Electrochemical Polymerization-Fabricated Several Triphenylamine–Carbazolyl-Based Polymers with Improved Short-Circuit Current and High Adsorption Stability in Dye-Sensitized Solar Cells

Polymer dyes have many potential advantages, such as high molecular weight, better light capture ability, thermal stability, film-forming ability, light resistance, and electrochemical corrosion resistance. They are expected to provide opportunities for the development of high-stability dye-sensitized solar cells (DSCs). However, polymer DSCs (PDSCs) have poor short-circuit current and filling factor (FF) due to polymer aggregation and chain-winding effect. Therefore, the energy conversion efficiency is low. In this work, we are trying to find a way to solve this problem. Herein, three polymers, polyPAC-01, polyPAC-02, and polyPAC-03 with different π-bridge chains were prepared on a titanium dioxide electrode using an “adsorption first, then electropolymerization (EP)” process. Meanwhile, as a comparison, three oligomers, PAC-01, PAC-02, and PAC-03 with the same skeleton were synthesized by the Suzuki coupling reaction and fabricated on a titanium dioxide electrode with a “first polymerization, then adsorption” process. Then, the photoanode adsorbed by those polymers or oligomers were applied to DSCs. The results show that polymers prepared by the EP method obtained a higher short-circuit (Jsc) increase, exceeding 30% and a FF increase of about 10%, and finally, the photo-to-electric conversion efficiency (PCE) increased exceeding 40%, compared to the oligomers. In addition, desorption experiments in a harsh environment show that the EP method-synthesized polymers (polyPAC-03 as a representative) have better solvent resistance and adsorption stability than the corresponding oligomers (PAC-03). The results show that the process of “adsorption first, then EP” may be an effective way to solve the bottlenecks of low energy conversion efficiency on PDSCs and provide a new way to develop stable and efficient DSCs.