Cu2SiSe3 as a promising solar absorber: harnessing cation dissimilarity to avoid killer antisites

Copper-chalcogenides are promising candidates for thin film photovoltaics due to their ideal electronic
structure and potential for defect tolerance. To this end, we have theoretically investigated the
optoelectronic properties of Cu2SiSe3, due to its simple ternary composition, and the favorable
difference in charge and size between the cation species, limiting antisite defects and cation disorder.
We find it to have an ideal, direct bandgap of 1.52 eV and a maximum efficiency of 30% for a 1.5
μm-thick film at the radiative limit. Using hybrid density functional theory, the formation energies
of all intrinsic defects are calculated, revealing the p-type copper vacancy as the dominant defect
species, which forms a perturbed host state. Overall, defect concentrations are predicted to be low
and have limited impact on non-radiative recombination, as a consequence of the p − d coupling and
antibonding character at the valence band maxima. Therefore, we propose that Cu2SiSe3 should be
investigated further as a potential defect-tolerant photovoltaic absorber.

Preprint: 10.26434/chemrxiv-2023-7454p