Interfacial alloying and defect formation inside operational cigs solar cells

Nanoscale depth-resolved and cross sectional cathodoluminescence spectroscopy (DRCLS) provides correlations of local electronic and chemical structure with actual solar cell performance in sets of copper indium gallium diselenide (CIGS)/CdS/ZnO/ITO thin film solar cells. Local cross sectional and depth-dependent results throughout the various layers within the solar cells reveal local spatial variations in the CIGS band structure, even within the same grain. Band structure correlations to the efficiency, open circuit voltage, short circuit current performance characteristics of individual solar cells show evidence for alloying or intermixing between the CdS and ZnO layers forming alloys with higher band gap energies and degraded performance. Also, higher ZnO/ITO band edge intensities correspond to higher short circuit currents.