Thiophene Rings Improve the Device Performance of Conjugated Polymers in Polymer Solar Cells with Thick Active Layers |
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| Authors: | Chunhui Duan Ke Gao Fallon J M Colberts Feng Liu Stefan C J Meskers Martijn M Wienk René A J Janssen |
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| Affiliation: | 1. Molecular Materials and Nanosystems, Institute for Complex Molecular Systems, Eindhoven University of Technology, MB, Eindhoven, The Netherlands;2. Department of Physics and Astronomy and Collaborative Innovation Center of IFSA (CICIFSA), Shanghai Jiaotong University, Shanghai, P. R. China;3. Dutch Institute for Fundamental Energy Research, AJ, Eindhoven, The Netherlands |
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| Abstract: | Developing novel materials that tolerate thickness variations of the active layer is critical to further enhance the efficiency of polymer solar cells and enable large‐scale manufacturing. Presently, only a few polymers afford high efficiencies at active layer thickness exceeding 200 nm and molecular design guidelines for developing successful materials are lacking. It is thus highly desirable to identify structural factors that determine the performance of semiconducting conjugated polymers in thick‐film polymer solar cells. Here, it is demonstrated that thiophene rings, introduced in the backbone of alternating donor–acceptor type conjugated polymers, enhance the fill factor and overall efficiency for thick (>200 nm) solar cells. For a series of fluorinated semiconducting polymers derived from electron‐rich benzo1,2‐b:4,5‐b′]dithiophene units and electron‐deficient 5,6‐difluorobenzo2,1,3]thiazole units a steady increase of the fill factor and power conversion efficiency is found when introducing thiophene rings between the donor and acceptor units. The increased performance is a synergistic result of an enhanced hole mobility and a suppressed bimolecular charge recombination, which is attributed to more favorable polymer chain packing and finer phase separation. |
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| Keywords: | active layer fill factor polymer solar cells thick film thiophene ring |
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