Toward Practical Useful Polymers for Highly Efficient Solar Cells via a Random Copolymer Approach

Using benzo[1,2-b:4,5-b']dithiophene and two matched 5,6-difluorobenzo[2,1,3]thiadiazole-based Monomers, we demonstrate that random-copolymerization of two electron deficient monomers, alternAting with one electron rich monomer, forms a successful approach to synthesize state-of-the-art semiconducting copolymers for organic solar cells. Over a range of compositions, these tandorn: copolymers provide impressive power conversion efficiencies (PCEs) of about 8.0%; higher than those of their binary parent polymers, and with little batch-to-batch variation. A PCE Over 8% could also be achieved when the active layer was deposited from nonhalogenated soWentS at room temperature.