Self-powered flexible humidity sensors based on amorphous boron arsenide nanosheets

Boron arsenide, renowned for its ambipolar charge mobility and superior thermal conductivity, has emerged as a focal point of contemporary research. Despite its promising properties, the impact of water on the electronic conductivity (EC) of boron arsenide remains largely unexplored. In this study, we synthesized amorphous boron arsenide (<em>a</em>-BAs) nanosheets through an innovative in situ reaction involving elemental arsenic and sodium borohydride within a low-pressure, hydrogen-rich environment. We performed both theoretical and experimental analyses to investigate the influence of water on EC in representative <em>a</em>-BAs. These nanosheets were integrated into self-powered, flexible humidity sensors, demonstrating a substantial current change across nearly five orders of magnitude and achieving an extraordinary response of 8.4 × 10⁶% at 85% RH without an additional power unit. The sensors exhibited a remarkable linear correlation between the logarithmic response function and a wide-ranging detection capability (11-97% RH), achieving an extraordinary response of 1.4 × 10⁶% at 97% RH under a 1 V bias. This research not only introduces a straightforward synthesis method for amorphous boron arsenide nanosheets but also highlights the significant impact of water on the EC of boron arsenide, paving the way for developing self-powered high-performance sensing materials.