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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 8: Poster: Organic Semiconductors

CPP 8.6: Poster

Montag, 14. März 2011, 17:30–19:30, P2

Effect of Nongeminate Recombination on Fill Factor in Polythiophene:Methanofullerene Organic Solar Cells — •Ralf Mauer, Ian A. Howard, and Frédéric Laquai — Max Planck Institute for Polymer Research, Mainz, Germany

A key factor in solar cell efficiency is the dependence of the photocurrent on applied bias. With respect to organic solar cells, it is often suggested that this factor is governed by the field dependence of charge-transfer state separation. Here we demonstrate that this is not the case in benchmark polythiophene:methanofullerene solar cells. By examining the temperature and light intensity dependence of the current voltage characteristics we determine that: 1) the majority of free charge generation is not dependent on temperature, and 2) the competition between extraction and recombination of free charges principally determines the dependence of photocurrent on bias. These results are confirmed by direct observation of the temperature dependence of charge separation and recombination using transient absorption spectroscopy and highlight that in order to achieve optimal fill factors in organic solar cells minimizing free carrier recombination is an important consideration.