title: The Role of Space Charge Effects on the Competition between Recombination and Extraction in Solar Cells with Low-Mobility Photoactive Layers.
abstract: The competition between charge extraction and nongeminate recombination critically determines the current-voltage characteristics of organic solar cells (OSCs) and their fill factor. As a measure of this competition, several figures of merit (FOMs) have been put forward; however, the impact of space charge effects has been either neglected, or not specifically addressed. Here we revisit recently reported FOMs and discuss the role of space charge effects on the interplay between recombination and extraction. We find that space charge effects are the primary cause for the onset of recombination in so-called non-Langevin systems, which also depends on the slower carrier mobility and recombination coefficient. The conclusions are supported with numerical calculations and experimental results of 25 different donor/acceptor OSCs with different charge transport parameters, active layer thicknesses or composition ratios. The findings represent a conclusive understanding of bimolecular recombination for drift dominated photocurrents and allow one to minimize these losses for given device parameters.
authors: Institute of Physics and Astronomy, University of Potsdam , Karl-Liebknecht-Straße 24-25, D-14476 Potsdam-Golm, Germany.|Centre for Organic Photonics & Electronics (COPE), School of Mathematics and Physics, The University of Queensland , Brisbane 4072, Australia.
authors: Martin
authors: M
authors: Stolterfoht
authors: Centre for Organic Photonics & Electronics (COPE), School of Mathematics and Physics, The University of Queensland , Brisbane 4072, Australia.
authors: Ardalan
authors: A
authors: Armin
authors: College of Science and Engineering, James Cook University , Cairns 4878, Australia.
authors: Bronson
authors: B
authors: Philippa
authors: Institute of Physics and Astronomy, University of Potsdam , Karl-Liebknecht-Straße 24-25, D-14476 Potsdam-Golm, Germany.
authors: Dieter
authors: D
authors: Neher