Electrical spectroscopy methods for the characterization of defects in thin-film compound solar cells

Abstract

The electronic activity of defects and their impact on the efficiency of Cu(In,Ga)Se2 and CdTe solar cells is a subject of continuing interest and dispute in the photovoltaic community. However, after many years of research, the conclusions are far from satisfying yet. Here, the electrical defect spectroscopy results for Cu(In,Ga)Se2 and CdTe absorbers and devices are discussed with focus on findings that have been confirmed on many samples but still do not have a well-grounded interpretation. Charged grain boundaries are proposed as a possible source of some signatures observed in deep level spectra in both materials. Electrical nano-characterization methods combined with standard defect spectroscopy are suggested as a promising solution for unraveling the role and origin of dominating defects for solar cells efficiency.