Highly sensitive UV photodetector based on solution-processed bismuth oxyiodide epitaxial thin films

Abstract

Bismuth oxyhalides have attracted much attention in the field of optoelectronics because of their highly anisotropic crystal structure, tunable optical properties, and low toxicity. Few studies on the epitaxial growth of bismuth oxyhalides have been reported so far, however epitaxial thin films are suitable for investigating intrinsic properties and achieving device construction. In this study, we achieved the high quality epitaxial growth of BiOI thin film with thickness on the nanometer scale controllable via the deposition time. The bandgap of the BiOI exhibited a negative corelation with the film thickness owing to the quantum confinement effect. The as-fabricated photodetector based on the optimized thickness of the BiOI film exhibited high optoelectrical performance with a responsivity of 43.5 mA W⁻¹ and normalized detectivity of 8.7 × 10¹⁰ Jones under the illumination of 405 nm laser. Furthermore, the photoresponse mechanism of the BiOI photodetector was tuned from a photoconduction to photogating effect depending on the thickness of the epitaxial thin film. The high crystallinity and continuous surface morphology contribute to the generation of the photogating effect of the BiOI film. This study enriches the investigation of bismuth oxyhalides and paves the way towards the design of efficient bismuth-based semiconductor optoelectronic devices.