Developing an efficient energy transfer host for the controllable doping of Ho3+ in Cs2NaLuCl6 via Ag+/Bi3+ co-doping

Currently, lanthanide (Ln 3+ ) doped double perovskites (DPs) suffer from poor controllability of doping and the high concentration quenching phenomenon. Herein, a novel efficient energy transfer (ET) host of Cs 2 NaLuCl 6 Rare-earth-based (RE-based) DPs via Ag + /Bi 3+ co-doping for further Ho 3+ doping is developed. Benefiting from Ag + /Bi 3+ - manipulated the parity of the wavefunction of the self-trapped exciton, intense self-trapped excitons (STEs) broadband warm white visible emission is boosted. Specifically, photoluminescence quantum yield (PLQY) of co-doping with Bi 3+ and Ag  +  ions in Cs 2 NaLuCl 6 under 350 nm excitation is dramatically promoted to 86.19 % with half maximum (FWHM) of 224 nm. Although the pristine crystal Cs 2 NaLuCl 6 exhibits intrinsic blue emission with FWHM of 75 nm. Furthermore, the ET channel from STEs to Ho 3+ was constructed by tri-doping Ho 3+ , and the effective red and near-infrared (NIR) emission of Ho 3+ was obtained. Finally, NIR light-emitting diodes (LEDs) and white LED based on Ho 3+ doped/undoped Cs 2 Na 0.8 Ag 0.2 Lu 0.98 Bi 0.02 Cl 6 DPs were prepared with different application features. Specifically, white LEDs showed higher color rendering index and lower associated color temperature, while NIR LEDs showed good night vision imaging. This work provides a new strategy for the design of an ET host suitable for Ln 3+ doping, avoiding the effects of the concentration quenching phenomenon that always occurs in heavily doped hosts and realizing controllable doping.