Bright Luminescence from Nontoxic CsCu₂X₃ (X = Cl, Br, I)

Inexpensive and highly efficient luminescent materials based on multinary halides have received increased attention in recent years. Among those considered most promising are the perovskites such as CsPbX3 because of their highly efficient and tunable emission through precise control of chemical composition and nanostructuring. However, the presence of the toxic heavy metal Pb and relatively poor stability are among the major challenges for the introduction of lead-halide-based materials into the marketplace. Here, we report the optical properties of nontoxic and highly emissive one-dimensional (1D) all-inorganic halides CsCu2X3 (X = Cl, Br, I) and their mixed halide derivatives, which also show improved thermal and air stability. Photoluminescence (PL) measurements show tunable bright room temperature emission from green to yellow with photoluminescence quantum yields ranging from 0.37 (CsCu2Cl1.5Br1.5) to 48.0% (CsCu2Cl3). Temperature- and power-dependent PL measurements suggest that the emission results from self-trapped excitons induced by strong charge localization and structural distortions within the lD ribbon structure

High-Detectivity UV–Vis–NIR Broadband Perovskite Photodetector Using a Mixed Pb–Sn Narrow-Band-Gap Absorber and a NiO<i>_x</i> 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