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

Recently, ns(2) 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 ns(2) metal and lanthanide ion co-doping.