Near‐Unity Quantum Yield and Superior Stable Indium‐Doped CsPbBr_xI_3−x Perovskite Quantum Dots for Pure Red Light‐Emitting Diodes

Abstract Although all‐inorganic CsPbBr_xI_3−x perovskite quantum dots (PeQDs) are increasingly being used as a competitive material for pure red perovskite light‐emitting diodes (PeLEDs), they suffer from low luminescent ability and poor stability. In this study, an In³⁺‐doped CsPbBr_xI_3−x PeQD solution exhibits a near‐unity photoluminescence quantum yield (PLQY) of ≈99.8% and superior stability for more than half a year in atmosphere. As far as known, this is the highest PLQY and stability achieved for mixed halide PeQDs. In³⁺ ion doping not only reduces the surface vacancy defects because of the partial substitution of Pb²⁺ by the smaller radii of In³⁺ ions, but also enhances the formation energy of CsPbBr_xI_3−x PeQDs based on first‐principles calculations. Compared with pristine LEDs based on CsPbBr_xI_3−x, the pure red PeLEDs based on In³⁺‐doped CsPbBr_xI_3−x display a higher luminance of 423 cd m^‐2, fivefold external quantum efficiency improvement up to 11.2%, and increased stability, providing a feasible and promising perspective for developing In³⁺‐doped CsPbBr_xI_3−x PeQDs applied efficiently in advanced light emitters for solid‐state lighting and displays.