2018 Fiscal Year Final Research Report
Statistical mechanical approach to study charge separation and recombination in organic photovoltaic materials
| Project/Area Number |
15K05406
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Multi-year Fund |
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| Section | 一般 |
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| Research Field |
Physical chemistry
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| Research Institution | National Institute of Advanced Industrial Science and Technology |
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Principal Investigator |
Seki Kazuhiko 国立研究開発法人産業技術総合研究所, 材料・化学領域, 上級主任研究員 (60344115)
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| Research Collaborator |
Wojcik Mariusz
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| Project Period (FY) |
2015-04-01 – 2019-03-31
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| Keywords | エキシトン / 拡散 / 再結合 / 有機薄膜太陽電池 |
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| Outline of Final Research Achievements |
In organic photovoltaic cell materials, the dissociation of photogenerated charge pairs occurs against a strong Coulomb binding energy. The strength of Coulomb binding energy can be characterized by the Onsager radius, which is defined as the distance at which the Coulomb binding energy is equal to the thermal energy. We studied sensitivity of the ultimate dissociation yield to the assumed form of angular dependence of the charge separation rate using the Marcus equation. Using the exact numerical results, we have shown that this sensitivity is very limited because of length scale separation between the Onsager radius and the molecular scale. By assuming length scale separation, we have derived an analytical expression that describes the electric field dependence of dissociation yield. We have also shown that the field effect on the electron-hole separation probability in donor-acceptor heterojunction systems is weaker than in homogeneous systems by using lattice simulation results.
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| Free Research Field |
物理化学
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| Academic Significance and Societal Importance of the Research Achievements |
有機太陽電池の光吸収、電荷分離、電荷輸送の一連の過程を理論的に研究することにより、光電変換効率を上げるための指針を得ることができる。学術的には、電荷対の解離確率が電場に強く依存する事は、最初にOnsagerによって示された。Onsagerが求めたのは点電荷の解離確率であるが、分子性を考慮した厳密解が既に知られている。その結果はOnsagerの結果よりも複雑過ぎるという欠点があった。本研究では、厳密解を用いて数値解を得る際の注意点を明らかにし、誘電率が低い極限で成立する電場依存性を表す簡便な近似解を求めた。誘電率に対する制約があるが、実験の解析やシミュレーションに組み込むことが可能である。
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