Vacuum‐Based Monolithically In Situ Integration of Quantum‐Confined CsPbBr 3 Nanocrystals for Spectrally Stable Blue Electroluminescence

ABSTRACT Spectrally stable blue emission represents one of the most critical components of full‐color perovskite displays, which are highly attractive for display technologies. However, vapor‐deposited blue perovskite light‐emitting diodes have so far relied predominantly on Br/Cl mixed‐halide bandgap engineering, which is prone to halide migration and phase segregation under operation and therefore suffers from spectral instability. Here, we report spectrally stable vapor‐deposited, pure‐bromide blue perovskite light‐emitting diodes with spectrally stable emission achieved via a ligand‐buffered delayed nucleation (LBDN) strategy. In this method, p‐Br‐MBABr is co‐deposited as a kinetic buffer to create a ligand‐coordinated precursor state that suppresses immediate crystallization, delays nucleation, and confines subsequent crystal growth. As a result, we obtain quantum‐confined CsPbBr 3 nanocrystal films with tunable blue emission. Fully vapor‐deposited PeLEDs based on these films deliver spectrally stable pure‐blue electroluminescence. These results establish kinetic buffering as an effective route to quantum‐confined perovskites under vapor deposition and spectrally stable blue emitters for monolithically integrated full‐color perovskite displays.