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

Dorothea Scheunemann, Sebastian Wilken, Oskar Sandberg, Ronald Österbacka, Manuela Schiek

Research output: Contribution to journalArticleScientificpeer-review

10 Citations (Scopus)
1 Downloads (Pure)

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.
Original languageEnglish
Article number054090
Pages (from-to)
Number of pages10
JournalPhysical Review Applied
Volume11
DOIs
Publication statusPublished - 2019
MoE publication typeA1 Journal article-refereed

Keywords

  • Charge transport
  • Charge recombination
  • Organic solar cells

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