Vacuum-Based Monolithically In Situ Integration of Quantum-Confined CsPbBr3 Nanocrystals for Spectrally Stable Blue Electroluminescence.

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 CsPbBr3 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.