• Rodriguez-Alvarez, H.; Mainz, R.; Scheer, R.; Schock, H.-W.: Reaction paths during the sulfurization of In/Cu-Ga and Cu-In-Ga thin films for the fabrication of Cu(In,Ga)S2 at different heating rates. In: De Santi, G.F. [u.a.] [Eds.] : 25th European Photovoltaic Solar Energy Conference and Exhibition / 5th World Conference on Photovoltaic Energy Conversion, 6-10 September 2010, Valencia, Spain. EU PVSECMunich: WIP, 2010. - ISBN 3-936338-26-4, p. 3406-3410


Abstract:
The purpose of this work is to investigate the reaction paths during the sulfurization of two types of metallic precursors, In/Cu-Ga bilayers and Cu-In-Ga single layers. The metallic precursors were sulfurized in a closed volume at three constant heating rates: 14 Kmin-1, 28 Kmin-1 and 56 Kmin-1. We use synchrotron-based polychromatic X-ray diffraction to monitor in real time the formation of the Cu(In,Ga)S2 thin films. The sequence of solid phases before the formation of the chalcopyrite phase, and the temperatures of the phase transitions depend on the heating rate and on the metallic precursor. As for the In/Cu-Ga bilayers, we found that increasing the heating rates shifts the onset of the sulfurization to higher temperatures. Decreasing the heating rate favors the formation of CuS and Cu-Ga intermetallic phases. As for the Cu-In-Ga single layers, we found a significant composition-caused strain of the Cux(In,Ga)y phases during the sulfurization. Furthermore, the Cu(In,Ga)S2 thin films fabricated from these single-layered precursors presented a bad adhesion to the Mo back contact. We developed a one-step rapid thermal process (RTP) where suitable Cu(In,Ga)S2 thin films for solar cells were obtained.