Charge dynamics in planar heterojunctions

2018 Fiscal Year Final Research Report

• Project/Area Number: 17K14527
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Energy-related chemistry
• Research Institution: Kyoto University
• Principal Investigator: Tamai Yasunari 京都大学, 工学研究科, 助教 (30794268)
• Project Period (FY): 2017-04-01 – 2019-03-31
• Keywords: 有機薄膜太陽電池 / 過渡吸収分光法 / 電荷分離 / 電荷再結合

Outline of Final Research Achievements

Charge separation and recombination dynamics at donor/acceptor interface is studied by transient absorption spectroscopy. Charge transfer states (CTS) generated at the interface undergoes either long range spatial charge separation or geminate recombination to the ground state. Charge separation undergoes before thermalization through band-like delocalized valence/conduction bands within sub-ps. Geminate recombination undergoes on ps to ns time scale depending on crystallinity near the interface. At lower crystallinity interface, geminate recombination undergoes 57 ps, while it takes 1.7 ns at higher crystallinity interface. This large difference would be attributable to delocalization of charge wave function near the interface. Crystallinity is also important for re-separation of CTS. Bimolecular charge recombination is more suppressed in higher crystalline film, suggesting that potential energy cascade near the interface would enhance re-separation of the CTS.

Free Research Field

高分子光物理

Academic Significance and Societal Importance of the Research Achievements

これまでの研究により材料の結晶性が電子ドナー/アクセプター界面における電荷生成・再結合ダイナミクスに影響を及ぼしていると考えられてきたが、その詳細は十分に理解されているとは言い難かった。本研究により多様な分子形態あるいは集合構造によりヘテロ界面での電荷ダイナミクスがどのように変化するのかを明らかにすることができれば、これまで経験則に頼っていた材料設計に対し、科学的基盤に基づいた明確な設計指針を提示することができる。