Interface Engineering with Bifunctional Addictive for Efficient and Stable Blue Perovskite LED From In Situ Formed Cs ₄ PbBr ₆ Heterostructured CsPbBr ₃ Quantum Dots

Abstract Quantum‐confinement‐based blue CsPbBr 3 perovskite quantum dots (PeQDs) have attracted significant research interest in light‐emitting diodes (LEDs) due to their outstanding optoelectronic properties, solution‐processability, and free from spectral separation. However, their performance lags behind due to low film quality, high trap density, and mismatched carrier transporting. To address these issues, a bifunctional‐additive interface engineering is proposed on in situ formed blue Cs 4 PbBr 6 heterostructured CsPbBr 3 (CsPbBr 3 @Cs 4 PbBr 6 ) PeQDs. The introduction of glycine, with an amino group and a carboxyl group, enables the PeQD film high surface uniformity and photoluminescence quantum yield up to 51.6% from mere 14.1% with a peak wavelength at 489 nm, but low trap density and matched transporting of electron and hole. Surprisingly, glycine‐treated PeQD films show significantly enhanced stability against air and ultraviolet lamp exposure. Experimental results and density functional theory calculations reveal that the carboxyl group contributes to maintaining the quantum confinement effect, while the amino group promotes optical emission due to its strong binding ability. Furthermore, the resulting CsPbBr 3 @Cs 4 PbBr 6 PeQD‐based LEDs demonstrate outstanding performance, with an increase by a factor of 10 in external quantum efficiency to 5.8% and of 13 in operating life to 405 s. This study offers a straightforward approach for developing high‐performance blue PeQD LEDs.