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O: Fachverband Oberflächenphysik

O 39: Focussed session: Frontiers of electronic structure theory: Strong correlations from first principles III (jointly with TT)

O 39.10: Vortrag

Mittwoch, 28. März 2012, 12:45–13:00, HE 101

Point defect calculations in CuInSe₂ and CuGaSe₂ using a screened-exchange hybrid functional — •Johan Pohl, Andreas Klein, and Karsten Albe — Institut für Materialwissenschaft, Petersenstr. 32, D-64287 Darmstadt

We present point defect calculations in CuInSe₂ and CuGaSe₂ (CIGS) using the screened-exchange hybrid functional HSE06 with adapted screening. The use of a functional that gives a correct band gap is important for this material, which is used as absorber material in solar cells. The resulting formation enthalpies, charge transition levels and migration barriers of native defects are presented and their implications for solar cell performance are discussed. We focus on the properties of the copper vacancy [1], which is responsible for Fermi-level pinning at the buffer-absorber interface in CIGS solar cells, and the copper interstitial [2], whose fast diffusion has been proposed to play a role for the metastable behaviour of CIGS solar cells. The results for other native antisite and vacancy defects are also presented and discussed. Finally, we compare the different pictures of the defect physics of CIGS obtained by the adapted HSE06 functional versus the local generalized gradient functional in order to point out general issues with local functionals for point defect calculations in semiconductors. [1] J. Pohl, K. Albe, J. Appl. Phys., 108, 023509, (2010). [2] J. Pohl, A. Klein, K. Albe, Phys. Rev. B, 84, 121201(R), (2011).