Engineering stable and efficient CsPbBr3 nanocrystals via K+ and Mn2+ co-doping for advanced LED and imaging application

All-inorganic CsPbBr3 nanocrystals (CNCs) show great potential in backlight WLEDs and anti-counterfeiting. In this study, structural and compositional analyses including x-ray diffraction, transmission electron microscopy, and x-ray photoelectron spectroscopy confirm that Mn2+ substitutes Pb2+ and K+ replaces Cs+ within the lattice, optimizing energy level alignment and carrier distribution while maintaining the cubic perovskite phase. Density functional theory calculations reveal that K+ incorporation does not introduce defect states, whereas Mn2+ introduces shallow defect levels. Time-resolved photoluminescence measurements indicate that co-doping with K+ and Mn2+ synergistically improves carrier lifetime by reducing nonradiative recombination. The co-doped CNCs exhibit a significant enhancement in the external quantum efficiency, increasing from 32.47% (pristine) to 52.47% under 365 nm excitation. When integrated into a backlight white LED, combining K+/Mn2+-doped CNCs with commercial KSF red phosphors on a 445–450 nm blue LED chip, the device achieves a wide color gamut covering 131.9% of the National Television System Committee (NTSC) and 98.5% of the Rec.2020 standards—outperforming conventional phosphor-based systems. Additionally, the co-doped CNCs embedded in PVC-based inks generate high-resolution fluorescent anti-counterfeiting patterns that retain optical clarity after 288 h of UV aging. This work demonstrates that rational ion substitution via co-doping is an effective strategy to enhance both the optoelectronic performance and long-term stability of CNCs, advancing their integration into the next-generation display and security technologies.