The influence of defects on the cellular open circuit voltage in CuInGaSe2 thin film solar modules—An illuminated lock-in thermography study

•Development of a modified masking method for measuring Voc of single solar cells.•Visualizing defects’ influence on the surrounding solar cell.•Relation between the IR-signal emitted of a defect and respective cell voltage.

CuInGaSe2 (CIGS) thin film solar modules, despite their high efficiency, may contain three different kinds of macroscopic defects referred to as bulk defects, interface defects and interconnect defects. This occurs due to film's sensitivity to inhomogeneities during the manufacturing process. The result is a decrease of electrical power output from a cell or module. In this paper, we present the influence of macroscopic defects on the electrical behavior of CIGS thin film solar cells. To accomplish this, we investigated the relation between the IR-signal emitted of a defect in a cell (measured using illuminated lock-in thermography ILIT) and the respective open circuit cell voltage (Voc,cell) under low light conditions (< 100 W/m²). Furthermore, we developed a modified masking method of measuring Voc,cell of a single cell within a thin film solar module.