photodetector

Abstract Lead‐free perovskite single crystals (SCs) have made great progress in the field of optoelectronics. However, the desired large‐size Cs₃Bi₂X₉ SCs (X = I/Br/Cl) with fast growth and high quality are still a great challenge. In this study, millimeter‐sized Cs₃Bi₂X₉ SCs) are first prepared within 3 days by synergistic nucleation and supersaturation engineered method in a low‐temperature solution of ≈ 50 °C, which owns unprecedented advantages such as easily tunable different X element and fast growth period. Combined with the dynamics and thermodynamics of crystal growth, a layered growth model of Cs₃Bi₂Br₉ (CBI) SCs is proposed through in situ observation of CBI SCs growth. The carrier dynamic behaviors of three different Cs₃Bi₂X₉ SCs are investigated by ultrafast femtosecond transient absorption (fs‐TA). Furthermore, the electron transport dynamic of the (001) and (100) crystal faces of Cs₃Bi₂Br₉ (CBB) is demonstrated by density functional theory calculations, evidencing the crystal facet‐dependent photoelectrical performance. What's more, optical imaging sensor based on 36 pixels Cs₃Bi₂Br₉ photodetector with ultrahigh on/off ratio of 5909 and optical communication compiled with Morse code is achieved. This strategy to synthesize the CBX SCs is both conceptually simple and synthetically rapid, offers great potential for the development of free‐Pb perovskite single crystals.