Small-molecule solar cells with efficiency over 9%

At present, state-of-the-art single-junction organic photovoltaic devices have power conversion efficiencies of >9% and >8% for polymer- and small-molecule-based devices, respectively. Here, we report a solution-processed organic photovoltaic device based on DRCN7T, which employs an oligothiophene-like small molecule with seven conjugation units as the backbone and 2-(1,1-dicyanomethylene)rhodanine as the terminal unit. With [6,6]-phenyl C-71-butyric acid methyl ester (PC71BM) as the acceptor, an optimized power conversion efficiency of 9.30% (certified at 8.995%) is achieved. The DRCN7T-based devices have a nearly 100% internal quantum efficiency, which we believe is due to an optimized nanoscale interpenetrating donor/acceptor network (with highly crystalline donor fibrils with diameters of similar to 10 nm, close to the exciton diffusion length in organic materials) and the use of an efficient electron transport layer.