| Summary |
Charge separation in organic photovoltaics [1] and singlet fission in molecular crystals [2-4] are analyzed by first principles calculations and quantum dynamics calculations. The charge and exciton dynamics are described by the linear vibronic coupling model parametrized based on dibatization of TDDFT and MRMP2 adiabatic states. Quantum dynamics calculations are carried out using the MCTDH method explicitly considering intra-molecular modes and essential inter-molecular modes.
In organic photovoltaics, charge separation from photo-generated exciton occurs at donor-acceptor interfaces on a time scale of few hundred second despite the small permittivity of organic materials. Our quantum dynamics calculations revealed the role of charge delocalization and hot exciton in the ultrafast charge separation [1].
In the same way, mechanisms of singlet fission in molecular crystals are analyzed using the MCTDH method [2,3]. We clarify the contribution of direct and CT-mediated pathways to the singlet fission rate. The coherent and thermally activated singlet fission in TIPS-pentacene and rubrene are rationalized by the molecular stacking that governs electronic coupling from singlet exciton (S1) to triplet pair (TT) [2]. We also analyzed the singlet fission in hexacene for explaining the intermediate state observed by the TR-2PPE experiments [3]. Further, the separation rate of free triplets from TT is analyzed based on Marcus-Levich-Jortner theory in conjunction with ab initio calculations [4]. Both experiments and theory indicate endothermic TT separations for all materials.
[1] H. Tamura and I. Burghardt, J. Am. Chem. Soc. 135, 16364-16367 (2013).
[2] H. Tamura, M. Huix-Rotllant, I. Burghardt, Y. Olivier, D. Beljonne, Phys. Rev. Lett. 115, 107401-1-5 (2015).
[3] N. R. Monahan, D. Su, H. Tamura, K. W. Williams, B. Xu, Y. Zhong, B. Kumar, C. Nuckolls, A. R. Harutyunyan, G. Chen, H.-L. Dai, D. Beljonne, Y. Rao, X.-Y. Zhu, Nature Chemistry, 9, 341–346 (2017).
[4] C. K. Yong, A. J. Musser, S. L. Bayliss, S. Lukman, H. Tamura, O. Bubnova, R. K. Hallani, A. Meneau, R. Resel, M. Maruyama, S. Hotta, L. M. Herz, D. Beljonne, J. E. Anthony, J. Clark, H. Sirringhaus, Nature Communications, in press.
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