Efficient Ternary Organic Solar Cells With Small Aggregation Phases and Low Bimolecular Recombination Using ICBA: ITIC Double Electron Acceptors

The influence of binary acceptors of indene-C60 bisadduct (ICBA) and 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) on the photovoltaic performances of ternary organic solar cells (OSCs) were systemically investigated. Under 20 wt% ICBA, the simultaneously improvements in the short circuit current and fill factor are achieved without energy loss in the open-circuit voltage (VOC), which result in a 26.2% enhancement of power conversion efficiency (PCE) compared with the conventional binary device. This phenomenon is attributed to more light harvesting in the short wavelength spectrum, better exciton dissociation because of the small aggregation phases of film morphology and higher holeelectron mobility, which are significantly beneficial for efficient charge generation and collection. Furthermore, the impedance spectra analysis suggests that proper low concentration of ICBA in the ITIC-based bulk blend is conductive to decrease the series resistance, form an ideal interfacial capacitor and suppress the bimolecular recombination. The ICBA-ITIC-based ternary structure is helpful to design highly efficient OSCs with overall performance improvement, especially to maintain high VOC.