Dresden 2009 – wissenschaftliches Programm

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SYOP: Symposium Organic Photovoltaics: From Single Molecules to Devices

SYOP 4: Organic Photovoltaics: from Single Molecules to Devices

SYOP 4.45: Poster

Donnerstag, 26. März 2009, 16:30–19:00, P1A

Probing ultrafast charge transfer dynamics in a P3HT:PCBM blend via photoluminescence quenching — •Theo Hoyer¹, Stefan Trotzky², Wilfried Tuszynski¹, Christoph Lienau¹, and Jürgen Parisi¹ — ¹Institut für Physik, Carl von Ossietzky Universität Oldenburg, 26111 Oldenburg, Germany — ²Institut für Physik, Johannes Gutenberg-Universität, 55099 Mainz, Germany

So far the ultrafast charge transfer dynamics in polymer/fullerene blends for solar cell device applications have mostly been studied by nonlinear photoinduced absorption techniques. Time-resolved photoluminescence (PL) methods have the potential to yield additional information about the charge separation dynamics as they give direct access to the exciton relaxation dynamics and provide higher sensitivity.

Here, we present an experimental study of the donor-acceptor charge transfer in a polymer/fullerene blend by means of a femtosecond PL up-conversion technique. The exciton dynamics of pristine P3HT and a P3HT:PCBM blend with a weight ratio of 1:1 were measured by recording PL decay traces at λ = 650 nm after two-photon excitation at excitation densities of up to 6·10¹⁸ cm⁻³. Both samples show clearly nonexponential decay traces compatible with diffusion-limited exciton-exciton annihilation and charge transfer in the polymer blend. A fast PL decay in this blend on a time scale of about 150 fs indicates that about 50% of the photogenerated excitons undergo a prompt charge transfer process.