Tunable Efficient White Emission in Holmium Doped Double Perovskites Cs₂KInCl₆ via Antimony Sensitization

Abstract Recently, ns² metal ions (such as Bi³⁺ and Sb³⁺) doped double perovskites have captured intense attention for their efficient emission, however, achieving efficient and tunable white light emission is always an enormous challenge. Herein, Sb³⁺/Ho³⁺ co‐doped Cs₂KInCl₆ double perovskites are proposed, and the photoluminescence results show that there are two emission bands, one broad cyan emission band stems from self‐trapped exciton (STE) in [SbCl₆]^3‐ octahedron, while another red emission band derives from the f‐f transitions of Ho³⁺. The emission processes for Sb³⁺/Ho³⁺ co‐doped Cs₂KInCl₆ show that Sb³⁺ can act as the sensitizer to activate Ho³⁺ emission, which is due to the energy transfer channel from STE to Ho³⁺. As the Ho³⁺ concentration increases, the luminous color of Sb³⁺/Ho³⁺ co‐doped Cs₂KInCl₆ can be modulated from cyan to orange under 315 nm light irradiation, and the white emission can even be obtained with a photoluminescence quantum yield of 90 ± 2% when the energy‐transfer efficiency is 50%. Finally, single compound white‐light emitting diodes and fluorescent anti‐counterfeiting labels based on 0.5%Sb³⁺/60%Ho³⁺ co‐doped Cs₂KInCl₆ are fabricated. This work provides an effective strategy to achieve efficient tunable white emission in lead‐free double perovskites through ns² metal and lanthanide ion co‐doping.