Improving the Optical and Thermoelectric Properties of Cs2InAgCl6 with Substitutional Doping: A DFT Insight

TL;DR

This study uses first-principles calculations to demonstrate that substitutional doping can significantly reduce the band gap of Cs2InAgCl6, enhancing its optoelectronic and thermoelectric properties for photovoltaic applications.

Contribution

It provides a detailed DFT analysis showing how specific dopants modify the electronic structure and improve thermoelectric performance of Cs2InAgCl6.

Findings

Band gap reduced from 3.3 eV to 0.6 eV with doping.

Enhanced power factor (up to 2.03 mW/mK2) in Pb-doped case.

Strong absorption peak near Shockley-Queisser limit in co-doped material.

Abstract

New generation Indium based lead-free Cs2InAgCl6 is a promising halide material in photovoltaic applications due to its good air stability and non-toxic behavior. But its wide band gap (>3 eV) is not suitable for solar spectrum and hence reducing the photoelectronic efficiency for device applications. Here we report a significant band gap reduction from 3.3 eV to 0.6 eV by substitutional doping and its effect on opto-electronic and opto-thermoelectric properties from first-principles study. The results predict that Sn/Pb and Ga & Cu co-doping enhance the density of states significantly near the valence band maximum (VBM) and thus reduce the band gap by shifting the VBM upward while the alkali-metals (K/Rb) slightly increase the band gap. A strong absorption peak near Shockley-Queisser limit is observed in co-doped case while in Sn/Pb-doped case, we notice a peak in the middle of the visible region of solar spectrum. The nature of band gap is indirect with Cu-Ga/Pb/Sn doping with a significant reduction in the band gap. We observe a significant increase in the power factor (PF) (2.03 mW/mK2) for n-type carrier in Pb-dpoing, which is ~3.5 times higher than the pristine case (0.6 mW/mK2) at 500 K.