Overcoming Electrode-Induced Losses in Organic Solar Cells by Tailoring a Quasi-Ohmic Contact to Fullerenes via Solution-Processed Alkali Hydroxide Layers

Zhang H, Shallcross RC, Li N, Stubhan T, Hou Y, Chen W, Ameri T, Turbiez M, Armstrong NR, Brabec C (2016)

Publication Language: English

Publication Status: Published

Publication Type: Journal article, Original article

Publication year: 2016

Journal

Book Volume: 6

Article Number: 1502195

Journal Issue: 9

DOI: 10.1002/aenm.201502195

Abstract

It is shown that the performance of inverted organic solar cells can be significantly improved by facilitating the formation of a quasi-ohmic contact via solution-processed alkali hydroxide (AOH) interlayers on top of n-type metal oxide (aluminum zinc oxide, AZO, and zinc oxide, ZnO) layers. AOHs significantly reduce the work function of metal oxides, and are further proven to effectively passivate defect states in these metal oxides. The interfacial energetics of these electron collecting contacts with a prototypical electron acceptor (C) are investigated to reveal the presence of a large interface dipole and a new interface state between the Fermi energy and the C highest occupied molecular orbital for AOH-modified AZO contacts. These novel interfacial gap states are a result of ground-state electron transfer from the metal hydroxide-functionalized AZO contact to the adsorbed molecules, which are hypothesized to be electronically hybridized with the contact. These interface states tail all the way to the Fermi energy, providing for a highly n-doped (metal-like) interfacial molecular layer. Furthermore, the strong "light-soaking" effect is no longer observed in devices with a AOH interface. Solution-processed alkali hydroxides significantly reduce the work function of metal oxides, such as zinc oxide or aluminum zinc oxide (AZO), and are further proven to effectively passivate defect states in these metal oxides. The interface states with alkali hydroxide-modified AZO contacts tail all the way to the Fermi energy, providing for a highly n-doped (metal-like) interfacial molecular layer.

Authors with CRIS profile

Additional Organisation(s)

Involved external institutions

University of Arizona United States (USA) (US) BASF Schweiz AG Switzerland (CH)

How to cite

APA:

Zhang, H., Shallcross, R.C., Li, N., Stubhan, T., Hou, Y., Chen, W.,... Brabec, C. (2016). Overcoming Electrode-Induced Losses in Organic Solar Cells by Tailoring a Quasi-Ohmic Contact to Fullerenes via Solution-Processed Alkali Hydroxide Layers. Advanced Energy Materials, 6(9). https://doi.org/10.1002/aenm.201502195

MLA:

Zhang, Hong, et al. "Overcoming Electrode-Induced Losses in Organic Solar Cells by Tailoring a Quasi-Ohmic Contact to Fullerenes via Solution-Processed Alkali Hydroxide Layers." Advanced Energy Materials 6.9 (2016).

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