Recent advances in cadmium telluride (CdTe) research and development have improved the long-term power output degradation and extended reliability test performance of First Solar’s thin-film CdTe PV modules. This paper reviews the characterization results of the new First Solar cell structure with improved back-contact design that better manages the fundamental power-output degradation mechanism. First Solar's proprietary ‘Black’ series module construction significantly enhances the long-term durability and extended test performance of the modules. The accelerated lab-testing methods, field testing and associated analyses are discussed. These advances in the solar cell performance, coupled with upgraded module materials, further substantiate the long-term power-generating capability of First Solar's CdTe PV modules in harsh operating conditions.