Dresden 2011 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 8: Poster: Organic Semiconductors
CPP 8.23: Poster
Monday, March 14, 2011, 17:30–19:30, P2
Influence of substrate heating on excited state generation rates and lifetime in organic solar cells studied by photoinduced absorption spectroscopy — •Hannah Ziehlke1, Christian Koerner1, Roland Fitzner2, Egon Reinold2, Peter Bäuerle2, Karl Leo1, and Moritz Riede1 — 1IAPP, TU Dresden — 2Institut für Organische Chemie II und Neue Materialien, Uni Ulm
The performance of organic solar cells crucially depends on the separation of photogenerated excitons into free charge carriers. The dissociation process is sensitively influenced by the nanomorphology of donor (D) and acceptor (A) phases in the photoactive blend layer. Closed percolation paths have to be present such that the created charges are able to leave the blend layer, but also the crystallinity of the D- and the A-phase influence exciton dissociation on a molecular scale. Substrate heating during the vacuum deposition of the active layer is a method to influence the thin film morphology that can lead to improved device performance. We here characterize dicyanovinyl capped quinquethiophenes (D) deposited on substrates at different temperatures (30 and 80∘ C). Photoinduced absorption spectroscopy (PIA) is used to determine excited state lifetimes and generation rates.We find that efficient charge separation occurs in blends with C60 (A) and identify the observed excited states as donor cations and triplet excitons. Heating the substrate results in an increased lifetime of the donor cation on the one hand and a decrease in the generation rate of cations on the other hand. The PIA results are complemented by solar cell devices as well as morphological studies.