Experimental determination of physical parameters in CIGS solar cells

Thin-film Cu(In,Ga)Se2 (CIGS) and CdTe photovoltaic (PV) modules have the potential to become competitive to silicon PV modules both in terms of their performance as well as productions costs. However, despite of many years of investigating them, some physical processes are not well-understood yet. One of the tools which may help to discover some of these process are numerical simulations with use of equivalent diode model applied for the analysis of physical behaviour of solar cells. In the paper results of experimentally determined values of diffusion and recombination related components of diode dark saturation corresponding to double-diode model (DEM) are presented. Obtained values result from considering of p-n junction physical basics as well from numerical simulations. To fit large amount of I-V curves to one of the commonly used diode models special PC program has been developed. Its role is fast and efficient importing of I-V curves from database, immediate performing fitting procedure with subsequent storing and graphical presentation of the calculated results. Presented examples show a discrepancy between diffusion and recombination dark current components derived using both methods. The reason for this discrepancy is discussed.