A study of thermal, voltage, and photoinduced effects on the external quantum efficiency of CuInGaSe2 (CIGS) photovoltaic devices

The purpose of this study was to assess the performance of CuInGaSe₂ (CIGS) solar cells ranging from 6.9-11.2% efficiency to identify means of improving device performance. One of the main drivers for this work was to take an independent look at elevated operating temperatures associated with BIPV products like Dow´s POWERHOUSE™ shingle system for performance differences as a function of system operating temperature independent of increasing efficiency to help future product definition. For three of the four samples we observed a clear lack of dark-light current-voltage (JV) superposition and correspondingly via external quantum efficiency (EQE) measurements an electrical field dependent carrier collection response in the blue regime. By inference this performance indicates the presence of impurities in the device, likely in the CdS film that could present an opportunity to further improve the CIGS device performance.