Effects of buffer layers on SSI CIGSS-absorber transient I-V and C-V behavior

Many thin-film CIS photovoltaic devices exhibit a modest level of reversible transient behavior in electrical properties. This paper evaluates this behavior by comparing three cell configurations processed differently. The configurations include CIGSS cells made by Siemens Solar Industries (SSI), SSI absorbers plus buffers/windows done elsewhere, and standard NREL CIGS cells. The buffers used include combinations of the following: KCN solution etching treatment, annealing of the samples after CdS deposition, and/or chemical vapor deposition of ZnO without CdS deposition. All cells made with SSI absorbers showed transient behavior in fill factor, while the NREL cells did not. Post-annealing of devices was found to improve baseline performance and reduce transient behavior.