Local stress enhanced photocurrent of visible light photo-detection in Cs2AgBiBr6 single crystal

Halide perovskites have attracted worldwide attention in recent years due to their fundamental scientific importance and practical applications in energy harvesting fields. However, its toxicity and instability are hindering the commercial applications of halide perovskite-based devices. Recently discovered inorganic lead-free Cs2AgBiBr6 double perovskite exhibits excellent optical and electronic properties and can be considered as a candidate for photovoltaic devices. In this work, we report the photoelectric performance of the Cs2AgBiBr6 single crystal as a photodetector both macro- and microscopically. By utilizing a nanoscale probe as a top electrode, it is discovered that the photogenerated carriers are effectively collected, as in the case of macroscopic electrodes. More importantly, the photocurrent is enhanced as the applied nanoscale mechanical load increases, which indicates that the local bandgap of the Cs2AgBiBr6 single crystal decreases with the increased nanoscale stress, showing similar tendency with the first-principles calculation result. The reported finding establishes a strategy to enhance the performance of photodetectors, which will be a great help in improving the performance of future optoelectronic devices and energy harvesting devices at the nanoscale.