Stable Lead-Free Cesium Tin Halide Double-Perovskite Nanocrystals Embedded in Polydimethylsiloxane for Candlelight Light-Emitting Diodes

In this study, lead-free cesium tin halide (Cs2SnBr6) double-perovskite nanocrystals (DPNCs) were synthesized and investigated using an easy hot-injection method. Hexagonal-shaped Cs2SnBr6 DPNCs, having cubic symmetry with the Fm3̅m space group, were exhibited for the first time through X-ray diffraction and Raman experiments. The bandgap structures and photoluminescence (PL) mechanism of self-trapped excitons in the Cs2SnBr6 DPNCs were experimentally demonstrated by X-ray photoelectron and ultraviolet (UV)–visible absorption spectroscopy. The prepared Cs2SnBr6 DPNCs had an average size of approximately 58 nm and generated orange emission at a wavelength of 600 nm (full-width at half-maximum, 121 nm). These samples exhibited a PL quantum yield of approximately 31% and fluorescence lifetime of approximately 3.3 μs. The Cs2SnBr6 DPNCs and blue phosphor (Sr5(PO4)3Cl:Eu2+) were mixed with polydimethylsiloxane packaging in 365 nm UV light-emitting diodes (LEDs), which were used to fabricate candlelight LEDs with a color-rendering index of 84 and a correlated color temperature of 2006 K. All these results can significantly contribute to the global use of low-toxicity and environmentally friendly luminescent materials for lighting sources.