Dresden 2009 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 9: Poster 1

HL 9.92: Poster

Monday, March 23, 2009, 14:30–17:00, P2

Exciton binding energy in conjugated polymers — •Daniel Mack, Julien Gorenflot, Carsten Carsten, and Vladimir Dyakonov — Experimental Physics VI, Julius-Maximilians-University of Würzburg, , D 97074 Würzburg

One important parameter governing the efficiency of organic donor:acceptor solar cells is the open-circuit voltage. The relative energy levels of donor and acceptor are a trade-off between efficient charge transfer, i.e., exciton dissociation, and large open-circuit voltage. A deeper understanding of the exciton binding energy and factors influencing it are therefore important in view of an optimisation of the performance of organic solar cells. We studied the exciton binding energy in the conjugated polymer poly(3-hexylthiophene) by field-dependent photoluminescence (PL) quenching. A laser generates singlet excitons within the polymer matrix; an electric field is then applied in order to dissociate these excited states into electron*hole pairs. The field-induced separation of the excitons, corresponding to a reduction of ratiative recombination, is investigated by monitoring a decrease of the PL signal. Our experimental results are discussed and compared with calculations after the models of Arkhipov [1] and Emilianova [2].

[1] V. I. Arkhipov, H. Bässler, M. Deussen und E. O. Göbel, Field-induced exciton breaking in conjugated polymers. Phys. Rev. B, 52 (1995) 4932. [2] E. V. Emelianova, M. van der Auweraer, and H. Bässler, Hopping approach towards exciton dissociation in conjugated polymers. J. Chem. Phys. 128 (2008) 224709.