A transparent, self-powered photodetector based on p-CuI/n-TiO ₂ heterojunction film with high on–off ratio

Ultraviolet(UV) photodetectors(PDs) can monitor UV radiation, enabling it to be effective for many applications, such as communication, imaging and sensing. The rapid progress on portable and wearable optoelectronic devices places a great demand on self-powered PDs. However, high-performance self-powered PDs are still limited. Herein we display a transparent and self-powered PD based on a p-CuI/n-TiO 2 heterojunction, which exhibits a high on–off ratio ( ∼ 10 4 at 310 nm) and a fast response speed (rise time/decay time = 0.11 ms/0.72 ms) without bias. Moreover, the device shows an excellent UV-selective sensitivity as a solar-blind UV PD with a high UV/visible rejection ratio ( R 300 nm / R 400 nm = 5.3 × 10 2 ), which can be ascribed to the wide bandgaps of CuI and TiO 2 . This work provides a feasible route for the construction of transparent, self-powered PDs based on p–n heterojunctions.