ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Band gap engineering and thermoelectric energy conversion in Li₂InCuX₆ (X = Cl, F) Double Perovskites

Mounir Abbad, Rafik Souiah, Ahmed Azzouz-Rached, Wafa S. Aljuaid, Eman M. Alshehri, Hind Albalawi, Saleha Qissi, Essam A. Al-Ammar, Vineet Tirth, and Nasir Rahman

Faculty of Sciences, Morsli Abdallah University of Tipaza, Tipaza, Algeria

E-mail: nasir@ulm.edu.pk

Received: 25 February 2026  Accepted: 19 May 2026

Abstract:

This study presents a comprehensive first-principles investigation of the structural, electronic, optical, and thermoelectric properties of lead-free double perovskites Li₂InCuX₆ (X = Cl, F) using the FP-LAPW method. Structural and phonon analyses confirm the thermodynamic and dynamical stability of both compounds. The mBJ-based electronic calculations reveal direct band gaps of 0.774 eV (Cl) and 1.153 eV (F), indicating their suitability for optoelectronic applications. Halide substitution significantly influences bonding strength, resulting in enhanced mechanical rigidity and thermal stability in Li₂InCuF₆. Optical analysis shows strong absorption in the visible–UV region, while thermoelectric calculations demonstrate promising performance with maximum ZT values approaching 0.80 at high temperatures. Li₂InCuCl₆ exhibits a higher power factor, whereas Li₂InCuF₆ benefits from lower thermal conductivity and superior high-temperature efficiency. These results highlight the effectiveness of halide engineering in tuning multifunctional properties for energy harvesting and optoelectronic applications.

Keywords: Lead-free double perovskites; Density functional theory (DFT); FP-LAPW method; Optoelectronic properties; Thermoelectric materials; Halide engineering; Energy harvesting

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-026-05085-w

Chemical Papers 80 (10) 11701–11716 (2026)