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Theoretical and Computational Molecular Science Fujita group

Location: Myoudaiji, South Laboratory Bldg. Room414
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Exciton, Energy and Charge Transfer, Organic Semiconductors

Theoretical Studies on Molecular Aggregates

Organic molecules can assemble into an ordered structure by non-covalent interactions, forming various types of aggregates. Molecular aggregates exhibit characteristic optical and electronic properties that are not observed in isolated molecules; those optoelectronic properties are desirable for producing flexible and low-cost devices. For example, a large number of molecules can behave cooperatively due to their intermolecular interactions, and they can form a collective electronic excited state by light absorption. Another characteristic photophysical process of molecular aggregates is fluorescence resonant energy transfer, where an electronic excited state is transferred from one molecule to another. In addition, when the intermolecular distance is so close that the intermolecular orbital overlaps become significant, charge separation can take place. Our research targets are optoelectronic properties and photophysical processes that emerge as a result of the molecular aggregation.

We study optoelectronic properties and quantum dynamics of molecular aggregates. More specifically, we focus on energy and charge transfer dynamics, energy conversions, and structure-property relationship. We currently investigate electronic structures and exciton dynamics in organic optoelectronic materials, such as an organic/organic interface. We also develop an ab initio theory suitable to treat electronically excited states of large systems with reasonable accuracy, on the basis of a fragment-based theory and a many-body perturbation theory.


Fig1:(a) Schematic picture of excitation energy transfer in the chlorosome light-harvesting antenna system. (b)Time-dependent polarization anisotropy.

2018_fujita2.pngFig2:(a) Schematic picture of the exciton in a thin film of p-type organic semiconductor molecules (b)Delocalization length of electron (red) and hole (blue)
wavefunctions and electron-hole separation (green).


Selected Publications

  1. T. Fujita, J. Huh, S. K. Saikin, J. C. Brookes, A. Aspuru-Guzik, "Theoretical characterization of excitation energy transfer in chlorosome light-harvesting antennae from green sulfur bacteria," Photosynth. Res. 120, 273-289 (2014).
  2. T. Fujita, S. Atahan-Evrenk, N. P. D. Sawaya, A. Aspuru-Guzik, "Coherent Dynamics of Mixed Frenkel and Charge Transfer Excitons in Dinaphtho[2,3-b:2'3'-f] thieno[3,2-b]-thiophene Thin Films: The Importance of Hole Delocalization," J. Phys. Chem. Lett. 7, 1374-1380 (2016).