Exploring the optoelectronic properties of novel lead-free double halide perovskites Cs₂NaInX₆ (X = Br, Cl, I) for photovoltaic applications: DFT study

Materials science is crucially involved in researching advanced materials for energy conversion and storage. The discovery process has been accelerated by computational simulations, which have become a powerful tool for predicting the properties of new materials in recent years. This study examines the structural, electronic, and optical properties of double perovskites Cs₂NaInX₆ (X = Br, Cl, and I), emphasizing their potential use in energy conversion. Relevant results for optoelectronic applications have been obtained through a comparative study of the studied halide double perovskites. The compounds exhibit a high absorption coefficient of over 10⁶ cm⁻¹ in the ultraviolet, as demonstrated by the obtained results. In addition, these compounds are able to absorb light with a maximum absorption of 10⁵ cm⁻¹ in the visible range. Cs₂NaInX₆ double perovskite compounds exhibit direct semiconductor behavior with optical bandgap energy values of around 2.46, 3.44, and 1.64 eV for Cs₂NaInBr₆, Cs₂NaInCl₆, and Cs₂NaInI₆, respectively. The reached results led to the conclusion that Cs₂NaInX₆ compounds can be used as a promising candidate for optoelectronic and solar cell applications. Our understanding is that this is the first theoretical prediction of the electro-optical properties of these compounds that has not yet been confirmed experimentally.