Recent Progress in Cd(Se,Te) Photovoltaics from NREL

The push to improve efficiency in Cd(Se,Te) photovoltaics centers around improving the extracted photovoltage. In 2016, the National Renewable Energy Laboratory (NREL) demonstrated using CdTe single crystals that a new defect chemistry, namely doping with a group V element in place of Cu, was a path to improve voltage while enhancing stability. Since then, the broader community has been striving to implement this in polycrystalline thin films that have been alloyed with Se. Successfully achieving this requires simultaneously improving doping, bulk minority carrier lifetime, and interface recombination by at least an order of magnitude each over historic CdTe:Cu devices. Progress has required a more detailed scientific understanding of the material system and its challenges. This talk will focus on contributions from NREL over the past few years towards this goal. These include modeling to help understand losses in real devices, a technique to expose buried interfaces and how they evolve, characterizations that reveal our material limitations, as well as synthesis strategies to address these in the bulk and contacts. Depending on the schedule of other talks, some more contextualization of this research will also be presented.