Electrical characterization and aging of CdTe thin film solar cells with Bi2Te3 back contact

Despite CdTe solar cells have been already industrialized in large scale and modules are already available in the market, still the research for a stable, low cost, high performing back contact is very hot topic. As a matter of fact, it has been shown that the presence of copper in the CdTe device increases efficiency, not only by improving the back contact but also by doping the absorber and enhancing all the electrical properties. However copper is well known to be a degrading element in the device, diffusing down to the front contact. In this paper we present an electrical study and aging tests of a CdTe devices where copper is encapsulated within a Bi2Te3 buffer layer. The solar cells show a remarkable stability and a good efficiency.