Beneficial Interaction between nickel oxide nanoparticles and polyethylene oxide as printable nanocomposite hole injection layer for organic solar cells
Marta Ruscello a g, Tanmoy Sarkar b, Artem Levitski b, Giovanni Maria Matrone c, Nikolaos Droseros d, Stefan Schlisske a e, Eleni Sachs a e, Patrick Reiser a f, Eric Mankel a f, Wolgang Kowalsky a g, Natalie Banerji d, Natalie Stingelin c, Gitti L. Frey b, Gerardo Hernandez-Sosa a e
a InnovationLab GmbH, Heidelberg-Germany, Speyerer Straße, 4, Heidelberg, Germany
b Department of Materials Science and Engineering, Technion – Israel Institute of Technology, Haifa 3200003, Israel
c Department of Materials, Imperial College London, United Kingdom, Prince’s Consort Road, South Kensington Campus, London, United Kingdom
d Department of Chemistry and Biochemistry, University of Bern - Switzerland, Freiestrasse, 3, Bern, Switzerland
e Light Technology Institute, Karlsruhe Institute of Technology, Engesserstr. 13, 76131 Karlsruhe, Germany
f Institute of Material Science, TU Darmstadt, 64287 Darmstadt (Germany)
g Institute for High Frequency Technology, TU Braunschweig, Speyerer Str. 4, Heidelberg, 69115, Germany
Proceedings of Interfaces in Organic and Hybrid Thin-Film Optoelectronics (INFORM)
València, Spain, 2019 March 5th - 7th
Organizers: Natalie Stingelin, Henk Bolink and Michele Sessolo
Oral, Marta Ruscello, presentation 003
DOI: https://doi.org/10.29363/nanoge.inform.2019.003
Publication date: 8th January 2019

In the field of organic electronics, rising research attention has been dedicated to the investigation of novel interlayers. A family of materials that has been deserving increasing interest for such purposes is the one of transition metal oxide nanoparticles, which can provide high quality interlayers for both charge injection or extraction. Metal oxide nanoparticles are suitable for solution-processed electronics thanks to many advantages: they can be dissolved in organic solvents and used as printable inks, can be processed at relatively low temperatures and can offer an increased stability compared to conjugated polymers. However, they also present certain technical challenges due to the higher surface to bulk ratio (i.e. surface trap states) or present problems during film formation (i.e. agglomeration).[1] For this reason, various kinds of polymers can be employed to offer a hybrid solution to these issues.

We present here the improvement of the processability of non-stoichiometric nickel oxide (NiOx) nanoparticle ink by blending with high molecular weight polyethylene oxide (PEO). Recently, NiOx has attracted increasing attention as a hole extraction layer in organic and perovskite photovoltaics due to its excellent optical transparency, p-type conductivity and good electron blocking properties. Nonetheless, the fabrication of highly efficient NiOx thin films is challenging due to the low viscosity of the inks or the high sintering temperatures of the precursor approaches. Here, we show how PEO can help dispersing the nanoparticles hindering their aggregation after deposition without compromising film functionality. Through Kelvin Probe, Contact Angle measurement, X-ray Photoelectron Spectroscopy and Transmission Electron Microscopy we observe that the presence of PEO is beneficial for a better tunability of the NiOx film thickness and morphology. We also show that such effect on the film formation is observed to be beneficial when the NiOx:PEO blends are applied as a hole extraction layer on OPV devices, improving device performance. Moreover, the inclusion of the polymer in the nanoparticle ink allows, for the first time, the inkjet-printing of the NiOx layer without requiring high temperature post-treatment. [Manuscript in preparation]

This work was financially supported by the EC through the Horizon 2020 Marie Skłodowska-Curie ITN project INFORM (Grant Agreement 675867).

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