Effect of a high boiling point additive on the morphology of solution-processed P3HT-fullerene blends

Yun Long, Alexander J. Ward, Arvydas Ruseckas, Ifor David William Samuel

Research output: Contribution to journalArticlepeer-review

11 Citations (Scopus)
1 Downloads (Pure)

Abstract

The use of high boiling point additives in solution processing has been widely employed to control the active layer morphology in bulk heterojunction organic solar cells. The morphology of the heterojunction is crucial in controlling charge separation and extraction by the electrodes, and therefore the power conversion efficiency (PCE) of the device. This paper presents a study of time-resolved fluorescence quenching in blends of P3HT containing varying concentrations of the fullerenes PC61BM or PC71BM. The relationship between the fluorescence quenching rate and fullerene concentration indicates that the fullerene molecules are dispersed within the P3HT film for up to 5% by mass of fullerene. For higher fullerene concentrations, the additional fullerene molecules aggregate and form fullerene domains. The high degree of phase segregation observed in these blends is beneficial for solar cell performance because the segregated fullerene phase provides electron percolation pathways through the blend. The addition of 1,8-diiodooctane (DIO) to the solutions for spin coating into films changes the scale of fullerene segregation when the ratio by mass of fullerene exceeds 20%. At high fullerene concentrations the rate of fluorescence quenching decreases in P3HT:PC61BM blends when prepared with DIO indicating a larger scale phase separation. The effect of DIO on the morphology of P3HT:PC71BM blends is the opposite in that it causes faster quenching in the blends. Overall the results show that DIO can be used to control the morphology of photovoltaic blends of P3HT with fullerenes.
Original languageEnglish
Pages (from-to)23-30
Number of pages8
JournalSynthetic Metals
Volume216
Early online date25 Jan 2016
DOIs
Publication statusPublished - Jun 2016

Keywords

  • Organic solar cells
  • OPV
  • Conjugated polymers
  • Bulk heterojunction
  • Fluorescence quenching
  • Exciton harvesting

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