Electrical Characterization of Defects in Cu-Rich Grown CuInSe$_{\text{2}}$ Solar Cells

We study defects in CuInSe2 (CIS) grown under Cu-excess. Samples with different Cu/In and Se/metals flux ratios were characterized by thermal admittance spectroscopy, capacitance-voltage (C-V) measurements, and temperature-dependent current-voltage (IVT) measurements. All samples showed two different capacitance responses, which we attribute to defects with energies around 100 and 220 meV, plus the beginning of an additional step that we attribute to a freeze-out effect. By application of the Meyer-Neldel rule, the parameters of the two defects can be assigned to two different groups, both lying within the energy region of the so-called N1-defect that has been observed for Cu-poor absorbers.