Berlin 2012 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 58: Focus Session: Structure and Transport in Organic Photovoltaics III (jointly with CPP)

HL 58.3: Talk

Wednesday, March 28, 2012, 15:30–15:45, ER 270

Field-dependent Charge Carrier Generation, Recombination and Extraction in Polymer Based Solar Cells — •Juliane Kniepert, Ilja Lange, James Blakesley, and Dieter Neher — Universität Potsdam, Institut für Physik und Astronomie

Recently we used the time-delayed collection field (TDCF) method to show that charge generation in solvent annealed P3HT:PCBM solar cells is independent of the electric field[1]. In these blends solvent or thermal annealing leads to a phase-separated morphology and the corresponding solar cells exhibit high values for the external quantum efficiency and fill factor. By contrast, non-treated devices show significantly lower currents and fill factors.

A fundamental understanding of the processes leading to high fill factors and currents is of great importance for the development of a new generation of high efficiency polymer solar cells.

Here, we apply bias-dependent TDCF measurements to probe the generation and recombination of charge carriers in pristine and thermally annealed devices spincast from chloroform. In conjunction with numerical modelling, we show that the differences in the I-V characteristics are not caused by field-dependent dissociation or by the enhanced recombination in non-treated blends, but rather by more efficient extraction of holes in the annealed blend.

[1] J. Kniepert et al., J. Phys. Chem. Lett. 2, 700 (2011)