Ultrafast Response of Centimeter Scale Thin CsPbBr Single Crystal Film Photodetector for Optical Communication.

The photodetector (PD) is the key component to realize efficient optoelectronic conversion signal in the visible light communication (VLC) system. The response speed directly determines the bandwidth of the whole system. Metal halide perovskite is a neotype of low-cost solution processing semiconductor, with strong optical absorption, low trap density, and high carrier mobility, thus has been widely explored in photoelectric detection applications. However, previously reported perovskite polycrystalline photodetectors exhibit limited response speed due to the existence of grain boundaries. Here, an improved confined space method is developed through adjusting the heating area to control nucleation, resulting in centimeter scale fully inorganic perovskite CsPbBr thin single crystal films (SCFs) (<40 µm). The smooth surface and high crystallinity of CsPbBr SCFs render admirable exciton lifetime. The planar metal-semiconductor-metal photodetector using CsPbBr SCF as the photosensitive layer demonstrates a limit response time of 200/300 ns and a VLC within 100-500 kHz frequency for both 365 nm and white light, which is superior to previously reported CsPbBr polycrystalline film and single crystal photodetectors.