Paper detail

Behavior of $\mathbf{Σ3}$ grain boundaries in \CISe\ and \CGSe\ photovoltaic absorbers as revealed by first-principles hybrid functional calculations

The inconclusive results of the previous first-principles studies on the \S3 \ grain boundaries (GBs) in \CISe\ reveal the importance of employing a method that can correctly describe the electronic structure of this solar-cell material. We have employed hybrid functional calculations to study the \S3 (112) and \S3 (114) GBs in \CISe\ and \CGSe. The electronic structure changes introduced by the formation of GBs are threefold: creation of gap states, shift in band edges, and alteration of bandgap sizes. Gap states commonly behave as recombination centers, but the band alignment and the change in the bandgap size induced by GBs mitigate the destructive effect of these states in \CISe. That means, \S3 \ GBs are not detrimental for the carrier transport in devices based on \CISe. Conversely, these GBs are destructive for the carrier transport in \CGSe. The different behaviors of the \S3 \ GBs in CISe and CGSe might be considered by experimentalists to optimize the device fabrication to achieve high-performance solar cells.