Siemens Solar CIS Photovoltaic Module and System Performance at the National Renewable Energy Laboratory

This paper evaluates the individual module and array performance of Siemens Solar Industries' copper indium diselenide (CIS) polycrystalline thin-film technology. This is accomplished by studying module and array performance over time. Preliminary temperature coefficients for maximum power, maximum-power voltage, maximum-power current, open-circuit voltage, short-circuit current, and fill factorare determined at both the module and array level. These coefficients are used to correct module/array performance to 25 degrees Celsius to evaluate stability. We show that CIS exhibits a strong inverse correlation between array power and back-of-module temperature. This is due mainly to the narrow bandgap of the CIS material, which results in a strong inverse correlation between voltage andtemperature. We also show that the temperature corrected module and array performance has been relatively stable over the evaluation interval (2 years).