First principle analysis of lead-free variant perovskites iodides for optical and thermoelectric applications

The Cesium-based variant perovskites are emerging aspirants for optoelectronic and thermoelectric applications. We have comprehensively studied and executed calculations for the analysis of optical and transport characteristics of new family of variant perovskites Cs2XI6 (X = Ti, Zr, Hf). The structural stability has been confirmed by Goldsmith tolerance factor. Energy band gap calculations revealed a direct band gap for the studied materials, that increases from 1.41 eV to 2.35 eV and 2.92 eV by the replacement of Ti by Zr and Hf. The maximum absorption is found to move from visible to ultraviolet region by replacement of Zr and Hf. This ensures their importance for solar cells. Also, the transport characteristics are evaluated for temperature 0-400 K and chemical potential from -0.15 eV to 0.25 eV. The high thermoelectric efficiency has been reported for Cs2HfI6 from the studied compounds. (C) 2021 The Author(s). Published by Elsevier B.V.