Dresden 2011 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 31: Organic Semiconductors IV: Excitations and Charges (jointly with HL, DS)
CPP 31.1: Topical Talk
Mittwoch, 16. März 2011, 14:00–14:30, ZEU 222
Control of Charge Carrier Dynamics in Disordered Conjugated Polymers — •Dirk Hertel — Physical Chemistry, University of Cologne, Luxemburgerstr. 116, 50939 Cologne, Germany,
We developed a new method to probe charge carrier mobility on ultrafast time scale [1]. It is based on electric field induced second harmonic generation. The method is applied to prototypical amorphous conjugated polymers of the polyphenylene- and polyfluorene-type. Typically the carrier mobility in these organic polymers decreases with time in a power law fashion from about 1 cm2Vs−1 at 1 ps to its stationary value of about 10−6 cm2Vs−1 in hundreds of ns.
The dynamics of the mobility is discussed. It will be shown, that in nanoscale devices the macroscopic mobility is not adequate to describe charge transport. We study the influence of disorder, morphology and temperature on ultrafast transport. At early times the transport is dominated by tunneling [2] and disorder plays already an essential role. Comparison of transient photocurrents with Monte-Carlo simulation reveals that on-chain transport has to be invoked to rationalize our results [3]. The hopping rates for intrachain transport are much larger compared with interchain transport. The results give access to essential transport properties for the development of advanced theoretical models and may help to design improved solar cells.
[1] A. Devižis, et al. Phys. Rev. Lett. 103, (2009) 027404.
[2] A. Devižis, et al. Phys. Rev. B 82, (2010) 155204.
[3] A. Devizis, et al. Chem. Phys. Lett. 498, (2010) 302.