Distortions observed in current-voltage characteristics of photovoltaic solar cells

Different types of undesirable distortions appear during final assessment of the performance of photovoltaic solar cells. It is essential to understand the reasons behind these features in order to avoid them in final current-voltage characteristics. Recent experimental results on GaAs-based solar cells and the results reported in the literature on CuInGaSe2 (CIGS) and CdTe solar cells have been taken as examples to explore the reasons behind these behaviours. Critical analysis of these results shows that the "roll-over" effects and "cross-over" effects between the dark I-V and light I-V curves could appear due to the existence of non-ideal metal/insulator/semiconductor (MIS)-type front electrical contacts in photovoltaic solar cells. This is in addition to the well-known case of the presence of back contact barrier. The methods to avoid these undesirable features are proposed and discussed.