Constructing Sensitive and Fast Lead-Free Single-Crystalline Perovskite Photodetectors.

We developed a high-performance photodetector based on (CH3NH3)3Sb2I9 (MA3Sb2I9) microsingle crystals (MSCs). The MA3Sb2I9 single crystals exhibit a low-trap state density of ∼1010 cm-3 and a long carrier diffusion length reaching 3.0 μm, suggesting its great potential for optoelectronic applications. However, the centimeter single crystal (CSC)-based photodetector exhibits low responsivity (10-6 A/W under 1 sun illumination) due to low charge-carrier collection efficiency. By constructing the MSC photodetector with efficient charge-carrier collection, the responsivity can be improved by three orders of magnitude (under 1 sun illumination) and reach 40 A/W with monochromatic light (460 nm). Furthermore, the MSC photodetectors exhibit fast response speed of <1 ms, resulting in a high gain of 108 and a gain-bandwidth product of 105 Hz. These numbers are comparable to the lead-perovskite single-crystal-based photodetectors.