Vertical MSM-Type CsPbBr₃ Thin Film Photodetectors with Fast Response Speed and Low Dark Current

Abstract

Halide perovskites exhibit excellent electrical and optical properties, which are ideal active layer candidates for optoelectronic devices, particularly in high-performance photodetection where they demonstrate a competitive edge in development prospects. Among these, the all-inorganic perovskite CsPbBr₃ has garnered widespread attention due to its better environmental stability. This paper demonstrated a vertical MSM-type CsPbBr₃ thin-film photodetector characterized by fast response times and ultra-low dark current. The use of a vertical structure reduces the transit distance of photo carriers, enabling the device to achieve a fast response time of 63 μs, which is an improvement by two orders of magnitude compared to the traditional planar MSM-type photodetectors with response times of 10 ms. Then, by spinning a charge transport layer between the p-type CsPbBr₃ and Ag electrodes, photocarriers effective separation at interface is realized and physical passivation between the perovskite and metal electrodes is also achieved. Due to the superior surface quality of the spun TiO₂ film compared to the NiO_X film, and through Sentaurus TCAD simulations and bandgap analyses, with TiO₂ serving as the electron transport layer, it effectively inhibits the transmission of excess holes in p-type CsPbBr₃. Consequently, the electron transport layer TiO₂ is more effective at reducing dark current than the hole transport layer NiO_X, with a dark current magnitude of only -4.81×10^-12 A at a -1 V bias. Furthermore, this vertical MSM-type CsPbBr₃ thin-film photodetector also boasts a large linear dynamic range (122 dB), high detectivity (1.16×10¹² Jones), and good photo-stability. Through Sentaurus TCAD simulation, it was found that the charge transport layer selectively blocks carrier transmission, thereby reducing dark current. The simulation results are in good agreement with experimental data, providing theoretical guidance for a deeper understanding of the intrinsic physical mechanisms.