Abstract
Solar cells based on copper ternary chalcogenide compounds and alloys have emerged over the last 20 years as a promising solution to the problem of high-cost solar cells. Solar power conversion efficiencies exceed 21% in laboratory devices using thin films of these materials, and their characteristic thinness results in negligible direct materials costs per unit area compared with wafers. Photovoltaic devices made from these materials have also been shown to be intrinsically stable, circumventing the historical disadvantage of degradation typical of earlier thin film solar cell technologies. However, these copper chalcogenide devices and materials are relatively complex. This article provides an overview of the current state of our scientific understanding and technological development of them.