Blue-green emitting KCsPbBr3 quantum dots-Sr2MgSi2O7: Eu2+ phosphor composite for optical information encoding and full-spectrum white light emission

Red-Green-Blue (RGB) phosphors are promising for optical information encoding and full-spectrum white light-emitting diodes (WLEDs). Herein, KCsPbBr 3 perovskite quantum dots (PQDs, ∼5.0 nm) were successfully formed on Sr 2 MgSi 2 O 7 : Eu 2+ phosphors via a facile deposition–precipitation method, yielding blue-green emitting composites. The KCsPbBr 3 -Sr 2 MgSi 2 O 7 : Eu 2+ composites exhibit tunable emissions at 463 nm and 519 nm under 365 nm excitation. Specifically, the blue emission at 463 nm is attributed to the 4f 6 5 d 1 → 4f 7 transition of Eu 2+ ions in the Sr 2 MgSi 2 O 7 host, while the green emission at 519 nm originates from the emission of KCsPbBr 3 perovskite quantum dots. Notably, the emission intensity at 75 wt% KCsPbBr 3 is ∼240 times higher than that at 9 wt% and a blue afterglow persists after removing UV excitation. Under external stimulation, the composites display color-variable patterns with fluorescence mode conversion, enabling multi-dimensional anti-counterfeiting. For instance, an RGB pattern appears white under natural light but transforms into a red-green pattern under UV and afterglow modes. Furthermore, full-spectrum WLEDs with high color rendering (Ra = 90, Rf = 83, Rg = 91), comparable to sunlight, are achieved by combining the composites with CaAlSiN 3 : Eu 2+ . These results indicate that KCsPbBr 3 -Sr 2 MgSi 2 O 7 : Eu 2+ PQD phosphors have strong potential in advanced anti-counterfeiting and full-spectrum WLED applications.