Highly Efficient Flexible Roll-to-Roll Organic Photovoltaics Based on Non-Fullerene Acceptors.

The ability of organic photovoltaics (OPVs) to be deposited on flexible substrates by roll-to-roll (R2R) processes is highly attractive for rapid mass production. Many research teams have demonstrated the great potential of flexible OPVs. However, the fabrication of R2R-coated OPVs is quite limited. There is still a performance gap between the R2R flexible OPVs and the rigid OPVs. In this study, we demonstrate the promising photovoltaic characteristics of flexible OPVs fabricated from blends of low bandgap polymer poly[(2,6-(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)-benzo[1,2-b:4,5-b']dithiophene))-alt-(5,5-(1',3'-di-2-thienyl-5',7'-bis(2-ethylhexyl)benzo[1',2'-c:4',5'-c']dithiophene-4,8-dione)] (PBDB-T) and non-fullerene 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone))-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2',3'-d']-s-indaceno[1,2-b:5,6-b']dithiophene (ITIC). We successfully R2R slot-die coated the flexible OPVs with high power conversion efficiency (PCE) of over 8.9% under irradiation of simulated sunlight. Our results indicate that the processing parameters significantly affect the PCE of R2R flexible OPVs. By adjusting the amount of solvent additive and processing temperature, as well as optimizing thermal annealing conditions, the high PCE of R2R slot-die coated OPVs can be obtained. These results provide significant insights into the fundamentals of highly efficient OPVs for the R2R slot-die coating process.