Dresden 2017 – wissenschaftliches Programm
CPP 41.5: Vortrag
Mittwoch, 22. März 2017, 16:15–16:30, ZEU 260
Recombination Dynamics and the Role of Space Charge Effects in Organic Photovoltaics — •Martin Stolterfoht1, Ardalan Armin2, Safa Shoaee1, Bronson Philippa3, Paul Meredith2, and Dieter Neher1 — 1University of Potsdam, Potsdam-Golm, Germany — 2The University of Queensland, Brisbane, Australia — 3James Cook University, Cairns, Australia
The origin of photocurrent losses in the power-generating regime of organic solar cells (OSCs) remains a controversial topic, although recent literature suggests the importance of bimolecular recombination in determining the bias dependence of the photocurrent. Here we studied the steady-state recombination dynamics in OSCs with different hole mobilities from short-circuit to maximum power point (Adv. Energy Mater. DOI: 10.1002/aenm.201601379). We show that in this bias regime, first-order recombination outweighs bimolecular recombination of free charges. We demonstrate that the first-order losses increase with decreasing slower carrier mobility and attribute them to recombination of photogenerated and injected charges and/or geminate recombination. We also present how the competition between bimolecular recombination and extraction can be described using a simple figure of merit under consideration of space charge effects (J. Phys. Chem. Lett. DOI: 10.1021/acs.jpclett.6b02106). The experimental results obtained on 25 different OSCs represent a conclusive understanding of bimolecular recombination and allow to minimize these losses for given device parameters. Nevertheless, more work is necessary to understand the recombination losses in the power-generating regime in full generality.