The molecular structure of polymer photovoltaic materials has a very close relationship with its photovoltaic performance. According to the results reported so far, the optimization of the molecular structure of photovoltaic polymers is mostly performed on a certain polymer. That is, for different molecular structures, one needs to optimize it in different ways. This not only increases the difficulty of the molecular structure optimization work, but also easily leads to missed many potential molecular structural units. Therefore, finding a widely applicable method that can improve the photovoltaic performance of polymers will be a very important task.
With the strong support of the Chinese Academy of Sciences, the Ministry of Science and Technology, the National Natural Science Foundation of China, and the Institute of Chemistry, the State Key Laboratory of Polymer Physics and Chemistry and the Key Laboratory of Organic Solids Institute of Chemical Institute recently obtained the molecular structure design of polymer photovoltaic materials. Series progress.
The researchers introduced a two-dimensional conjugated structure into a benzodithiophene (BDT) unit and designed the thiophene-substituted BDT two-dimensional conjugated structural unit shown in Figure 1, and combined this unit with various conjugated structural units. Copolymerization gave a series of conjugated polymers with two-dimensional conjugated structures. Photovoltaic test results show that this type of two-dimensional conjugated polymer has an effective increase in photovoltaic energy conversion efficiency (PCE) compared with alkoxy-substituted corresponding polymers. Related results were published in Macromolecules 2011, 44, 4035; Macromolecules 2012, 45, 3032; Macromolecules 2012, DOI: 10.1021/ma301254x; Chem. Commun. 2011, 47, 8850; J. Mater. Chem. 2012, DOI: 10.1039/c2jm32931j)). Among them, the efficiency of a polymer solar cell based on a two-dimensional conjugated polymer PBDTTT-CT was increased to 7.6% (Angew. Chem. Int. Ed., 2011, 50, 9697). In cooperation with the University of Hong Kong, they have further increased the photovoltaic efficiency of PBDTTT-CT to 8.79% through the use of new device structures (Adv. Mater., 2012, 24, 3046). PBDTTT-CT is one of the best polymer photovoltaic materials currently available. They also collaborated with researchers at the University of Massachusetts in the United States to clearly characterize the active layer topography of polymer solar cells by scanning X-ray diffraction (Adv. Mater., 2012, 24).
At the same time, the researchers also introduced the strong electron-withdrawing group sulfonyl into the polymer PBDTTT to synthesize PBDTTT-S, the polymer has a lower HOMO level, the PCE based on the PBDTTT-S photovoltaic device reaches 6.22%, and the open circuit voltage reaches 0.76 V (Chem. Commun. 2011, 47: 8904). Recently, they prepared a two-dimensional conjugated polymer, PBDTDTTT-ST, by inserting a thiophene p-bridge and thiophene. The polymer has a good planar structure and strong interchain interactions. Based on PBDTDTTT-ST polymer solar energy. The PCE of the battery reaches a maximum of 7.81% (Adv. Mater., 2012, 24, 3383).
It should be pointed out that the improvement of the photovoltaic performance of polymers using the two-dimensional conjugate concept was first proposed by researchers at the Institute of Chemistry in 2004 (patent: (1) “A branched conjugated polythiophene derivative material and its preparation Method, Chinese Invention Patent, Date of Filing: November 1, 2004. Announcement of Authorization: October 31, 2007, Patent No.: ZL 2004 1 0088723.8; (2) "A two-dimensional conjugated polymer and its Preparation Method and Application", Chinese Invention Patent, Filing Date: November 20, 2005. Authorization Announcement Date: May 5, 2010, Patent Number: ZL 2005 1 0132380.5; Representative Paper: J. Am. Chem. Soc ., 2006, 128, 4911; Macromolecules, 2006, 39, 594). The current research results are a continuation of their research work on two-dimensional conjugated polymer photovoltaic materials.
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