Dresden 2009 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 26: Organic Photovoltaics I

CPP 26.1: Talk

Wednesday, March 25, 2009, 14:00–14:15, ZEU 222

Efficient Polaron Pair Dissociation in Polymer:Fullerene Blends — •Carsten Deibel¹, Thomas Strobel¹, and Vladimir Dyakonov^1,2 — ¹Experimental Physics VI, Institute of Physics, Julius-Maximilians-University of Würzburg, D-97074 Würzburg — ²Bavarian Centre for Applied Energy Research e.V. (ZAE Bayern), D-97074 Würzburg

Organic bulk heterojunction solar cells already achieve energy conversion efficiencies of up to 6%. To a significant part, this is due to the very efficient separation of the bound electron–hole pairs, also called polaron pairs. This event is the intermediate but crucial step between exciton dissociation and charge transport to the electrodes. Using a simple model of Coulomb attraction of the bound charge carrier pair, the electric field needed to overcome the mutual attraction with a probability of 90% is larger than 10⁸V/m. In contrast, in good organic solar cells, almost all polaron pairs are separated at fields smaller by a factor of around 50. We attempt an explanation of this significant discrepancy by performing Monte Carlo simulations of hopping transport in a bulk heterojunction blend system. We discuss the influence of phase separation and recombination rate on the efficiency of the polaron pair dissociation.