Lead halide perovskite nanocrystals (NCs) have been the star material in lighting and displays owing to their excellent photoelectrical properties, but they have not simultaneously realized high photoluminescence quantum yield (PLQY) and high stability. To solve this problem, we propose a perovskite/linear low-density polyethylene (perovskite/LLDPE) core/shell NC by the synergistic role of the pressure effect and steric effect. Green CsPbBr3/LLDPE core/shell NCs with near-unity PLQY and nonblinking behavior were synthesized through an in situ hot-injection process. The mechanism of the improved photoluminescence (PL) properties is the enhanced pressure effect resulting in increased radiative recombination and interaction between the ligand and perovskite crystals, as confirmed by the PL spectra and finite element calculations. Meanwhile, the NCs show high stability under ambient conditions (with a PLQY of 92.5% after 166 days) and against 365 nm UV light (maintaining 61.74% of the initial PL intensity after continuous radiation for 1000 min). This strategy also works well in the blue and red perovskite/LLDPE NCs and red InP/ZnSeS/ZnS/LLDPE NCs. Finally, white-emitting Mini-LEDs were fabricated by combining the green CsPbBr3/LLDPE and red CsPbBr1.2I1.8/LLDPE core/shell NCs with blue Mini-LED chips. The white-emitting Mini-LEDs exhibit super wide color gamut (∼129% of the National Television Standards Committee or 97% of the Rec. 2020 standards).
Keywords: nanocrystals; perovskite; photoluminescence; pressure effect; stability.