In bulk heterojunction (BHJ) polymer solar cells, benzodithiophene (BDT) based copolymers are among the most frequently used donor materials.1There are several reasons for the extensive use and rapid development of BDT based copolymers in BHJ polymer solar cells. First, it is very easy to attach different substituents to the central benzene core by nucleophilic addition thus fine-tuning the solubility and energy levels of the polymers. Second, the BDT core has structural symmetry and rigid fused aromatic system which could enhance the electron delocalization and also the large planar conjugated structure facilitates p-p stacking which is good for improving mobility. Third, for the BDT based polymer, the steric hindrance is small which is good for maintaining the coplanar structure of the polymer. BDT is also a weak donor and it could maintain a low highest occupied molecular orbital (HOMO) energy level of the resulting polymer.In this work, we designed a thienothiophenyl substituted BDT monomer and synthesized new conjugated polymers by Suzuki polymerization. The molecular weight, thermo-, optical-, electrochemical-properties were studied. Application of the polymer in BHJ solar cells provided 4.3% PCE in the initial test. Further optimization of the device performance is still under way.1. Huo, L.; Hou, J. Polym. Chem., 2011, 2  , 2453.

Thienothiophenyl substituted benzodithiophene copolymer: Synthesis, properties and photovoltaic applications

247th National Meeting (2014)

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