Realizing efficient photoluminescence spectral modulation via Sb³⁺/Ln³⁺ co-doping in Cs₂NaInCl₆ double perovskites

The broad-band self-trapped exciton (STE) emission feature of lead-free halide double perovskites makes it challenging to realize emission with various wavelengths in a single material. Cs₂NaInCl₆:Sb³⁺ crystals with blue emission (440 nm) were synthesized by rationally introducing the Sb³⁺ ion into Cs₂NaInCl₆ with a photoluminescence quantum yield (PLQY) up to 99.35%. The Ln³⁺ (Tb³⁺ and Ho³⁺) ions were doped into Cs₂NaInCl₆:Sb³⁺ to achieve spectrally tunable emission from blue to green and pink emission owing to the energy transfer from the host STE to Ln³⁺ ions, with PLQY values of 90.68% and 61.87%, respectively. By carefully adjusting the doping level of Ln³⁺ ions, white light emission with a PLQY of 68.87% was achieved in the Tb³⁺ and Ho³⁺ co-doped Cs₂NaInCl₆:Sb³⁺ system. LED devices based on Sb³⁺/Ln³⁺ co-doped Cs₂NaInCl₆ with multicolor and white light emissions were fabricated based on these phosphors, which exhibit excellent spectral and environmental stability. The results show that double perovskite luminescence materials have potential for application in solid-state lighting and multi-color displays.