Intellectual Merit: CdTe based thin film cells have one of the most promising outlooks for wide-spread use due to their low cost and relatively high conversion efficiencies (~16%, to date). At this point, there is a consensus in the field, that further significant efficiency increases need an improvement of the back contact to the light converting CdTe layer. This contact is currently fabricated using Cu, which are affected by degradation over time due to migration of Cu into the CdTe layer of the solar cell, as well as limited conversion efficiency due to non-optimal current transport across the CdTe/Cu boundary. The proposed research will address these issues by investigating a promising class of materials, namely layered compound metals such as VSe2 or TiSe2. These materials distinguish themselves through high chemical inertness (which will reduce or eliminate interfacial reaction and migration) and high work functions, which will optimize the conversion efficiency. Broader Impact: Global warming and dependence on foreign energy sources have caused a renewed interest in alternative energy sources. Direct generation of electric power from photovoltaic cells is one of the most promising options to generate clean energy in a decentralized way. However, commercial viability of solar cells is one of the main challenges on the way to successful competition with fossil energy sources. While CdTe thin film solar cells are currently considered one of the most likely candidates for widespread deployment, increased efficiency is needed to push the CdTe technology into the realm of commercial viability, which is the focus of the proposed research. On the educational side, undergraduates and high school students will be involved in the program working together with the graduate students, giving them an opportunity to experience scientific research hands-on.
