Theoretical investigations of double perovskites Rb2YCuX6 (X =Cl, F) for green energy applications: DFT study

• Published in: The Journal of physics and chemistry of solids 2024-10, Vol.193, p.112171, Article 112171
• Main Authors: Rahman, Nasir, Husain, Mudasser, Azzouz-Rached, Ahmed, Al-Ammar, Essam A., Sfina, Nourreddine, Alawaideh, Yazen M., Abualnaja, Khamael M, Alosaimi, Ghaida, Hamza, REKAB-DJABRI, Samreen, Ayesha, Belhachi, Soufyane, Algethami, Norah, Althobaiti, Hanan A., Rashid, Amin Ur
• Format: Article
• Language: English
• Subjects: Double perovskites; Elastic properties; Electronic; First principle study; Optical; Structural; Tb-mBj; Wien2K
• ISSN: 0022-3697; 1879-2553
• DOI: 10.1016/j.jpcs.2024.112171

Double perovskites, which have remarkable performance, great stability, environmental friendliness, and are Pb-free, are emerging materials for solar cells and thermoelectric generators. Herein, we present density functional theory (DFT) calculations on novel metal Pb-free double halide perovskites, Rb2YCuX6 (X = Cl, F), aiming to explore their potential for renewable energy applications. The compounds' negative formation energy confirms their thermodynamic stability, the Goldsmith tolerance factor (tG) provides evidence for their structural stability in the cubic crystalline form and the stable phonon dispersion spectrum confirm its dynamic stability. We found that the lattice constant increases noticeably as the halogen anions change (i.e replacing F by Cl). The mechanical stability of the compounds is validated by the relationships between elastic constants (ECs), namely C11–C12 > 0, C11 > 0, C11 + 2C12 > 0, and B > 0. Utilizing the TB-mBJ potential, it has been determined that the compound Rb2YCuCl6 exhibits an indirect bandgap semiconducting nature with a band gap of 2.31 eV. On the other hand, the compound Rb2YCuF6 demonstrates properties of a direct bandgap semiconductor with a band gap of 2.47 eV. In order to evaluate their suitability for applications in solar cells and optoelectronic devices, we analyze the dielectric function (ε(ω)), optical conductivity (σ(ω)), and reflectivity (R(ω)) of the compounds. Moreover, the thermoelectric performance has been elucidated through the analysis of the power factor (PF) and figure of merit (ZT). The presence of ultralow lattice thermal conductivity and a significant Seebeck coefficient (S) further enhance ZT, making these compounds suitable for thermoelectric applications. Our findings provide comprehensive insight in exploring the properties of Pb-free Rb2YCuX6 (X = Cl, F) double perovskites. It confirms their stability, suitable bandgaps, and impressive thermoelectric properties, highlighting their potential for solar cells and thermoelectric generators as environmentally friendly and sustainable energy solutions. •The study focuses on Rb2YCuX6 (X = Cl, F) double halide perovskites, analyzed using density functional theory (DFT).•Thermodynamically stable and confirm structural stability in the cubic crystalline form.•Mechanically stable.•Rb2YCuCl6: Indirect bandgap semiconductor with a bandgap of 2.31 eV.•Rb2YCuF6: Direct bandgap semiconductor with a bandgap of 2.47 eV.