Effect of Imbalanced Charge Transport on the Interplay of Surface and Bulk Recombination in Organic Solar Cells

A1 Journal article (refereed)


Internal Authors/Editors


Publication Details

List of Authors: Dorothea Scheunemann, Sebastian Wilken, Oskar J. Sandberg, Ronald Österbacka, Manuela Schiek
Publisher: AMER PHYSICAL SOC
Publication year: 2019
Journal: Physical Review Applied
Journal acronym: PHYS REV APPL
Volume number: 11
Issue number: 5
Number of pages: 10
ISSN: 2331-7019


Abstract

Surface recombination has a major impact on the open-circuit voltage (V-OC) of organic photovoltaics. Here, we study how this loss mechanism is influenced by imbalanced charge transport in the photoactive layer. As a model system, we use organic solar cells with a 2 orders-of-magnitude-higher electron than hole mobility. We find that small variations in the work function of the anode have a strong effect on the light-intensity dependence of V-OC. Transient measurements and drift-diffusion simulations reveal that this is due to a change in the surface recombination rather than the bulk recombination. We use our numerical model to generalize these findings and determine the circumstances under which the effect of contacts is stronger or weaker compared to the idealized case of balanced charge transport. Finally, we derive analytical expressions for V-OC in the case that a pile-up of space charge is present due to highly imbalanced mobilities.


Keywords

Charge recombination, Charge transport, Organic solar cells


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Last updated on 2020-01-04 at 08:33