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《Joule》:Scientists improve the performance of solar cell

2019-06-06 来源:转载自第三方
A Chinese and foreign joint research group has recently made new breakthroughs in the single-component organic solar cell with fewer types of conjugated materials, difficult regulation of condensed structure, and low energy conversion efficiency. They synthesized a new dual-cable conjugated polymer that was used as a light absorbing layer in a one-component organic solar cell, achieving a 6.3% energy conversion efficiency, which is the highest efficiency of single-component organic solar cells.
"The polymer contains the donor backbone and the acceptor side chain. During the film formation process, the donor and the acceptor are mutually restricted, making it difficult to form ordered nanostructures. We have found that temperature gives the opportunity for secondary crystallization of such polymers. As the temperature increases, the stacking of the donor backbone and the acceptor side chain in the polymer film is gradually ordered, which greatly improves the charge transport efficiency and reduces the charge recombination probability.” The research team leader, the Chinese Academy of Sciences Li Weiwei, a professor at Beijing University of Chemical Technology, told the Journal of Chinese Academy of Sciences.
It is reported that the single-component organic solar cell has only one component in the active layer compared with the conventional multi-component bulk heterojunction cell, thereby greatly improving device stability and simplifying the device fabrication process. Moreover, single-component organic solar cells based on double-cable conjugated polymers have been shown to be better than the corresponding bulk heterojunction cells because the donors and acceptors are "bound" by chemical bonds and their activity is limited. At the same time, in the double-cable conjugated polymer, the donor and acceptor interfaces are uniformly distributed on the molecular scale, which facilitates the diffusion of excitons to the interface within a limited lifetime. Therefore, single-component solar cells based on double-cable conjugated polymers have potential for large-scale industrial applications.
Although this type of battery has been studied for decades, its efficiency is still far lower than that of bulk heterojunction batteries. The main reason is that the synthesis of single-component conjugated materials is complicated, and the phase separation and regulation of intramolecular donor/acceptor is difficult. Based on this, Li Weiwei's research team regained its historical problem - single-component organic solar cell research.
Previously, in response to the complex problem of double-cable conjugated polymer synthesis, the group proposed a design idea of “first side chain functionalization, post-polymerization”, and successfully prepared a series of well-defined double-cable conjugated polymers. The mechanism of the molecular structure of the conjugated main chain, the acceptor side chain and the linking unit on the condensed structure of the polymer was investigated, and the efficiency of the single-component organic solar cell was increased from 0.51% to 4.34%.
This time, Li Weiwei's research team, together with researchers from the University of Nuremberg, the Hong Kong University of Science and Technology, introduced benzodithiophenedione into the conjugated backbone to synthesize a fourth series of double-cable conjugated polymers, and found the polymer in the film. The phase separation morphology is sensitive to temperature. As the annealing temperature increases, the polymer donor backbone and acceptor side chains become more ordered, and the related solar cells achieve a photoelectric conversion efficiency of 6.3%.
The researchers also systematically studied the many mechanisms of the battery at work, and found that it can maintain an initial efficiency of 93% after 300 hours of continuous sunlight intensity.
The researchers said that this series of studies proves that with the development of new materials and the research of photoelectric conversion mechanism, the one-component organic solar cell "old pot new wine" has great research value and application potential.
It is reported that the first author of the paper is Feng Guitao, a Ph.D. student of the research group. The author of the communication is Li Weiwei and Li Cheng, an associate researcher at the Institute of Chemistry of the Chinese Academy of Sciences.
Edited by Suzhou Yacoo Science Co., Ltd.