Performance comparison of Cu(In,Ga)Se2 solar cells fabricated using RF and DC sputtered ZnO:Al transparent conducting oxides

Abstract

AbstractWe compare the cell efficiency, fill factor and quantum efficiency of Cu(In,Ga)Se2 based solar cells fabricated using two types of transparent conducting oxide (TCO) top layers. In the first case, Cu(In,Ga)Se2 solar cells have been fabricated using the RF sputtered ZnO:Al TCO of the established baseline process. Secondly, while maintaining all other layers the same, DC reactively sputtered ZnO:Al replaced the RF sputtered TCO in the solar cell fabrication process. The DC reactive process was controlled by a plasma emission monitoring (PEM) system. The performance of both cells has been studied. The results show that Cu(In,Ga)Se2 solar cells fabricated using DC sputtered ZnO:Al layers have comparable efficiencies as compared to cells produced using RF sputtered ZnO:Al films. Scanning electron microscopy pictures show that the ZnO:Al layers in both cases have different thickness but similar columnar structure. The highest cell efficiency obtained using the DC and RF sputtered ZnO:Al were 5.6% and 5.5% respectively. The fill factor and maximum quantum efficiency for Cu(In,Ga)Se2 solar cells fabricated using DC sputtered ZnO:Al layers were 50.5% and 86% respectively. Cu(In,Ga)Se2 solar cells made‐up using RF sputtered ZnO:Al layers had the fill factor of 46.2% and the maximum quantum efficiency of 83%. The Cu(In,Ga)Se2 absorber layers used in the fabrication of these cells were not representing the best absorber layers produced by the Angstrom solar centre. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)