Berlin 2012 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 6: Poster: Structural Ordering and Electronic Transport (joint focus with HL)
CPP 6.17: Poster
Montag, 26. März 2012, 17:30–19:30, Poster A
Role of Structural Order on Ultrafast Free Charge Generation in Polythiophene/Si Photovoltaics — •Christina Scharsich1, Daniel Herrmann2, Sabrina Niesar3, Martin Stutzmann3, Eberhard Riedle2, and Anna Köhler1 — 1Universität Bayreuth — 2Ludwig-Maximilians-Universität München — 3Technische Universität München
In hybrid and organic solar cells, the precise process for the generation of free charge carriers is still not fully understood. This is partially due to the ultrafast time scale of a few-10 fs on which charge transfer between e-donor and acceptor takes place. Here, we use a novel broadband ultrafast transient absorption spectroscopy with a time resolution of 40 fs to probe charge generation and recombination in thin films of poly(3-hexylthiophene)/silicon (P3HT/Si). The fundamental photophysical processes accompanying charge generation depend strongly on morphology of the heterojunction. For this reason, we study the role of structural order on the ultrafast charge generation by applying regioregular (rr) and regiorandom (rra) P3HT as electron donor material. [1,2] We show that singlet excitons dissociate to subsequently form polarons within 140 fs. Aggregated rrP3HT/Si films show recombination of non-geminate pairs. In comparison, geminate recombination appears to be the dominant loss mechanism for rraP3HT/Si films. Therefore, we find that polymer structural order is the key criterion for free charge generation in hybrid P3HT/Si solar cells.
[1] D. Herrmann et al. J. Am. Chem. Soc. 2011, 133, 18220-18233 [2] C. Scharsich et al. J. Polym. Sci., Part B: Polym. Phys. - in press