Lattice‐Matched BaClF/CsPbBr3 Heterostructure with Enhanced and Stable Cyan Emission to Overcome Blue Overshoot and Cyan Gap of White Light‐Emitting Diodes

Abstract Combining blue‐emitting LED chip and yellow‐emitting phosphor coating is efficient in manufacturing white light‐emitting diode (WLED). However, the lack of a uniformly distributed continuous emission spectrum in conventional WLED can result in “blue overshoot” and “cyan gap”, thus cause retinal damage and low color rendering index (CRI). Herein, a novel “kill two birds with one stone” strategy is reported: by preparing BaClF/CsPbBr 3 heterostructures via a lattice‐ matching approach, F and Cl in BaClF matrix passivate the bromine vacancies of CsPbBr 3 NCs, enhancing luminescence stability and achieving a blue‐shift of PL to obtain cyan‐emission. BaClF/CsPbBr 3 heterostructures with controllable emissions in 468–510 nm can be fabricated by adjusting the molar ratios of CsPbBr 3 to BaClF, and the photoluminescent quantum yield (PLQY) is up to 80.6%. The cyan‐emitting BaClF/CsPbBr 3 heterostructure acting as a cyan color converter can effectively absorb the “blue overshoot” and fill the “cyan gap” in WLED, thus significantly increasing the CRI value of WLED from 70.1 to 86.2 and the luminescent efficiency boosts from 21.3 to 87.8 lmW −1 . This work highlights a lattice‐matching strategy to produce ultra‐stable cyan‐emitting perovskite nanomaterials with high brightness and durability, paving the way for the application of perovskite NCs in next‐generation WLED lighting.