Theoretical clarification of photo-induced charge separation mechanisms of organic photovoltaics

• Project/Area Number: 24550006
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Physical chemistry
• Research Institution: Tohoku University
• Principal Investigator: TAMURA Hiroyuki 東北大学, 原子分子材料科学高等研究機構, 助教 (60390655)
• Project Period (FY): 2012-04-01 – 2015-03-31
• Project Status: Completed (Fiscal Year 2014)
• Budget Amount: ¥5,720,000 (Direct Cost: ¥4,400,000、Indirect Cost: ¥1,320,000); Fiscal Year 2014: ¥650,000 (Direct Cost: ¥500,000、Indirect Cost: ¥150,000); Fiscal Year 2013: ¥650,000 (Direct Cost: ¥500,000、Indirect Cost: ¥150,000); Fiscal Year 2012: ¥4,420,000 (Direct Cost: ¥3,400,000、Indirect Cost: ¥1,020,000)
• Keywords: 有機太陽電池 / 励起子 / 電子移動 / 量子ダイナミックス / 第一原理計算 / 電荷分離 / 有機薄膜太陽電池 / 量子化学 / 量子動力学

Outline of Final Research Achievements

In organic photovoltaics, the mechanism by which free electrons and holes are generated overcoming the Coulomb attraction is a currently much debated topic. To elucidate this mechanism at a molecular level, we carried out a combined electronic structure and quantum dynamical analysis that captures the elementary events from the exciton dissociation to the free carrier generation at polymer/fullerene donor-acceptor hetero-junctions. Our calculations show that experimentally observed efficient charge separations can be explained by a combination of two effects: First, the delocalization of charges which substantially reduces the Coulomb barrier, and second, the vibronically hot nature of the charge transfer state which promotes charge dissociation beyond the barrier.

Research Products

• [Journal Article] Large-scale conductivity-tensor calculations for Hall effects in time-dependent wave-packet diffusion method (2014)
  • Author(s): H. Ishii, H. Tamura, M. Tsukada, N. Kobayashi1, and K. Hirose
  • Journal Title: Phys. Rev. B Volume: 90
  • DOI: 10.1103/physrevb.90.155458
  • Peer Reviewed / Open Access
• [Journal Article] Non-Markovian reduced dynamics of ultrafast charge transfer at an oligothiophene–fullerene heterojunction (2014)
  • Author(s): K. H. Hughes, B. Cahier, R. Martinazzo, H. Tamura, I. Burghardt
  • Journal Title: Chem. Phys. Volume: 442 Pages: 111-118
  • DOI: 10.1016/j.chemphys.2014.06.015
  • Peer Reviewed / Open Access
• [Journal Article] Exciton diffusion length and charge mobility in donor and acceptor materials in organic photovoltaics: tetrabenzoporphyrin and silylmethyl[60]fullerene (2014)
  • Author(s): H. Tamura and Y. Matsuo
  • Journal Title: Chem. Phys. Lett. Volume: 598 Pages: 81-85
  • DOI: 10.1016/j.cplett.2014.03.013
  • Peer Reviewed / Open Access / Acknowledgement Compliant
• [Journal Article] Ultrafast charge separation in organic photovoltaics enhanced by charge delocalization and vibronically hot exciton dissociation (2013)
  • Author(s): H. Tamura, I. Burghardt.
  • Journal Title: J. Am. Chem. Soc. Volume: 135 Pages: 16364-16367
  • DOI: 10.1021/ja4093874
  • Peer Reviewed
• [Journal Article] Potential barrier and excess energy for electron－hole separation from the charge-transfer exciton at donor-acceptor heterojunctions of organic solar cells (2013)
  • Author(s): H. Tamura, I. Burghardt.
  • Journal Title: J. Phys. Chem. C Volume: 117 Pages: 15020-15025
  • DOI: 10.1021/jp406224a
  • Peer Reviewed
• [Journal Article] Theoretical Analysis on the Optoelectronic Properties of Single Crystals of Thiophene-furan-phenylene Co-Oligomers : Efficient Photoluminescence due to Molecular Bending (2013)
  • Author(s): H. Tamura, I. Hamada, H. Shang, K. Oniwa, Md. Akhtaruzzaman, T. Jin, N. Asao, Y. Yamamoto, T. Kanagasekaran, H. Shimotani, S. Ikeda and K. Tanaigaki
  • Journal Title: Journal of Physical Chemistry C Volume: 117巻 Pages: 8072-8078
  • DOI: 10.1021/jp400646n
  • Peer Reviewed
• [Journal Article] Influence of Strong Electron-Phonon Coupling and Dynamic Lattice Disorder on the Hall Effect in Organic Crystals (2013)
  • Author(s): H. Tamura, M. Tsukada, H. Ishii, N. Kobayashi, and K. Hirose
  • Journal Title: Phys. Rev. B Volume: 87
  • Peer Reviewed
• [Journal Article] Quantum dynamics of ultrafast charge transfer at an oligothiophene-fullerene heterojunction (2012)
  • Author(s): H. Tamura, R. Martinazzo, M. Ruckenbauer, and I. Burghardt
  • Journal Title: J. Chem. Phys. Volume: 137
  • Peer Reviewed
• [Journal Article] Roles of intramolecular and intermolecular electron-phonon coupling on the formation and transport of large polarons in organic semiconductors (2012)
  • Author(s): H. Tamura, M. Tsukada, H. Ishii, N. Kobayashi, and K. Hirose
  • Journal Title: Phys. Rev. B 86 Volume: 86
  • Peer Reviewed
• [Journal Article] Role of Intermolecular Charge Delocalization on Electron Transport in Fullerene Aggregates (2012)
  • Author(s): H. Tamura and M. Tsukada
  • Journal Title: Phys. Rev. B Volume: 85
  • Peer Reviewed
• [Presentation] 有機薄膜太陽電池の光電変換機構の理論研究 (2014)
  • Author(s): 田村宏之
  • Organizer: 日本化学会東北大会
  • Place of Presentation: 山形大学
  • Year and Date: 2014-09-21
  • Invited
• [Presentation] How does electron-hole pair separate into free carriers at donor-acceptor interfaces overcoming the Coulomb attraction? : Theoretical analysis for clarifying the mechanism (2014)
  • Author(s): Hiroyuki Tamura
  • Organizer: EMN summer meeting
  • Place of Presentation: Cancun, Mexico
  • Year and Date: 2014-06-09 – 2014-06-12
  • Invited
• [Presentation] どのように電子-正孔対がドナー-アクセプター界面でクーロン障壁を越えてフリーキャリアへ分離するのか：機構解明のための理論研究
  • Author(s): 田村宏之
  • Organizer: 応用物理学会
  • Place of Presentation: 青山学院大学
• [Remarks] プレスリリース「有機薄膜太陽電池の電荷損失を防ぐ要因を理論的に解明」（2013 11/11）
  • URL: http://www.wpi-aimr.tohoku.ac.jp/jp/news/press/2013/20131111_000425.html
• [Remarks] 東北大学WPI-AIMRリサーチハイライト「太陽電池: 電荷分離が高効率化の鍵」
  • URL: http://research.wpi-aimr.tohoku.ac.jp/jpn/research/805