Unveiling the dual-channel energy transfer mechanism and enhanced luminescence in Ag+/Er3+ co-doped Cs2NaBiCl6 double perovskites

A dual-channel energy transfer in Ag + /Er 3+ co-doped Cs 2 NaBiCl 6 was revealed. • The energy transfer from STE to Er 3+ is a phonon-assisted cooperative foster energy transfer. • White LEDs with a single Ag + /Er 3+ co-doped Cs 2 NaBiCl 6 phosphors were achieved. Herein, the photoluminescence of hydrothermally synthesized Cs 2 NaBiCl 6 is controlled by Ag + and Er 3+ co-doping, and a dual-channel ET mechanism is proposed. When doped with Ag + , the photoluminescence of Cs 2 NaBiCl 6 increases by as much as 24.7 times. We have discovered that Ag + can reduce the band gap width, break the parity symmetry of the transition, and significantly enhance the strength of STE. Futher, new luminescence center was introduced in Ag + /Er 3+ co-doped Cs 2 NaBiCl 6 . Femtosecond transient absorption (fs-TA) spectroscopy data indicate that there exists a dual-channel ET process from (Ⅰ) the host to Er 3+ and from (Ⅱ) the host to the self-trapping exciton state and then back to Er 3+ . As the bridge of ET, Ag + alters the local symmetry of the Er 3+ site, significantly facilitating the energy transfer from STE to Er 3+ , and increasing the probability of Er 3+ radiation recombination. Futhermore, white LEDs with a single host phosphors have been achieved. Download: Download high-res image (145KB) Download: Download full-size image To address the problem of low photoluminescence efficiency in double perovskite materials, Ag + and Er 3+ were doped into Cs 2 NaBiCl 6 to enhance luminescence. Doping with Ag + increased the photoluminescence of Cs 2 NaBiCl 6 by 24.7 times. The energy transfer mechanisms among ns 2 metals, transition metals, and rare earth ions were investigated, and a dual-channel energy transfer mechanism was proposed. Furthermore, white LEDs using a single phosphor have been achieved, with color coordinates of (0.327, 0.338). This work provides a new perspective for designing novel double perovskites to realize unique dual-channel energy transfer and white LEDs.