Multicolor luminescence and afterglow from Cs2NaScCl6:Sb3+,Mn2+ crystals†

In contrast to single-band emitting phosphors, dual-band emitting phosphors provide a versatile tool for ratio-metric color tuning, enabling a wide color gamut and ensuing applications in information encryption and the anti-counterfeiting area. Here, a double perovskite, Cs₂NaScCl₆:xMn²⁺ single crystals, was grown by a hydrothermal method. Pristine Cs₂NaScCl₆ crystals exhibited a pure blue emission band originating from the self-trapped excitons. Upon doping with Mn²⁺, the crystals exhibited a dual-band emission profile, consisting of both STE and Mn²⁺ emissions. To this end, the ratio of two bands was manipulated with Mn²⁺-doping concentration, rendering a wide color gamut from blue to red. Interestingly, co-doping with Sb³⁺ ions significantly enhanced the overall photoluminescence, boosting the quantum yield from 8.8% to up to 62.4%. Such an enhancement is attributed to an efficient energy transfer process from the STE to Mn²⁺ based on an investigation of photoluminescence lifetime. Importantly, these crystals exhibited an intriguing afterglow after X-ray excitation, with a duration exceeding 3000 s. This remarkable phenomenon opens up many new possibilities for their application in the advanced anti-counterfeiting area.