Cs/FA Gradient Distribution in Perovskite NCs Enables Sub‐Nanometer Spectral Regulation and BT.2020 Pure‐Green Electroluminescence

Lead halide perovskite exhibits great prospects in next‐generation display. However, single‐cation inorganic perovskite nanocrystals (NCs) still suffer from offset gamut coordinates determined by bandgap, short operating life, and low‐efficiency in light‐emitting diodes (LEDs), on account of the limitations in lattice stability and defect levels. Here, a thermodynamic co‐competition strategy is proposed for fabricating Cs1−xFAxPbBr3 NCs, which reveals the spatial distribution of A‐site cations and the improvement of photoelectronic performance. This strategy achieves precise control of NCs in the pure‐green range with an accuracy of sub‐nanometer, further promotes the comprehensively filling‐suppressing effect of incongruous lattice and surface defects. Finally, the high‐precision adjusting in electroluminescence is achieved, and the champion device achieves a CIE coordinate of (0.121, 0.788), meeting the pure‐green range in BT.2020. Simultaneously, the PeLED demonstrates an EQE exceeding 20% with superior stability, accompanied by 20‐fold improvement in lifetime, indicating tremendous potential in next‐generation display. A thermodynamic co‐competition strategy is proposed to synthesize Cs/FA gradient‐distribution Cs1−xFAxPbBr3 nanocrystals, enabling the spectral regulation with sub‐nanometer precision and comprehensively filling‐suppressing the incongruous defects. The devices achieve precise regulation in electroluminescence and ideal pure‐green gamut in BT.2020. The champion device demonstrates an external quantum efficiency exceeding 20%, accompanied by 20‐fold improvement in lifetime.