Influence of Na and Cu on the thermodynamic stability and electronic band alignment of the In2S3/ Cu(In,Ga)(Se, S)2 thin-film solar cell interface

CdS is a well-established buffer layer for Cu(ln,Ga)(S,Se)
₂
(CIGS)-based thin film solar cells. However, because of its toxicity, low quantum efficiency at blue-wavelength region, and the drawbacks of the chemical bath deposition technique used for its growth, looking for an alternative buffer material has been a matter of debate in recent years. In this context, β-In
₂
S
₃
is considered as a promising substitution for CdS. In this contribution, we study-by means of hybrid density functional theory-incorporation of Na and Cu impurities in In2S3 and investigate their impact on the thermodynamic stability of In2S3. Furthermore, to understand how band lineups would affect the performance of the cells buffered with In
₂
S
₃
, we present calculations of band alignments of pure and chemically modified In
₂
S
₃
with various chalcopyrites.