Compared to inorganic solar cells, polymer solar cells have significant advantages such as low cost, simple fabrication process, light weight, and the ability to be fabricated into flexible devices. Furthermore, conjugated polymer materials are diverse and highly designable, and their performance can be effectively improved through material modification. Therefore, this type of solar cell has important development and application prospects and has become an important research direction. With the support of the Ministry of Science and Technology, the National Natural Science Foundation of my country, the Chinese Academy of Sciences, and the Institute of Chemistry, researchers at the State Key Laboratory of Polymer Physics and Chemistry of the Institute of Chemistry, Chinese Academy of Sciences, in collaboration with organic solid-state researchers, have recently made a series of advances in conjugated polymer photovoltaic materials.
In wide-bandgap polymer solar cell donor materials, wide-bandgap materials such as MEH-PPV and P3HT have long been important materials for monolayer or tandem photovoltaic devices. Recently, they designed and synthesized a wide-bandgap DA copolymer based on thiazole, which achieved a power conversion efficiency of 5.2%, the highest reported value in the literature for polymer photoelectric conversion efficiency with a bandwidth of over 2.0 eV. The research results were published in Macromolecules (Macromolecules, 2011.44.4035–4037) and became one of the top ten most downloaded papers in the journal that month. They also synthesized the polymer PBDTTT-S by introducing the electron-withdrawing sulfone group into the PBDTTT copolymer for the first time. This polymer has a wide absorption range and a low HOMO energy level. The open-circuit voltage of the polymer solar cell using this polymer as the donor and PC70BM as the acceptor reached 0.76V, and the power conversion efficiency reached 6.22% (Chem. Commun., 2011.47.8904-8906). At the same time, a new polymer photovoltaic material was constructed using the BDP unit, an isomer of the BDT unit, with an open-circuit voltage as high as 0.8V and an efficiency of 5.2% (Chem. Commun., 2011.47.8850-8852).
Recently, researchers replaced the alkoxy groups on the BDT units of PBDTTT-type polymers with thiophene conjugated branches, synthesizing a novel two-dimensional conjugated polymer, PBDTTT-CT (see Figure 1). Compared with PBDTTT-C with alkoxy substituents, PBDTTT-CT exhibits significantly improved hole mobility, a redshift in its absorption spectrum, and a downward shift in its HOMO level, all of which contribute to improved photovoltaic performance. The polymer using PBDTTT-CT as the donor and PC70BM as the acceptor achieved a solar energy conversion efficiency of 7.6%, one of the highest efficiencies among polymer donor photovoltaic materials to date, attracting attention from academic and industrial communities both domestically and internationally (Angew. Chem. Int. Ed., 2011. 50. 9697–9702).
Based on their series of research findings on efficient conjugated polymer photovoltaic materials based on BDT units, they were also invited to write a review article in Polym.Chem. (Polym.Chem., 2011.2.2453-2461).
