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 C71-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 ∼10 nm, close to the exciton diffusion length in organic materials) and the use of an efficient electron transport layer.
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The authors acknowledge financial support from the Ministry of Science and Technology of China (MoST, 2014CB643502 and 2012CB933401), the National Natural Science Foundation of China (NSFC, 51373078) and the Program for Changjiang Scholars and Innovative Research Team in University (PCSIRT, IRT1257). The morphological characterization of the active layers was supported by the DOE-funded Energy Frontier Research Center on Polymer-Based Materials for Harvesting Solar Energy (DE-SC0001087). Portions of this research were carried out at the Advanced Light Source, Berkeley National Laboratory, which was supported by the DOE, Office of Science and Office of Basic Energy Sciences. The authors also acknowledge Beamline BL14B1 (Shanghai Synchrotron Radiation Facility) for providing beam time.
A patent (application no. CN2014100099426) has been filed for the materials and devices.
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Zhang, Q., Kan, B., Liu, F. et al. Small-molecule solar cells with efficiency over 9%. Nature Photon 9, 35–41 (2015). https://doi.org/10.1038/nphoton.2014.269
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