Achieving High Responsivity of Photoelectrochemical Solar‐Blind Ultraviolet Photodetectors via Oxygen Vacancy Engineering

Abstract Tin oxide (SnO₂) is an n‐type wide‐bandgap semiconductor with the merits of superior electron transport properties and good stability, making it an attractive candidate for solar‐blind ultraviolet photodetectors (SBUV PDs). However, it is still challenging to design high‐performance SnO₂‐based photoelectrochemical (PEC)‐type SBUV PDs. In this study, oxygen vacancies (OVs) engineering is proposed to manipulate the photoresponse of SnO₂ nanosheets (NSs) and high‐performance SnO₂‐based PEC SBUV PDs are developed. SnO₂ NSs with different OVs are prepared by hydrothermal method with annealing process. PEC PDs consisting of SnO₂ NSs annealed at 550 °C show record high responsivity and specific detectivity of 269.40 mA W⁻¹ and 2.38 × 10¹² Jones at a bias voltage of 0.2 V, respectively, surpassing all aqueous‐type PEC UV PDs. OVs simultaneously accelerate the carrier recombination in the SnO₂ NSs and charge transfer at the interface of the SnO₂ NSs and electrolyte, indicating that both excess OVs and too few OVs reduce the PEC photoresponse. Therefore, an appropriate OV's content is vital to designing high‐performance SnO₂ NSs PEC PDs. Moreover, the SnO₂ NSs PEC PDs have good self‐powered capability, excellent wavelength‐selectivity, multicycle and long‐term stability. The results of this study demonstrate that OVs engineering is a powerful strategy for designing high‐performance SnO₂‐based PEC PDs.