The Role of Metal-Semiconductor Interface in Hybrid Perovskite Devices for High-Performance Solid-State Detectors*

Hybrid perovskites have emerged as excellent semiconductors enabling efficient opto-electronic devices. Apart from the intrinsic properties of the semiconductor, interfaces are critical to make a superior device. Here, we use scanning photocurrent microscopy on lateral methylammonium lead triiodide (MAPbI) single crystal devices with commonly used high work function metal and low work function metal contacts to investigate perovskite-metal interfaces. By comparing the spatially resolved photocurrent maps of devices with Au (high work-function metal) to Pb (low work-function metal), we find that a Schottky barrier exists in both cases and the barrier is higher for the Pb/perovskite junction resulting in a lower leakage current. From the decay of the photocurrent profile near the metal contacts, we estimate charge carrier diffusion length to be 9 ± 2 µm. Using this knowledge, we successfully demonstrate a single crystal MAPbI gamma ray detector from which sharp gamma-ray induced pulses are observed. Our study indicates that the interface plays a significant role especially in solid state detector operating at low flux photon counting mode.