Photoluminescence enhancement study in a Bi-doped Cs 2 AgInCl 6 double perovskite by pressure and temperature-dependent self-trapped exciton emission.

Here, we report a halide precursor acid precipitation method to synthesize Cs 2 AgIn 1- x Bi x Cl 6 ( x = 0, 0.02, 0.04, 0.08, 0.16, 0.32, 0.64, and 1) microcrystals. Cs 2 AgInCl 6 and Bi derivative double perovskites show broadband white light emission via self-trapped excitons (STEs) and have achieved the highest internal quantum efficiency of up to 52.4% at x = 0.08. Synchrotron X-ray diffraction confirmed the linear increase of lattice parameters and cell volume with Bi 3+ substitution at In 3+ sites. Absorbance, photocurrent excitation, and photoluminescence excitation spectra are used to observe possible transitions from the valence to the conduction band or free exciton (FE) states as well as transitions within local Bi 3+ states. The broadband photoluminescence is quenched via a single nonradiative process with an activation energy Δ E = 1490 cm -1 for Cs 2 AgIn 0.92 Bi 0.08 Cl 6 . Under normal conditions, we observed STE emission, but applying external pressure alters the electronic structure such that at elevated pressure, the only emission via the FE state is observed. We anticipate that structure, temperature and pressure-dependent photoluminescence studies will help the future use of a single-source lead-free double perovskite for white light-emitting diode applications.