Metal oxide materials could offer earth-abundant, non-toxic alternatives to existing light-absorber materials in thin-film solar cells. However, efficiency of solar cells based on existing metal oxides is typically low due to poor material properties. In this project, researchers at the Worcester Polytechnic Institute (WPI) and the University of Texas at Arlington (UTA) are working on increasing the efficiency of metal oxides by theoretically predicting and experimentally synthesizing metal oxide materials with new compositions and enhanced properties. In addition, efficiency is enhanced by structuring these materials on the nanoscale level. These efforts are guided by terahertz spectroscopy measurements, which are used to understand relationships between the material composition, nanoscale structure and efficiency. The expected outcome of this SusChEM project is essential new knowledge for the development of sustainable thin-film solar cells composed of metal oxides capable of solar energy conversion with practical efficiencies. The project involves training and participation of graduate and undergraduate researchers. In addition, the WPI researchers are developing and delivering workshops and teaching modules on photovoltaics and nanotechnology for middle school girls and high school teachers from local districts serving large populations of low-income, minority and underrepresented students. The UTA researchers are serving African-American and Hispanic high-school students through interactive computer labs.
objective of this SusChEM research is to significantly improve solar energy conversion efficiencies in multi-metal oxides, which could offer earth-abundant, non-toxic alternatives to existing thin-film materials such as CIGS and CdTe. Metal oxides typically suffer from large band gaps or poor charge mobilities, or both, which has thus far restricted their solar-electricity efficiency. This project tackles these issues via three synergistic approaches: i) theoretically predicting and synthesizing new alloys of multi-metal oxides with improved band gaps and higher charge mobilities for solar energy conversion, ii) coating thin layers of these new oxides onto nanowire-array current-collectors to enhance their efficiency and iii) using terahertz spectroscopy to study the bulk carrier dynamics and interfacial charge transfer in these nanostructured oxides and further improve efficiency. This multi-pronged approach is the first to i) investigate new multi-metal oxide alloys that hold much promise for band engineering via alloying while still achieving relatively high mobility, ii) simultaneously apply 'extremely-thin-absorber' nanostructuring and interfacial engineering strategies to improve the charge collection efficiency of multi-metal oxide absorbers and iii) study the ultrafast carrier dynamics in thin metal oxide absorbers on a nanostructured current-collector, focusing on both bulk carrier dynamics and charge extraction at the absorber/current-collector interface.
