DEVIATIONS FROM STOICHIOMETRY AND MOLECULARITY IN THE SOLAR CELL MATERIAL CuInS2

The chalcopyrite group of semiconductors is known to represent attractive materials for achieving more efficient and low-cost solar cells. From this group of materials the CuInS2 (CIS) is intensively investigated as p-type absorber layer in 3D solar cell concepts. An important issue in studies focusing on improvements of solar cell efficiencies is related to the defect chemistry of CIS. Based on theoretical and experimental studies several aspects of the defect chemistry of CuInS2 are discussed. The anti-site point defects, which form the Cu-Au ordered structure are studied in samples of pure, Cu-rich, In-rich, and cation doped CIS. Cu-Au ordering was identified via Raman spectroscopy and XRD studies on pure and doped CuInS2 with a deviation from molecularity