Narrowband photoresponse of a self-powered CuI/SrTiO3 purple light detector with an ultraviolet-shielding effect

The p-CuI/n-SrTiO3 heterojunction photodetector (PD) is constructed based on a SrTiO3 wafer, which is covered with a CuI film via the vacuum thermal evaporation method. Compared with the SrTiO3 (STO) device, the CuI/STO PD exhibits significantly enhanced photocurrent. Furthermore, the CuI/STO PD presents excellent self-powered characteristics, including high on/off ratio (7 × 103) and fast response speed (0.6/3.3 ms) under 400 nm light irradiation. In particular, the CuI/STO PD shows a great narrowband photoresponse (FWHM ∼ 27 nm) at zero bias because of the proper and compatible bandgap of CuI and STO. More importantly, the CuI/STO device demonstrates a transparency of 70% over the entire visible light region and blocks 99.9% UV light (200–385 nm). This work provides an effective strategy to realize power-free, filter-free and UV-free PDs for many special applications.