High-Detectivity UV–Vis–NIR Broadband Perovskite Photodetector Using a Mixed Pb–Sn Narrow-Band-Gap Absorber and a NiO_x Electron Blocker

Visible and near-infrared broadband photodetectors with multispectral photosensitivity from 300 to 1100 nm were fabricated using the low-band-gap mixed Pb–Sn halide perovskites. A solution-processed nickel oxide (NiOx) thin film was used as the electron-blocking layer in the mixed Pb–Sn low-band-gap perovskite photodetector instead of the commonly used PEDOT:PSS because NiOx has a wider band gap and a shallow conduction band edge compared to PEDOT:PSS. There is no significant difference in the film qualities such as surface roughness, grain size, and crystallinity between polycrystalline perovskite films formed on PEDOT:PSS and NiOx. A NiOx electron blocker significantly reduces (more than 100 times) the dark currents of perovskite photodetectors without sacrificing the photocurrent extraction, resulting in a 10-fold increase in detectivity. Finally, mixed Pb–Sn halide perovskite photodetectors with NiOx as an electron blocker show the detectivity value higher than 1 × 1012 Jones from 320 to 1020 nm and the maximum detectivity value of 5 × 1012 Jones at the peak wavelength of 940 nm. This is comparable with the detectivity values of the commercially available silicon-based visible and near-infrared broadband photodetectors.