Universal statistics of parasitic shunt formation in solar cells, and its implications for cell to module efficiency gap

Parasitic shunt formation is an important cause of variability and module efficiency loss in all photovoltaic technologies. In this letter, we quantify the nature of this shunt variability in four major thin film photovoltaic (TFPV) technologies, namely, amorphous silicon (a-Si:H), organic (OPV), Cu(In,Ga)SSe (CIGS), and CdTe. We analyze a wide variety of datasets to show that the shunt current exhibits a robust universal log-normal behavior for all these technologies. We affirm this conclusion by rigorous statistical analysis of the available data. We use equivalent circuit simulations to quantitatively illustrate the importance of this heavy-tailed distribution towards determining the universal gap between cell and module efficiency.