Viability of Cs₂AgBiCl₆: Cr³⁺/Yb³⁺ and Cs₂AgInCl₆: Cr³⁺/Yb³⁺ as Efficient Photoluminescent Materials and Other Photophysical Applications

Lead-free, pure inorganic halide double perovskites (HDPs) have emerged as promising materials in optoelectronic applications due to their enhanced structural stability and excellent optical efficiency. Introducing d- and f-elements to the class of HDPs not only provides a chemically, structurally, and electronically diverse pool of materials but also results in improved physical and chemical properties and applications. In this study, we report Cr3+ and Yb3+ substitution at the M site in Cs2AgMCl6 HDPs (M = Bi and In) to verify their impact on the structural and optical properties of HDPs. The structural changes induced by the incorporation of transition-metal and rare-earth metal elements were investigated by X-ray diffraction, TGA, and EPR studies, whereas a detailed optical analysis was performed by UV–vis and PL spectroscopy measurements. However, a giant superlinear power dependence of photocurrent was observed in these HDPs, enabling their broadening applications in photophysics.