Electronic Properties of π-conjugated Materials II - Universität ...

Oral Presentations – 4 π 2011
�antum-chemical contributions to the understanding of
triplet excitons
A. Köhn
Universität Mainz
Knowledge of the energy levels and properties of triplet excited states is vital for the atomistic
understanding of the processes in organic semiconductor devices [1]. Experimentally, direct
optical measurements of triplet states are difficult to conduct due to the spin-forbidden nature
of singlet-triplet transitions. Hence, reliable quantum-chemical calculations are an important
source of information.
In this contribution, we present results from a recent investigation of the triplet energies of
30 state-of-the-art organic semiconductor materials [2]. For this study we employed the ADC(2)
method which includes effects of electron-correlation at second-order perturbation theory [3-
5]. Structural changes in the excited state are fully taken into account. Particularly for multichromophoric
compounds, this effect is important to correctly describe the localization of the
exciton within the molecule. Furthermore, we discuss transient Tn ← T1 absorption spectra
of these compounds. �ese are of particular interest as Tn ← T1 transitions of accumulated
triplet excitons play the main role in inhibiting a continuous wave operation of organic solid
state laser devices [6]. Finally, we will show some initial results from our a�empts to model
exciton diffusion via kinetic Monte Carlo [7].
References
[1] see, e.g., Köhler, Bässler, Mater. Sci. Eng. R 66, 71 (2009)
[2] Pabst, Sundholm, Köhn, in preparation
[3] Schirmer, Phys. Rev. A 26, 2395 (1982)
[4] Hä�ig, Adv. �antum Chem. 50, 37 (2005)
[5] Hä�ig, J. Chem. Phys. 119, 5021 (2003)
[6] Lehnhardt, Riedl, Weimann, Kowalsky, Phys. Rev. B 81, 165206 (2010)
[7] Lunkenheimer, Köhn, Fuchs, Lennartz, May, Andrienko, in preparation
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