Structural and electrical properties of co-evaporated Cu(In,Ga)Se2 thin films with varied Cu contents

Abstract

Cu(In,Ga)Se2 (CIGS) thin films were fabricated with varying Cu contents. Cu/(Ga+In) ratios were varied between 0.4 and 1.02. Solar cells were then fabricated by co-evaporation using the CIGS layers as absorbers. The influences of Cu content on the cells' structural, optical and electrical properties were studied. The CIGS thin films were characterized by X-ray diffractometer, scanning electron microscopy, energy-dispersive spectroscopy, four-point probe measurement and Hall measurement. Grain size in the films increased with increasing Cu content. At a Cu/(Ga+In) ratio of 0.86, the (220/204) peak was stronger than the (112) peak and carrier concentration was 1.49×1016cm−3. Optimizing the Cu content resulted in a CIGS solar cell with an efficiency of 16.5%.