Abstract
Lead free halide double perovskites (HDPs) have attracted significant interest of the scientific community owing to their better stability, low cost, and eco-friendly nature, and high power conversion efficiency for optoelectronic, and thermoelectric usages. Herein, the physical properties of two novel Rb2NaInCl6 and Rb2NaTlCl6 HDPs are reported via first principles methods. Both HDPs are found to be stable thermodynamically and geometrically, supported by negative formation enthalpies, and structural optimization. Electronic properties analysis revealed direct band gap values of 4.88 and 3.13 eV for respective Rb2NaInCl6 and Rb2NaTlCl6 structures. Corresponding to these band gap values, both HDPs are optically active in the ultraviolet (UV) region of light. Static dielectric constant (Ɛ1 (0)) is consistent with Penn's model. Maximum polarization is achieved at 7.1/5.16 eV for Rb2Na(In/Tl)Cl6, respectively. Maximum absorption peaks occurred in UV region, predicting their suitability for high energy optoelectronic applications. The optical conductivity revealed the highest intensity of 3049.72 (at 5.4 eV) for Rb2NaTlCl6 and 2632.08 Ω−1cm−1 (at 7.4 eV) for Rb2NaInCl6. Moreover, our analysis of thermoelectric parameters revealed that Rb2NaInCl6 and Rb2NaTlCl6 have figure of merit (ZT) values of 0.73/0.75, respectively. High ZT values and greater absorption in the UV region suggest that Rb2Na(In/Tl)Cl6 are suitable for TE and optoelectronic usages.
Published Version
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