Insights into RbSrX3 (X= Cl, Br, I) Halide Perovskites: First-Principles Study on their Potential for Optoelectronic and Thermoelectric Applications

This study theoretically investigates the properties of RbSrX3 halide perovskites to advance their technological applications, focusing on thermoelectric, mechanical and optoelectronic characteristics via first-principles calculations. Structural stability at the ground state was confirmed using equation of state of Birch–Murnaghan and further by formation energy and tolerance factor. The structural analysis reveals a systematic increase in lattice parameters and unit cell volumes with the substitution of larger halide ions, consistent with ionic size effects. Analysis of electronic spectra show that RbSrCl3, RbSrBr3, and RbSrI3 exhibit indirect bandgaps of 7.68, 6.52, and 4.96 eV, respectively, which increase to 9.50, 8.09, and 6.21 eV with the inclusion of spin-orbit coupling, indicating their potential in ultraviolet (UV) photodetectors, insulating optical coatings. Mechanical analysis show their stability, anisotropy and ductile behavior. Optical properties analysis, including refractive index, optical conductivity, dielectric constants and absorption characteristics, suggests that these compounds are well-suited for optoelectronic and UV sensor technologies. Using BoltzTrap code, the transport properties were evaluated, showing n-type conductivity due to negative Seebeck coefficients. The calculated thermoelectric efficiency (ZT) scores attained 1.25, 0.76, and 0.57 under a temperature of 950 K, indicating significant thermoelectric performance. This work identifies RbSrX3 and related materials as strong contenders for use in UV photodetectors, insulating optical coatings, radiation-resistant optoelectronic systems, and potential use in high-temperature thermoelectric devices, providing a foundation for future experimental studies.