Lead-free perovskite Cs2AgBiBr6 epitaxial thin films for high-performance and air-stable photodetectors

Abstract

Photodetectors that employ lead halide perovskite semiconductor crystals or polycrystalline films show great promise for applications in both visible and X-ray spectra. Nonetheless, the processing of large-sized crystals, the stability of polycrystalline perovskite films and the inherent toxicity of these materials hinder the practical implementation of such photodetectors. For most semiconducting devices epitaxial thin films are preferred, such as commercial infrared photodetectors based on InGaAs epitaxial films. Moreover, epitaxial films of halide perovskites have demonstrated supercarrier dynamics, high optoelectronic performance, and better phase stability than their polycrystalline counterpart. In this paper, we introduce pulsed laser deposition (PLD) as a method for the epitaxial growth of lead-free Cs₂AgBiBr₆ thin films on conventional oxide perovskite SrTiO₃(100) substrates. Capitalizing on the exceptional quality of these epitaxial films, Cs₂AgBiBr₆-based photodetectors have shown a remarkable responsivity of 12.1 A W⁻¹, a low detection limit of 4.63 × 10¹² Jones, and rapid response speeds of 0.11/0.16 ms. Notably, the unencapsulated epitaxial Cs₂AgBiBr₆ film photodetectors exhibit exceptional stability even in ambient air. Our research underscores the outstanding photoelectric properties of epitaxial lead-free halide perovskite thin films, positioning them as a foundation for the exploration of a variety of high-performance and environmentally sustainable optoelectronic devices.