posted on 2021-05-12, 10:13authored byHan Chen, Sen Ming, Minghao Li, Bin Wang, Jing Su
Lead-free
halide double perovskites A2BB′X6 have
been proposed as potential materials for optoelectronic
application. Among them, Cs2AgBiCl6 exhibits
an indirect band gap in the ultraviolet regime, which is not ideal
for the applications in thin-film photovoltaics. In this work, we
report a strategy to tune the band gap by Sb doping. We perform density
functional theory calculations to investigate the crystal structures
and electronic and optical properties of mixed halide Cs2AgSbxBi1–xCl6 (x = 0, 0.25, 0.5, 0.75, and
1) compounds. Our results show that the crystal structure and symmetry
of these compounds change with the value of x and
that the band gap (HSE) can vary between 2.46 and 3.09 eV depending
on the level of Sb doping. We also find that the spin–orbit
coupling varies quite significantly as the Sb/Bi ratio changes. These
results show that the band gap of Cs2AgBiCl6 can be tuned controllably by chemical adjustment, which is valuable
for its potential optoelectronic application.