PROCESSING OF Cu(In,Ga)Se_2 THIN FILM SOLAR CELLS BY CO-EVAPORATION USING A PHYSICAL VAPOR DEPOSITION SYSTEM WITH EFFUSION CELLS MBE TYPE

摘要

Polycrystalline Cu(In,Ga)Se_2 (CIGS) solar cells are attractive because low cost techniques can be used to obtain high efficiency thin film photovoltaic devices. Several research groups around the globe have developed CIGS/CdS solar cells with efficiencies larger than 15% using evaporation techniques, making it an attractive and reliable technique for thin film deposition. In this work, we are using a PVD system with Knudsen cells MBE type to deposit CIGS thin films on glass/Mo substrates by co-evaporation to obtain CIGS/CdS thin film solar cells. Characterization of co-evaporated CIGS thin films was performed by XRD, SEM and EDS techniques. High quality polycrystalline films were obtained as shown by XRD patterns. SEM micrographs show films having a very uniform appearance with large grain sizes (～1 μm). EDS analysis allowed us verifying that a Cu film could be successfully selenized and converted into Cu_3Se_2, a condition that is necessary to perform the co-evaporation of Cu-In-Ga-Se for obtaining CIGS films. Photoluminescence (PL) studies on CIGS samples with different Ga and Cu concentrations (Ga/Ga＋In ＝ 0.28, 0.34 and 0.35 and Cu/In＋Ga ＝ 0.85, 0.83 and 0.94) have been performed.