In Situ GIWAXS Analysis of Solvent and Additive Effects on PTB7 Thin Film Microstructure Evolution during Spin Coating

Eric F. Manley, Joseph Strzalka, Thomas J. Fauvell, Nicholas E. Jackson, Matthew J. Leonardi, Nicholas D. Eastham, Tobin J. Marks, Lin X. Chen

Research output: Contribution to journalArticle

34 Citations (Scopus)

Abstract

The influence of solvent and processing additives on the pathways and rates of crystalline morphology formation for spin-coated semiconducting PTB7 (poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)-carbonyl]-thieno[3,4-b]thiophenediyl]]) thin films is investigated by in situ grazing incidence wide-angle X-ray scattering (GIWAXS) and optical reflectance, to better understand polymer solar cell (PSC) optimization approaches. In situ characterization of PTB7 film formation from chloroform (CF), chlorobenzene (CB), and 1,2-dichlorobenzene (DCB) solutions, as well as CB solutions with 1% and 3% v/v of the processing additives 1-chloronapthalene (CN), diphenylether (DPE), and 1,8-diiodooctane (DIO), reveals multiple crystallization pathways with: (i) single-solvent systems exhibiting rapid (<3 s) crystallization after a solvent boiling point-dependent film thinning transition, (ii) solvent + additive systems exhibiting different crystallization pathways and crystallite formation times from minutes (CN, DPE) to 1.5 h (DIO). Identifying crystalline intermediates has implications for bulk-heterojunction PSC morphology optimization via optimized spin-casting processes.

Original languageEnglish
Article number1703933
JournalAdvanced Materials
Volume29
Issue number43
DOIs
Publication statusPublished - Nov 20 2017

Keywords

  • PTB7
  • additives
  • in situ GIWAXS
  • organic photovoltaics
  • spin coating

ASJC Scopus subject areas

  • Materials Science(all)
  • Mechanics of Materials
  • Mechanical Engineering

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    Manley, E. F., Strzalka, J., Fauvell, T. J., Jackson, N. E., Leonardi, M. J., Eastham, N. D., Marks, T. J., & Chen, L. X. (2017). In Situ GIWAXS Analysis of Solvent and Additive Effects on PTB7 Thin Film Microstructure Evolution during Spin Coating. Advanced Materials, 29(43), [1703933]. https://doi.org/10.1002/adma.201703933