Highly efficient inverted ternary organic solar cells with polymer fullerene-free acceptor as a third component material

Abstract

Ternary organic solar cells (OSCs) are fabricate using a single wide-bandgap poly[(2,6-(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)-benzo[1,2-b:4,5-b0]dithiophene))-alt-(5,5-(10,30-di-2-thienyl-50,70-bis(2-ethylhexyl)benzo[10,20-c:40,50-c0]dithiophene-4,8-dione))] (PBDB-T) as the donor material 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) as the acceptor and poly[[N,N′-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-(3,3′-difluoro-2,2′-bithiophene)-5,5′-diyl] (FN2200) as third component materials. Due to the strong absorption ability at the short-wavelength region. The best power conversion efficiency (PCE) of 10.9% is achieve for the OSCs via incorporating 10 wt% FN2200 in blend-acceptor materials, with an enhance the short-circuit current (JSC) of 17.6 mA cm−2, fill factor (FF) of 68.0% and stable open-circuit voltage (VOC) of 0.91 V relative to binary OSCs. The short-wavelength absorption windows of FN2200 is favourable the harvesting of as many as possible photons and the enhance exciton dissociation ratio at the ITIC/FN2200 interface due to the deeper LUMO energy level of FN2200 relative to ITIC molecule. Meanwhile, the incorporation small amount of FN2200 is weaken monomolecular recombination and bimolecular recombination under open-circuit and short-circuit conditions respectively and enhance the charge carrier mobility. The use of PBDB-T as donor and the blend of ITIC and FN2200 as an electron acceptor provides a useful strategy for exploring high-performance ternary OSCs.