Singlet Fission: Chromophores for Exciton Downconversion

Alexandr Zaykov^a, Josef Michl^b, Zdeněk Havlas^a, Eric Buchanan^b, Milena Jovanović^b

^aInstitute of Organic Chemistry and Biochemistry of the CAS, Flemingovo náměstí, 2, Praha, Czech Republic

^bDepartment of Chemistry and Biochemistry, University of Colorado, Boulder 80309, United States

Materials for Sustainable Development Conference (MATSUS)
Proceedings of nanoGe Fall Meeting19 (NFM19)

#Exciup19. Excitonic up-downconversion

Berlin, Germany, 2019 November 3rd - 8th

Oral, Alexandr Zaykov, presentation 172
DOI: https://doi.org/10.29363/nanoge.nfm.2019.172
Publication date: 18th July 2019

Singlet fission is a photophysical phenomenon in which a singlet exciton shares energy with a ground state molecule forming two triplet excitons. This phenomenon was unveiled more than half a century ago but the pursuit of it was resurrected only recently due to the fact that it might lead to an efficient way of exciton downconversion. The harnessing of it may lead to a jump in efficiency of solar cells breaking the Shockley-Queisser limit.[1],[2] Because the phenomenon includes the interaction of at least two molecules, the aim of our work is to provide simple methodology of obtaining optimal mutual disposition of such chromophore molecules. This is done through a scan of the whole 6-D space of rotations and translations of two chromophore molecules. We show this on a model molecule of ethylene but also on molecules of practical interest. In all these cases, qualitative guidelines may be observed that steer away from simple comparison of coupling elements expanding it with the discussion of effects of dimer interaction (Davydov splitting) affecting the viability of the examined structure. The results were obtained using an in-house developed program package called "Simple". This package is built upon a theory that revolves around Fermi’s golden rule with various simplifications that have been added to achieve even sub-millisecond calculation times per dimer structure. Following the calculation of SF coupling elements, semi-classical Marcus approximation is employed to explore the kinetics of SF. The other mode program Simple could be used in is as a quick analysis tool of an already synthesized and characterized crystal structures.

References:

[1] M. C. Hanna, A. J. Nozik, J. Appl. Phys. 2006, 100, 074510/1.

[2] W. Shockley, H. J. Queisser, J. Appl. Phys. 1961, 32, 510.

[3] Z. Havlas, J. Michl, Isr. J. Chem. 2016, 56, 96.

[4] E. A. Buchanan, Z. Havlas, J. Michl, in Adv. Quantum Chem., Vol. Volume 75 (Eds.: R. S. John, J. B. Erkki), Academic Press, 2017, pp. 175-227.

[5] M. B. Smith, J. Michl, Chem. Rev. 2010, 110, 6891.

[6] M. B. Smith, J. Michl, Annu. Rev. Phys. Chem. 2013, 64, 361.

Acknowledgements:

This work has been supported by the Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic (RVO: 61388963), and GAČR grants 15-19143S and GBP208/12/G016.

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