Efficient red photoluminescence in holmium-doped Cs2NaInCl6 double perovskite

Metal halide perovskites with efficient and stable self-trapped exciton emission have attracted considerable attention for next-generation solid-state lighting owing to their ultrabroadband emission. However, it remains challenging to widen the color gamut and realize high color-rendering index due to the lack of highly saturated red color-emitting inorganic lead-free perovskite materials with narrow full width at half-maximum. Here, we report a lanthanide-codoped system (Cs2NaInCl6:Sb3+/Ho3+) that enables efficient blue and red emissions with photoluminescence quantum yields of up to 99% and 72%, respectively. The energy transfer efficiency in Ho3+-doped Cs2NaInCl6:Sb is up to 73%, which can overcome the weak absorption cross-section of the f-f transition of lanthanide ion and improve its luminescence performance. Benefitting from the efficient energy-transfer channel from the self-trapped excitons to Ho3+, the emission color is continuously tuned from blue to red by controlling the Ho3+-doping concentration.