Polaron recombination in pristine and annealed bulk heterojunction solar cells

We determined the dominant polaron recombination loss mechanism in pristine and annealed polythiophene:fullerene blend solar cells by applying the photoinduced charge extraction by linearly increasing voltage method in dependence on temperature. In pristine samples, we find a strongly temperature-dependent bimolecular polaron recombination rate, which is reduced as compared to the Langevin theory. For the annealed sample, we observe a polaron decay rate which follows a third order of carrier concentration almost temperature independently. (C) 2008 American Institute of Physics. [DOI: 10.1063/1.3005593].