Optimisation of diketopyrrolopyrrole: fullerene solar cell performance through control of polymer molecular weight and thermal annealing

Zhenggang Huang, Elisa Collado Fregoso, Stoichko Dimitrov, Pabitra Shakya Tuladhar, Ying Woan Soon, Hugo Bronstein, Iain Meager, Weimin Zhang, Iain McCulloch, James R. Durrant*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

23 Scopus citations

Abstract

Poly-thieno[3,2b]thiophene-diketopyrrolopyrrole-co-thiophene (DPP-TT-T) is a promising low bandgap donor polymer for organic solar cells. In this study we employ two different approaches to improve the device efficiency via optimisation of the morphology of the active layer: tuning of the molecular weight of the polymer and thermal annealing. In the former case, a higher molecular weight was found to yield a more intermixed morphology, resulting in enhanced exciton dissociation and charge separation, as confirmed by atomic force microscopy, and photoluminescence and transient absorption spectroscopies. In the later case, thermal annealing prior to metal electrode deposition increased the photon conversion efficiency to as high as 6.6%, with this enhanced efficiency being maintained even with prolonged annealing (240 hours at 80 °C). This enhancement in performance with thermal annealing was correlated with increased polymer crystallinity.

Original languageEnglish (US)
Pages (from-to)19282-19289
Number of pages8
JournalJournal of Materials Chemistry A
Volume2
Issue number45
DOIs
StatePublished - Dec 7 2014
Externally publishedYes

ASJC Scopus subject areas

  • Chemistry(all)
  • Renewable Energy, Sustainability and the Environment
  • Materials Science(all)

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