Lead-free
halide light-emitting diodes (LEDs) are fabricated using
nontoxic and earth-abundant CsCu2I3 with a strong
yellow emission at a peak wavelength of 568 nm. CsCu2I3-based host–dopant emitters are formed by vacuum thermal
evaporation (VTE) film codeposition process instead of the commonly
used solution-based film deposition process. Using the VTE process,
extremely thin (30 nm) host–dopant emitters have successfully
been formed with the CsCu2I3 dopant and various
organic host molecules. A bright yellow emission with a photoluminescence
quantum yield value of 84.8% is achieved in the 0.5% CsCu2I3-doped halide emitter film due to the successful spatial
localization of charge carriers and excitons using an organic host
with appropriate energy levels to CsCu2I3. With
the further enhancement in charge balance using the cohost system,
a record-breaking lead-free halide LED has been fabricated with an
EQE of 7.4%. The lead-free halide LEDs are also highly stable in the
device operation with LT70 of 20 h at 100 cd/m2.
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 (NiO x ) 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 NiO x 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 NiO x . A NiO x 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 NiO x as an electron blocker show the detectivity value higher than 1 × 10 12 Jones from 320 to 1020 nm and the maximum detectivity value of 5 × 10 12 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.
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