Absorption tails of donor:C60 blends provide insight into thermally activated charge-transfer processes and polaron relaxation

Vandewal K, Benduhn J, Schellhammer KS, Vangerven T, Rueckert JE, Piersimoni F, Scholz R, Zeika O, Fan Y, Barlow S, Neher D, Marder SR, Manca J, Spoltore D, Cuniberti G, Ortmann F (2017)

Publication Type: Journal article

Publication year: 2017

Journal

Journal of the American Chemical Society American Chemical Society

Book Volume: 139

Pages Range: 1699-1704

Journal Issue: 4

DOI: 10.1021/jacs.6b12857

Abstract

In disordered organic semiconductors, the transfer of a rather localized charge carrier from one site to another triggers a deformation of the molecular structure quantified by the intramolecular relaxation energy. A similar structural relaxation occurs upon population of intermolecular charge-transfer (CT) states formed at organic electron donor (D)-acceptor (A) interfaces. Weak CT absorption bands for D-A complexes occur at photon energies below the optical gaps of both the donors and the C60 acceptor as a result of optical transitions from the neutral ground state to the ionic CT state. In this work, we show that temperature-activated intramolecular vibrations of the ground state play a major role in determining the line shape of such CT absorption bands. This allows us to extract values for the relaxation energy related to the geometry change from neutral to ionic CT complexes. Experimental values for the relaxation energies of 20 D:C60 CT complexes correlate with values calculated within density functional theory. These results provide an experimental method for determining the polaron relaxation energy in solid-state organic D-A blends and show the importance of a reduced relaxation energy, which we introduce to characterize thermally activated CT processes. (Figure Presented).

Involved external institutions

Technische Universität Dresden DE Germany (DE) Hasselt University / Universiteit Hasselt BE Belgium (BE) Universität Potsdam DE Germany (DE) Georgia Institute of Technology US United States (USA) (US)

How to cite

APA:

Vandewal, K., Benduhn, J., Schellhammer, K.S., Vangerven, T., Rueckert, J.E., Piersimoni, F.,... Ortmann, F. (2017). Absorption tails of donor:C60 blends provide insight into thermally activated charge-transfer processes and polaron relaxation. Journal of the American Chemical Society, 139(4), 1699-1704. https://doi.org/10.1021/jacs.6b12857

MLA:

Vandewal, Koen, et al. "Absorption tails of donor:C60 blends provide insight into thermally activated charge-transfer processes and polaron relaxation." Journal of the American Chemical Society 139.4 (2017): 1699-1704.

BibTeX: Download