Near‐Unity Quantum Yield and Superior Stable Indium‐Doped CsPbBrxI3−x Perovskite Quantum Dots for Pure Red Light‐Emitting Diodes

Abstract Although all‐inorganic CsPbBr x I 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 In 3+ ‐doped CsPbBr x I 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. In 3+ ion doping not only reduces the surface vacancy defects because of the partial substitution of Pb 2+ by the smaller radii of In 3+ ions, but also enhances the formation energy of CsPbBr x I 3− x PeQDs based on first‐principles calculations. Compared with pristine LEDs based on CsPbBr x I 3− x , the pure red PeLEDs based on In 3+ ‐doped CsPbBr x I 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 In 3+ ‐doped CsPbBr x I 3− x PeQDs applied efficiently in advanced light emitters for solid‐state lighting and displays.