Comprehensive characterization of Cu-rich Cu(In,Ga)Se2 absorbers prepared by one-step sputtering process

The characteristics of the Cu-rich Cu(In,Ga)Se-2 (CIGS) films prepared by one-step sputtering process from a single quaternary target have been studied. The influences of working pressure, substrate temperature, Mo back contact, and KCN treatment on the properties of CIGS films were investigated. Target stability has been in-situ monitored by using optical emission spectroscopy. Obvious compositional change due to the KCN effect was observed, while only slight variation was caused by working pressure. We found the preferred orientation and crystallinity of one-step sputtered CIGS films were affected by the working pressure and substrate temperature when CIGS were directly deposited on the glass substrates. However, for the device fabrication, Mo back contacts dominated the growth behavior of CIGS films and induced better crystallinity with larger CIGS grain sizes. To explore the electrical properties of CIGS films on Mo back contacts, we developed a simple two-point probe measurement to examine the conductive channels within CIGS films before the device fabrication. Finally, one-step sputtered CIGS devices showed the efficiency of more than 8% at the working pressure of 0.4-2.7 Pa with KCN treatment. (C) 2012 Elsevier B.V. All rights reserved.