Thin-film photovoltaics: What are the reliability issues and where do they occur?

Several aspects of the typical thin-film polycrystalline solar-cell structure can be susceptible to reliability issues. Potential reliability issues for CIGS and CdTe cells are discussed and their probable physical causes are presented. These possible problems include the metallic back contacts, the grain boundaries in polycrystalline materials, the primary cell junctions, the transparent front contacts, and the edges delineating the cells. A general principle is that reliability issues are always localized to specific areas and never spread uniformly over a cell.