New low band gap alternating polyfluorene copolymer-based photovoltaic cells |
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| Authors: | Wendimagegn Mammo, Shimelis Admassie, Abay Gadisa, Fengling Zhang, Olle Ingan s,Mats R. Andersson |
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| Affiliation: | aDepartment of Chemistry, Addis Ababa University, P.O. Box 1176, Addis Ababa, Ethiopia;bBiomolecular and Organic Electronics, IFM, Center of Organic Electronics, Linköpings Universitet, SE-58183 Linköping, Sweden;cPolymer Technology, Department of Chemical and Biological Engineering, Chalmers University of Technology, SE-41296 Göteborg, Sweden |
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| Abstract: | New low band gap alternating polyfluorene copolymers were synthesized for use in plastic solar cells and their optical, electrochemical, and photovoltaic characteristics were determined. These polymers incorporated fluorene units alternating with groups including electron-withdrawing (A) and electron-donating (D) groups in donor–acceptor–donor (DAD) sequence to achieve the lowering of band gaps. The HOMO–LUMO values were estimated from electrochemical studies. By varying the donor and acceptor strength and position of the solubilizing substituents, similar HOMO values were obtained. These values were also found to correlate well with the open circuit voltage (VOC) values determined from photovoltaic data of the polymers blended with the acceptor PCBM. Despite similar HOMO values, the absorption spectra of the polymers differ significantly. This prompted the preparation of photovoltaic devices consisting of blends of two polymers with complementary absorptions in combination with PCBM to harvest more photons in the polymer solar cells. |
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| Keywords: | Polymer solar cell Low band gap polymer |
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