Dresden 2011 – scientific programme

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MO: Fachverband Molekülphysik

MO 20: Transport and Spectroscopy in Molecular Nanostructures II (related to SYMN, jointly with CPP)

MO 20.3: Talk

Thursday, March 17, 2011, 11:00–11:15, TOE 317

Time-resolved electron-transfer properties of a low-band-gap neutral mixed-valence polymer — •Florian Kanal¹, Tatjana Quast¹, Martin Kullmann¹, Stefan Ruetzel¹, Johannes Buback¹, Sabine Keiber¹, Dörte Reitzenstein², Christoph Lambert², and Tobias Brixner¹ — ¹Institut für Physikalische und Theoretische Chemie, Universität Würzburg, Am Hubland, 97074 Würzburg — ²Institut für Organische Chemie, Universität Würzburg, Am Hubland, 97074 Würzburg

We present measurements of the electron-transfer properties of a polyradical consisting of alternating triarylamine donor and triarylmethyl radical acceptor moieties. This first polymeric neutral mixed-valence compound is attractive for applications due to its low band gap. It shows an intervalence charge transfer (IVCT) band in the near infrared. The polyradical and a reference monomer were investigated by liquid-phase fs pump–probe spectroscopy in two different solvents. Excited in the visible spectral range and probed with a whitelight supercontinuum, the transient spectra of the polyradical feature two bands around 550 nm and 650 nm. These bands are assigned to characteristic transitions of the anion and the radical cation, respectively, formed upon optically induced electron transfer. The decay curves exhibit a biexponential decay in the ps time regime. The short-living – solvent dependent – component refers to the direct decay from the IVCT state to the ground state. The long-living – solvent independent – component is tentatively attributed to an equilibrium formation of the IVCT state and a completely charge-separated state.