Ternary System with Intermolecular Hydrogen Bond: Efficient Strategy to High-Performance Nonfullerene Organic Solar Cells

To boost organic solar cell (OSC) performance, numerous approaches have been developed, such as synthesizing new materials, using post-annealing (thermal or solvent annealing) or fabricating ternary devices. The ternary strategy is usually used as an uncomplicated and effective way, but how to choose the third component and the effect of interactions between materials on OSC performance still need to be clarified. Herein, we proposed a new finding that the carbonyl group of 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) end groups can react with the dye molecule SR197 to form the N-H···O noncovalent interaction. The existence of intermolecular hydrogen bonds was confirmed using Fourier transform infrared spectra and two-dimensional proton nuclear magnetic resonance. The power conversion efficiency (PCE) was improved to 10.29% via doping SR197 into blends of PTB7-Th:ITIC, which exhibited a huge enhancement of approximately 30% compared with the binary OSCs (PCE = 7.92%). The ternary OSCs of PBDB-T:SR197:ITIC could also achieve high PCE (11.03%) without post-thermal or solvent annealing. Transmission electron microscopy and grazing-incidence wide-angle X-ray scattering showed the optimized morphology and enhanced crystallinity of ternary systems, which is facilitated to exciton dissociation and charge transmission. These conclusions mean that the H-bonding strategy is an effective way for selecting the third component and could achieve high-performance OSCs.