military and daily life. [1] Various widebandgap semiconductors with diverse morphologies [2] and nanostructures, [3] have been developed for SBUV PDs. Recently, photoelectrochemical-type (PEC) PDs have been booming due to the low-cost fabrication, low-quality requirement of materials, good self-powered capability, and high sensitivity. [4] Compared with traditional solid-state SBUV PDs, PEC SBUV PDs not only depend on the internal charge transport of semiconductors but also rely on the charge transfer at the interface between semiconductors and electrolyte, offering more freedom to regulate the photoresponse performance. Several widebandgap semiconductors with various nanostructures, such as Ga 2 O 3 nanorods [5] and AlGaN nanowires, [6] have been investigated for PEC SBUV PDs. However, the corresponding photoresponse is much lower than expected. Several strategies have been proposed to improve the performance of PEC SBUV PDs, such as surface modification of noble metal nanoparticles [6b,c] and the construction of core-shell heterojunctions, [7] which inevitably increase the fabrication cost. Therefore, it is attractive to explore alternative and low-cost strategies for promoting the photoresponse of PEC SBUV PDs.Tin oxide (SnO 2 ) is an n-type wide-bandgap (E g = 3.6 eV) semiconductor with the merits of superior electron transport properties and good stability in the environment, [8] endowing SnO 2 an attractive candidate for gas sensors, [9] electrocatalysts, [10] solar cells, [11] lithium-ion batteries, [12] and SBUV PDs. [13] Traditional solid-state SBUV PDs based on various SnO 2 nanostructures [14] and heterojunctions [15] have been exploited with good performance, certainly demonstrating their potential application in UV PDs. However, PEC SBUV PDs based on individual SnO 2 nanostructures have rarely been investigated. [16] Most studies focus on utilizing the good electron transport properties of SnO 2 to improve the photoresponse of other wide-bandgap semiconductor-based PEC SBUV PDs (such as TiO 2 and ZnO) [17] by constructing heterostructures. Although SnO 2 nanoparticles-based PEC PDs have been investigated, they show poor photoresponse with a low responsivity Tin oxide (SnO 2 ) 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 SnO 2 -based photoelectrochemical (PEC)-type SBUV PDs. In this study, oxygen vacancies (OVs) engineering is proposed to manipulate the photoresponse of SnO 2 nanosheets (NSs) and high-performance SnO 2 -based PEC SBUV PDs are developed. SnO 2 NSs with different OVs are prepared by hydrothermal method with annealing process. PEC PDs consisting of SnO 2 NSs annealed at 550 °C show record high responsivity and specific detectivity of 269.40 mA W −1 and 2.38 × 10 12 Jones at a bias voltage of 0.2 V, respectively, surpassing all aqueous-type PEC UV PDs. OVs simulta...