Influence of Solvent Additive 1,8-Octanedithiol on P3HT:PCBM Solar Cells

Weijia Wang, Lin Song, David Magerl, Daniel Moseguí González, Volker Körstgens, Martine Philipp, Jean François Moulin, Peter Müller-Buschbaum

Research output: Contribution to journalArticlepeer-review

44 Scopus citations

Abstract

Processing solvent additives in polymer:fullerene bulk heterojunction systems are known as a promising method to enhance photovoltaic performance. It is generally agreed that solvent additives enable polymers to have a high degree of molecular order which increases the device performance. However, the understanding of the efficiency enhancement is not complete. There is a lack of insight regarding the quantitative determination of the molecular miscibility between polymer and fullerene as well as the inner morphology changes induced by the additives. In this work, understanding of the influence of the solvent additive 1,8-octanedithiol (ODT) is provided on the classic system poly(3-hexylthiophene-2,5-diyl):[6,6]-phenyl-C61 butyric acid methyl ester (P3HT:PCBM) films. The impact on polymer crystallinity, surface structure, inner morphology, and quantitative molecular miscibility of P3HT and PCBM is studied as a function of ODT volume concentration. The crystallinity is probed with absorption spectroscopy and grazing incidence wide-angle X-ray scattering. The morphology and miscibility are characterized via atomic force microscopy and time-of-flight grazing incidence small angle neutron scattering. Besides an increased crystallinity and prominent phase separation, ODT increases the solubility of PCBM in P3HT and reduces the size of amorphous P3HT domains. Moreover, solvent processing with a high ODT concentration alters the vertical material composition of the active layer.

Original languageEnglish
Article number1800209
JournalAdvanced Functional Materials
Volume28
Issue number20
DOIs
StatePublished - 16 May 2018

Keywords

  • TOF-GISANS
  • crystallinity
  • morphology
  • organic photovoltaics
  • solvent additives

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