Scientists are researching organic photovoltaic cells as a cheaper alternative energy source to traditional silicon solar cells. Organic cells use carbon-based conjugated polymers and molecules that can be easily processed and are flexible. Various architectures for organic solar cells have been investigated, including single layer cells, bilayer cells with donor and acceptor materials, and bulk heterojunction cells with the donor and acceptor mixed together. Researchers aim to increase the power conversion efficiency of polymer-fullerene bulk heterojunction solar cells to 8-10% through improved materials and device design.