v>Light activation is an effective method to improvesensor performance at room temperature (RT). This work realizedthe effective detection of trace-level NO2at RT under visible lightby combining ZnO with the excellent photocatalyst BiOI. A 1.5atom % BiOI−ZnO-based sensor under 520 nm light exhibitedoptimal sensing properties with the maximum responses (13.9 to 1ppm NO2), fast response/recovery time (66 s/47 s to 1 ppm), anda low detection limit of 25 ppb (theoretically 0.34 ppb). In themeantime, the sensor also possessed excellent selectivity,repeatability, and stability. The excellent properties were attributedto the high concentration of oxygen vacancies and the prolongedlifetime of photogenerated carriers. In addition, the observedphotovoltaic effect of the sensor at RT indicated that the sensor held application prospects in the photovoltaic self-power field.