Impact of Bi doping on the structural and optical properties of the lead-free double perovskites (Cs2SnCl6:Bi3+) for optoelectronic applications

The lead-free halide-based double perovskites (Cs₂SnCl₆) have gained much attention due to its promising optoelectronic properties, non-toxic nature, and relatively better stability as compared to lead-based perovskites. In the current work, the cost-effective hydrothermal method is employed to synthesize the Bi-doped double perovskite material. Here, systematic incorporation of Bi3+ in Cs₂SnCl₆ nanocrystal is highly essential to improve the optoelectronic properties and modulate the luminescence. Here, Bi3+ is used as a dopant for host-Cs₂SnCl₆ nanocrystal and as-synthesis material preserves its cubic structures up to a certain amount of Sn4+ replacement by Bi3+. Such doped and as-synthesized perovskites are characterized in detail by using photoluminescence (PL), Ultraviolet (UV-Vis) spectroscopy, and X-ray diffraction (XRD). The PL results show that luminescence peaks around 393 nm are shifted towards the higher wavelength (lower energy) after the appropriate doping of Bi in double perovskite. The UV-Vis spectroscopy exhibits the absorption edge of the as-synthesize and Bi-doped perovskites around ~310 nm and a slight shift is observed after Bi incorporation as compared to the as-synthesized one. Also, bandgap of such perovskites lies in the range of 3.28 eV–3.62 eV. The XRD results demonstrate the diffraction peaks of the Cs2SnCl6 double perovskites at 14.55°, 24.27°, and 29.03°, which originated from the planes of (111), (220), (222) respectively. Finally, chromaticity plots (obtained from the PL) confirm the enhancement of blue luminescence due to the Bi-incorporation. Therefore, all the results confirm that highly stable Bi-doped Cs₂SnCl₆ perovskites can be a suitable candidate for fabricating several wavelength-tuneable optoelectronic devices.