Berlin 2012 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 18: Organic semiconductors I
CPP 18.3: Talk
Wednesday, March 28, 2012, 10:00–10:15, C 130
Does conjugation help exciton dissociation? A study on poly(p-phenylene)s in planar heterojunctions with C60 or TNF — •Christian Schwarz1, Heinz Bässler1, Irene Bauer1, Jan-Moritz Koenen2, Eduard Preis2, Ullrich Scherf2, and Anna Köhler1 — 1Experimental Physics II, University of Bayreuth — 2Macromolecular Chemistry, Bergische Universität Wuppertal
We report the field-assisted photocurrent generation in organic bilayer diodes with different poly(p-phenylene)s as donors and C60 or TNF as acceptor. The polymers differ regarding their torsional degree of freedom and concomitantly regarding their conjugation length and energetic disorder. We find the photocurrent yield to saturate around 100 % at fields between 5 · 104 V/cm to 106 V/cm. The saturation field required scales with the optical gap, implying that conjugation and energetic order is of crucial importance for the yield. We conclude that the rate limiting step for photogeneration is the formation of a loosely bound electron-hole pair that can either be collected by a moderate field or relax back to a tightly bound electron-hole pair.