Effect of molecular weight of oligomer on ionic diffusion in oligomer electrolytes and its implication for dye-sensitized solar cells |
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Authors: | Jong Hyuk Park Kyu Jin Choi Junkyung Kim Yong Soo Kang Sang-Soo Lee |
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Affiliation: | 1. Polymer Hybrids Research Center, Korea Institute of Science & Technology, Seoul 136-791, Republic of Korea;2. Department of Chemical Engineering, Hanyang University, Seoul 133-791, Republic of Korea |
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Abstract: | This study measures the diffusion coefficients of I− and I3− in oligomer electrolytes as a function of the molecular weight of oligomers and investigates their effect on the performance of dye-sensitized solar cells (DSSCs). The high-diffusion coefficients of ions in an oligomer electrolyte with a lower molecular weight can help to promote the redox mechanism in DSSCs and thereby increase the short-circuit current density. They can also cause a decrease in the open-circuit voltage since a high-diffusion coefficient of I3− is capable of reducing the lifetime of electrons in TiO2 electrodes. To offset these effects, N-methyl-benzimidazole is added to the oligomer electrolytes, thereby improving the open-circuit voltage and fill factor and, consequently, the overall energy-conversion efficiency, which increases to over 5%. A further test involving storage at a high temperature of 75 °C demonstrates that DSSCs employing the oligomer electrolytes show excellent thermal stability over 200 h. |
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Keywords: | Dye-sensitized solar cell Ionic diffusion Poly(ethylene glycol) Molecular weight Non-volatile electrolyte |
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