CIGS Thin Film Solar Cell Prepared by Reactive Co-sputtering

摘要

The reactive co-sputtering was developed as a new way of preparing high quality CuInGaSe_2(CIGS) films from two sets of targets; Cu_(0.6)Ga_(0.4) and Cu_(0.4)Ga_(0.6) alloy and Cu and (In_(0.7)Ga_(0.3))_2Se_3 compound targets. During sputtering, Cu, In, Ga metallic elements as well as the compound materials were reacted to form CIGS simultaneously in highly reactive elemental Se atmosphere generated by a thermal cracker. CIGS layer had been grown on Mo/soda-lime glass(SLG) at 500℃. For both sets of targets, we controlled the composition of CIGS thin film by changing the RF power for target components. All the films showed a preferential (112) orientation as observed from X-ray diffraction analysis. The composition ratios of CIGS were easily set to 0.71-0.95, 0.10-0.30 for [Cu]/[Ⅲ] and [Ga]/[Ⅲ], respectively. The grain size and the surface roughness of a CIGS film increased as the [Cu]/[Ⅲ] ratios increased. The solar cells were fabricated using a standard base line process in the device structure of grid/ITO/i-ZnO/CdS/CIGS/Mo/ SLG. The best performance was obtained the performance of V_(oc) = 0.45 V, J_(sc) =35.6, FF= 0.535, η= 8.6% with a 0.9 μm-CIGS solar cell from alloy targets while V_(oc) = 0.54 V, J_(se) =30.8, FF= 0.509, η = 8.5% with a 0.8 μm-CIGS solar cell from Cu and (In_(0.7)Ga_(0.3)_2Se_3.