Berlin 2012 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 18: Organic semiconductors I

CPP 18.5: Talk

Wednesday, March 28, 2012, 10:30–10:45, C 130

Exciton and Charge Dynamics in PCPDTBT:PCBM Blends Probed by Broadband VIS-NIR Transient Absorption Spectroscopy — •Fabian Etzold, Ian A. Howard, Don Cho, Michael Meister, Ralf Mauer, Klaus Müllen, and Frédéric Laquai — MPI für Polymerforschung Mainz

The efficiency of PCPDTBT:PCBM bulk heterojunction solar cells depends very much on the film preparation conditions, like the use of cosolvents, for reasons still not well understood. In this contribution we present the exciton and charge carrier dynamics in pristine PCPDTBT films and in photovoltaic blends with PCBM studied by VIS-NIR broadband transient absorption spectroscopy. In particular we monitor the previously unobserved, but for low-bandgap polymers essential spectral region between 1000-2000 nm, where we can clearly identify the individual contributions and dynamics of singlet excitons, charge-transfer excitons as well as free and trapped polarons. This not only allows a qualitative assessment of the effect of cosolvents on the photophysics, but also the extraction of the most relevant recombination parameters that finally determine the device efficiency. Our experiments show that cosolvents promote the generation of mobile charge carriers that can be extracted as photocurrent.

[1] F. Etzold et al., manuscript in preparation.