Full‐Color Gamut White Light Emission From Mn‐doped Cs 3 Cu 2 X 5 Nanocrystals via Lattice Engineering

Abstract Cs 3 Cu 2 X 5 ‐based lead‐free material (X = Cl, Br, and I) nanocrystals (NCs) are promising eco‐friendly materials for various optoelectronic applications. Although manganese (Mn 2+ ) ion doping into Cs 3 Cu 2 X 5 may widen the emission color gamut, incorporating them is challenging because of the robust tetrahedral [CuX 4 ] and triangular [CuX 3 ] structures. This paper addresses this challenge using a lattice engineering strategy, which induces appropriate lattice shrinkage by replacing I − with Cl − in the Cs 3 Cu 2 I 5 NC structure. The promotion effect of Cl − substitution on the Mn 2+ doping is confirmed by structural and chemical analysis, indicating the formation of highly crystalline NCs. The Mn‐doping modifies the electronic structures of Cs 3 Cu 2 X 5 by reducing the band gap energy and forming effective energy transition pathways. The emission range of the NCs is expanded from blue to orange and finally manifest full‐color gamut white light emission. The continuous broad spectrum is attributed to the combined blue emission of self‐trapped excitons and the yellow‐orange emission of the Mn 2+ d–d energy transition. A white light‐emitting diode with Mn‐doped Cs 3 Cu 2 X 5 NCs as a color conversion layer exhibit stable white emission with CIE coordinates of (0.34, 0.32) and a correlated color temperature of 5010 K, closely matching daylight conditions and is applied as an intelligent artificial sunlight.