Ab-Initio Study of Defect Physics for Layered LaCuChO and BaCuChF (Ch=\{S,Se,Te\}) Structures

Layered oxychalcogenides LnCuChO (Ln = \{La,Pr,Nd\}, Ch = \{S,Se,Te\}) and isostructural layered fluorochalcogenides BaCuChF have drawn much interest in recent years as p-type wide bandgap semiconductors with applications in transparent electronics and photovoltaics. Previous experimental and computational studies concluded for both LaCuChO, with a bandgaps between 2.4-3.1 eV, and BaCuChF, with optical bandgaps between 2.8-3.5 eV, that p-type conductivity is primarily due to copper vacancies. We report a comparative {\it{ab-initio}} computational study of the defect physics for both families of materials. Point defects and defect complexes are taken into account and previously omitted corrections have been included.\footnote{A. Zakutayev, J. Tate, G. Schneider. \emph{Phys. Rev. B.} \textbf{82}, 195204, (2010)}$^,$\footnote{H. Hiramatsu, T. Kamiya, T. Tohei, E. Ikenaga, T. Mizoguchi, Y. Ikuhara, K. Kobayashi, H. Hosono. \emph{J. Am. Chem. Soc.} \textbf{132}, 15060, (2010)} Accurate chemical potential stability diagrams and formation energies are calculated using the GGA+U method and fitted elemental-phase reference energies.\footnote{V. Stevanovic, S. Lany, X. Zhang, A. Zunger. \emph{Phys. Rev. B.} \textbf{85}, 115104, (2012)}