'Double-Cable' conjugated polymers with linear backbone toward high quantum efficiencies in single-component polymer solar cells

A series of "double-cable" conjugated polymers were developed for application in efficient single-component polymer solar cells, in which high quantum efficiencies could be achieved due to the optimized nanophase separation between donor and acceptor parts. The new double-cable polymers contain electron-donating poly(benzodithiophene) (BDT) as linear conjugated backbone for hole transport and pendant electron-deficient perylene bisimide (PBI) units for electron transport, connected via a dodecyl linker. Sulfur and fluorine substituents were introduced to tune the energy levels and crystallinity of the conjugated polymers. The double-cable polymers adopt a "face-on" orientation in which the conjugated BDT backbone and the pendant PBI units have a preferential pi-pi stacking direction perpendicular to the substrate, favorable for interchain charge transport normal to the plane. The linear conjugated backbone acts as a scaffold for the crystallization of the PBI groups, to provide a double-cable nanophase separation of donor and acceptor phases. The optimized nanophase separation enables efficient exciton dissociation as well as charge transport as evidenced from the high-up to 80%-internal quantum efficiency for photon-to-electron conversion. In single-component organic solar cells, the double-cable polymers provide power conversion efficiency up to 4.18%. This is one of the highest performances in single-component organic solar cells. The nanophase-separated design can likely be used to achieve high-performance single-component organic solar cells. Funding Agencies|National Key R&D Program of China [2017YFA0204702]; NSFC of China [51773207, 21574138, 51603209, 91633301]; Strategic Priority Research Program of the Chinese Academy of Sciences [XDB12030200]; Open Research Fund of State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, CAS; Recruitment Program of Global Youth Experts of China; European Research Council (ERC) [339031]; Ministry of Education, Culture and Science [024.001.035]; European Union [747422]; Swedish Research Council [VR621-2013-5561]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [200900971]; China Scholarship Council [CSC201606920028]