(375c) Bulk Heterojunction Polymer Solar Cells Based On Organic Semiconductor Nanomaterials

Polymer solar cells have received increasing attention as a promising alternative for clean and low-cost solar-to-electrical energy conversion technologies. The bulk heterojunction (BHJ) photoactive layer of polymer solar cells requires rational tuning of the nanostructures towards a bicontinuous morphology to achieve maximal power conversion efficiency. The vast number of polymer semiconductors based on various donor- and acceptor-moieties has also enabled a variety of nanostructures. We have synthesized a series of new D-A copolymer semiconductors based on thiazolothiazole or benzobisthiazole building blocks and found them to be excellent p-type materials in polymer/fullerene bulk heterojunction (BHJ) solar cells with high power conversion efficiency (5-6%). Towards air-stable organic solar cells, we have also developed a series of new oligomers and polymers based on naphthalene diimide (NDI) moieties that function as efficient acceptor materials in BHJ polymer solar cells. BHJ solar cells based using NDI acceptors have showed one of the highest photovoltaic efficiencies achieved to date in non-fullerene polymer solar cells. Efficient all-nanowire BHJ solar cells were fabricated based on donor polymer nanowires and acceptor oligomer nanowires. Our results show that donor-acceptor architecture is a powerful means of tuning the molecular structures and nanostructures of polymer/oligomer semiconductors and their photovoltaic properties toward achievement of highly efficient polymer solar cells.