SBIR Phase I: Ultra-Thin Silicon Solar Cells for Lightweight Flexible High-Efficiency Photovoltaic Modules

The broader impact of this Small Business Innovation Research (SBIR) Phase I project will be to support the societal need for higher adoption of clean renewable energy. The new kind of high-efficiency, lightweight and thin photovoltaic modules that will be enabled by this project will be ideal for integration at the factory with roofing materials for Commercial and Industrial (C&I) buildings. This will address half of the U.S. C&I rooftop market (low-slope metal roofs) that is poorly served by existing photovoltaic modules due to weight limits, wind-loading effects and other factors. In addition, it will drop total C&I rooftop photovoltaic system cost by up to 40% through reduction of installation materials and labor, as well as simplification of system design, permitting, etc. This disruptive innovation can turn C&I photovoltaic systems--today the smallest of the 3 major U.S. photovoltaic market segments--into a key driver for US solar growth. This photovoltaic module product is ideally suited for US manufacturing. The SBIR Phase I proposed project will allow the first ever exploration of Silicon heterojunction solar cells with absorber thickness substantially below 40 microns. Higher thickness silicon heterojunction solar cells have already achieved world record efficiency of over 26.5%. For the ultra-thin silicon design targeted by this project, theory predicts an open circuit voltage (Voc) of at least 780mV, well in excess of current records for any silicon solar cell. High Voc will reduce photovoltaic system resistive losses as well as minimizing system performance degradation from high operating temperatures. With respect to solar wafer technology, this would be a new kerfless approach to realizing silicon heterojunction solar cells, leading to a new type of robust flexible thin photovoltaic module, with much higher efficiency, superior reliability, and lower cost compared to current flexible thin film photovoltaic options. In this Phase I project we will target Voc of at least 720mV. We will also investigate optimizing the rear reflector design for silicon heterojunction solar cells, to maximize light absorption in the thin silicon absorber layer. Finally, we will identify a detailed path forward to 24% efficiency for this solar cell design. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.