Synthesis and characterization of Rb2SnBr6: a vacancy-ordered perovskite for efficient optoelectronic devices

Halide double perovskites have garnered significant attention due to their promising structural stability and optoelectronic properties. In this study, we investigate the structural, microstructural, compositional, thermal, optical, and electrical properties of Rb₂SnBr₆, a vacancy-ordered double perovskite, to assess its potential for optoelectronic applications. Powder X-ray diffraction (PXRD) confirms its cubic \(\text{Fm}\overline{3}\text{m }\) phase with a lattice parameter of 10.5781 Å, consistent with previous reports. STEM imaging and EDS analysis further confirm the homogeneous microstructure and elemental composition, supporting the high phase purity of the material. Thermogravimetric analysis (TGA) reveals thermal stability up to 300 ℃, followed by two major decomposition stages at 350–450 ℃ and above 680 ℃, with a stable residual fraction at 900 ℃. Optical characterization via UV–Vis absorption spectroscopy determines a direct bandgap of 2.49 ± 0.02 eV, while Urbach energy analysis yields a value of 0.649 ± 0.001 eV. Photoluminescence (PL) and time-resolved photoluminescence (TRPL) measurements confirm a strong emission in the visible range, with an enhanced intensity under illumination, suggesting a possible positive photoconductivity effect. Raman spectroscopy corroborates the structural integrity of the material under varying light conditions. Impedance spectroscopy (IS) analysis shows a negative temperature coefficient of resistance (NTCR) effect, with increased conductivity under illumination. The conduction mechanism shifts from Quantum Mechanical Tunneling (QMT) in darkness to Correlated Barrier Hopping (CBH) under illumination, further confirming the role of light in charge transport. These findings position Rb₂SnBr₆ as a robust and efficient material for optoelectronic devices, including light-emitting diodes (LEDs) and photonic sensors.