Supersaturation-Controlled Growth of Monolithically Integrated Lead-Free Halide Perovskite Single-Crystalline Thin Film for High-Sensitivity Photodetectors.

Abstract

Monolithical integration of the promising optoelectronic material with mature and inexpensive silicon circuitry contributes to simplifying device geometry, enhancing performance, and expanding new functionalities. Herein, a lead-free halide perovskite Cs₃ Bi₂ I₉ single-crystalline thin film (SCTF), with thickness ranging from 900 nm to 4.1 µm and aspect ratio up to 1666, is directly integrated on various substrates including Si wafer, through a facile and low-temperature solution-processing method. The growth kinetics of the lead-free halide perovskite SCTF are elucidated by in situ observation, and the solution supersaturation is controlled to reduce the inverse-temperature crystallization nucleation density and elongate the evaporation growth. The excellent lattice match and band alignment between Si(111) and Cs₃ Bi₂ I₉ (001) facets promote photogenerated charge dissociation and extraction, resulting in boosting the photoelectric sensitivity by 10-200 times compared with photodetectors based on other substrates. More importantly, this silicon-compatible perovskite SCTF photodetector exhibits a high switching ratio of 3000 and a fast response of 1.5 µs, which are higher than most reported state-of-the-art lead-free halide perovskite photodetectors. This work not only gives an in-depth understanding of the perovskite precursor solution chemistry, but also demonstrates the great potential of monolithical integration of lead-free halide perovskite SCTF with a silicon wafer for high-performance photodetectors.