Performance of Cu(In,Ga)Se2 solar cells under low irradiance

Abstract This study investigates the suitability of using standard Cu(In,Ga)Se 2 cells produced in our laboratories for indoor applications, by describing the irradiance dependence of the parameters of the cells over more then three orders of magnitude. By lowering the irradiance from standard test conditions towards 0.1 mW/cm 2 the performance of the cells is notably reduced, both in terms of efficiency (from 14 to 3%) and V oc (from 630 to 290 mV). This behaviour is due to the low value of the parallel resistance R p of the cells. Simulations on the parameters of the I – V characteristics are carried out showing the influence that the parasitic resistances have at different irradiance levels on the FF of the cells. As a first step in trying to improve the performance of the cells under this particular conditions, we show that the thickness of the ZnO:Al window layer has no influence on the value of the R p , while the thickness of the CdS buffer layer has just a weak influence on it.