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July 22, 2026 02:20 PM

Design Principles of Charge Transfer and Charge Separation in Organic Solar Cells and Functionalized Two-Dimensional Materials

Prof. Hiroshi Imahori from Department of Molecular Engineering, Kyoto University, Kyoto, Japan

@ CCMS/PHYSICS BUILDING R212

Abstract

Light energy conversion is a fundamental process that occurs widely in nature, science, and technology. In this regard, our research has focused on organic solar cells (OSCs) to improve solar energy conversion efficiency. We have designed versatile dyes and redox shuttles for dye-sensitized solar cells (DSSCs) and donor/acceptor (D/A) molecules for bulk heterojunction (BHJ) OSCs, aiming to deepen our understanding of their underlying mechanisms and enhance photovoltaic performance. In particular, we have elucidated the intricate relationships among molecular structure, film morphology, photodynamics, and photovoltaic properties in OSCs. Our investigations have addressed: 1) inclined geometries of dyes on TiO2, 2) methylene-bridge-fused structures for DSSCs, 3) effects of copper redox shuttles for DSSCs, 4) isomer effects of fullerene acceptors, 5) long-lived excited states in non-fullerene acceptors (NFA) films, and 6) charge transfer and charge separation in two-dimensional layered materials covalently modified with photoactive molecules. Particular emphasis will be placed on charge transfer and charge separation processes in covalently functionalized transition metal dichalcogenides (TMDs), which provide exciting opportunities for next-generation optoelectronic applications and future collaborations between Taiwan and Japan. This presentation will provide an overview of these initiatives, highlighting how well-tailored model systems can deepen our understanding of charge transfer, charge separation, and light-energy conversion processes in organic and hybrid optoelectronic materials.

 

References

  1. “An Emissive Charge-Transfer Excited-State at Well-Defined Hetero-Nanostructure Interface of Organic Conjugated Molecule and Two-Dimensional Inorganic Nanosheet.” T. Umeyama,* D. Mizutani, Y. Ikeda, W. R. Osterloh, F. Yamamoto, K. Kato, A. Yamakata,* M. Higashi, T. Urakami, H. Sato, H. Imahori.* Chem. Sci., 2023, 14, 11914-11923.
  2. “Ultrafast Charge Transfer and Long-lived Charge Separation in Covalently Linked MoS2-Pyrene-Phenothiazine Heterojunction Monolayers.” M. Kubota, M. Akiyama, W. R. Osterloh, M. Higashi, M. Fuki, A. Yamakata,* Y. Kobori,* H. Imahori.* J. Am. Chem. Soc., 2026, 148, 5744-5753.
  3. “Boosting Charge Separation in Organic Photovoltaics: Unveiling Dipole Variations in Excited Non-Fullerene Acceptor Layers.” A. Yamakata,* K. Kato, T. Urakami, S. Tsujimura, K. Murayama, M. Higashi,* H. Sato, Y. Kobori, T. Umeyama, H. Imahori.* Chem. Sci., 2024, 15, 12686-12694.
  4. “Energy Migration, Charge Transfer, and Charge Dissociation in Self-Assembling Nonfullerene Acceptor Aggregates with Zincporphyrin-Nonfullerene Acceptor Dyads.” Y. Tamai,* M. Akiyama, L. Vallan, D. Sasada, K. Suzuki, H. Kaji,* T. Urakami, H. Sato, M. Higashi,* S. Izawa, M. Kubota, T. Umeyama, H. Imahori.* Chem. Sci., 2025, 16, 15378-15386.

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