Fig. 5: Excitation and time-resolved photoluminescence properties of halide double perovskites.

a Schematic representation of direct and indirect bandgap semiconductor materials and their expected absorption and excitation spectra. b Normalized absorption and excitation spectra of selected Cs₂AgIn_xBi_1−xCl₆ compounds, where the dotted black line represents the absorption spectra and the solid red line represents the excitation spectra. Excitation spectra were measured by monitoring the emission wavelength at 575 nm. c Time-resolved single-photon counting (TRSPC) measurements for CABC, Bi_0.20In_0.80, Bi_0.15In_0.85, Bi_0.10In_0.90, and CAIC compounds. TRSPC measurements were carried out by exciting the samples at a pulsed-laser wavelength of 402 nm and monitored at an emission wavelength of 500 nm (solid circles represent the photoluminescence decay and the solid black line represents the fitted components). d Time-resolved photoluminescence spectrum of single-crystal Bi_0.10In_0.90 sample at emission wavelength 500 nm.