Robust Processing of Small-Molecule:Fullerene Organic Solar Cells via Use of Nucleating Agents

Neil D. Treat, Obadiah G. Reid, Sarah Fearn, Garry Rumbles, Craig J. Hawker, Michael L. Chabinyc, Natalie Stingelin

Research output: Contribution to journalArticle

Abstract

The power conversion efficiency (PCE) of small-molecule bulk heterojunction solar cells is highly sensitive to the "ink" formulation used to produce the photoactive layer. Here we demonstrate that the addition of nucleating agents renders device fabrication notably less susceptible to the ink composition, promising a route toward more robust processing of efficient devices over large areas and enabling more facile materials screening. We selected as a model system blends of 7,7-[4,4-bis(2-ethylhexyl)-4H-silolo[3,2-b:4,5-b]dithiophene-2,6-diyl]bis[6-fluoro-4-(5-hexyl-[2,2-bithiophen]-5-yl)benzo[c][1,2,5]thiadiazole](p-DTS(FBTTh2)2) as the donor and [6,6]-phenyl C71-butyric acid methyl ester (PC71BM) as the acceptor because this is one of the small-molecule OPV blends with a device performance that is most sensitive to ink formulation, especially when used with the processing aid diiodooctane (DIO). Addition of DIO is essential to obtain high device performances; however, a notable increase in device performance is only achieved over a very narrow DIO content regime. Use of nucleating agents drastically changes this situation and leads to well-performing devices even at extreme levels of DIO. We thus start to address here one of the great challenges in organic solar cell research: the fact that, too often, only a very limited composition range leads to high efficiency devices. This means that for every new donor or acceptor a multitude of formulations have to be tested, including in combination with processing aids, to ensure that promising materials are not overlooked. The use of nucleating agents, thus, promises to render materials discovery more straightforward as this dependency of device performance with composition can be reduced.

Original languageEnglish
Pages (from-to)1973-1980
Number of pages8
JournalACS Applied Energy Materials
Volume1
Issue number5
DOIs
Publication statusPublished - May 29 2018

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Keywords

  • device yield
  • nucleating agents
  • organic solar cells
  • processing aids
  • processing reproducibility
  • small-molecule:fullerene blends

ASJC Scopus subject areas

  • Chemical Engineering (miscellaneous)
  • Energy Engineering and Power Technology
  • Electrochemistry
  • Materials Chemistry
  • Electrical and Electronic Engineering

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