First-Principles Modeling of Point Defects and Complexes in Thin-Film Solar-Cell Absorber CuInSe2

Abstract

Point defects and complexes may affect significantly physical, optical, and electrical properties of semiconductors. The Cu(In,Ga)Se2 (CIGSe) alloy is an absorber material for low-cost thin-film solar cells. Several recently published computational investigations show contradicting results for important point defects such as copper antisite substituting indium (CuIn), indium vacancy (VIn), and complexes of point defects in CuInSe2. In the present work we study effects of the most important computational parameters especially on the formation energies of point defects. Moreover, related to defect identification by the help of their calculated properties we discuss possible explanations for the three acceptors, which occur in photoluminescence measurements of Cu-rich samples. [S. Siebentritt et al., Progress in Photovoltaics: Research and Applications 2010, 18, 390, S. Siebentritt et al., Physica Status Solidi (c) 2004, 1, 2304.] Finally, new insight into comparison between theoretical and experimental results is presented in the case of varying chemical potentials and of formation of secondary phases.