Flexible, self-powered UVC photodetectors enabled by low-temperature solution-processed SnO2 : PEI nanocomposites

Abstract

Wearable ultraviolet-C photodetectors (UVC PDs) are increasingly explored for flame sensing, discharge detection, and secure communication. However, their development is constrained by the requirement for high-quality and durable thin films, which typically require high-temperature or vacuum-based processes incompatible with flexible substrates. Herein, we present a simple, low-temperature spin-coating method to fabricate UVC-sensitive thin films using wide-bandgap SnO₂ nanoparticles (NPs). Highly transparent polyethyleneimine (PEI) was incorporated to modulate film morphology and enhance the electrical properties of the SnO₂ photoabsorber. The resulting SnO₂ : PEI film exhibited improved compactness and uniformity, which enhanced charge transport and minimized carrier recombination. Integrated into an asymmetric metal–semiconductor–metal structure, the device operated under self-powered conditions and exhibited a competitive performance (responsivity of 1.23 mA W⁻¹, and detectivity of 9.71 × 10¹⁰ Jones), along with excellent selectivity toward UVC radiation. Furthermore, it demonstrated outstanding mechanical stability, with only 2.7% performance degradation under a bending angle of 90°. These findings offer a practical approach for producing flexible and lightweight UVC photodetectors using solution-processed nanocomposites.