Sb3+/Ln3+ Co-Doping Enables Color-Tunable and High-Efficiency White-Light Emission in Cs2NaYCl6 Double Perovskite Microcrystals

In this study, a series of single-, double-, and triple-doped rare-earth halide double perovskite microcrystals, specifically Sb³⁺- and Ln³⁺-doped (Ln³⁺ = Er³⁺, Ho³⁺) Cs₂NaYCl₆, were successfully synthesized via a solvothermal method. In Cs₂NaYCl₆:Sb³⁺ microcrystals, the incorporation of Sb³⁺ ions effectively relaxes the parity-forbidden transitions, resulting in a substantial enhancement of the photoluminescence quantum yield (PLQY) from 11.15 to 77.55%, along with prominent blue emission. Moreover, codoping with Er³⁺ and Ho³⁺ ions enables a continuous color transition, driven by efficient energy transfer between self-trapped excitons (STEs) and the rare-earth dopants. This leads to a progressive shift from blue (STEs) to green (Er³⁺) and ultimately to red (Ho³⁺) emission. Such remarkable color tunability facilitates the creation of a single-source white-light phosphor, achieving well-defined CIE chromaticity coordinates of (0.3482, 0.2894) and a stable correlated color temperature (CCT) of 4531 K. Notably, the emission spectrum closely approximates ideal white light, highlighting its significant potential for optoelectronic applications, particularly in white-light-emitting diodes (WLEDs). The codoping strategy with Sb³⁺ and rare-earth ions not only enhances luminescence efficiency but also advances the development of high-performance, environmentally friendly phosphor materials, paving the way for next-generation optoelectronic devices.