In Situ Analysis of Solvent and Additive Effects on Film Morphology Evolution in Spin-Cast Small-Molecule and Polymer Photovoltaic Materials

Eric F. Manley, Joseph Strzalka, Thomas J. Fauvell, Tobin J. Marks, Lin X. Chen

Research output: Contribution to journalArticle

8 Citations (Scopus)

Abstract

To elucidate the details of film morphology/order evolution during spin-coating, solvent and additive effects are systematically investigated for three representative organic solar cell (OSC) active layer materials using combined in situ grazing incidence wide angle x-ray scattering (GIWAXS) and optical reflectance. Two archetypical semiconducting donor (p-type) polymers, P3HT and PTB7, and semiconducting donor small-molecule, p-DTS(FBTTh2)2 are studied using three neat solvents (chloroform, chlorobenzene, 1,2-dichlorobenzene) and four processing additives (1-chloronaphthalene, diphenyl ether, 1,8-diiodooctane, and 1,6-diiodohexane). In situ GIWAXS identifies several trends: 1) for neat solvents, rapid crystallization occurs that risks kinetically locking the material into multiple crystal structures or crystalline orientations; and 2) for solvent + additive processed films, morphology evolution involves sequential transformations on timescales ranging from seconds to hours, with key divergences dependent on additive/semiconductor molecular interactions. When π-planes dominate the additive/semiconductor interactions, both polymers and small molecule films follow similar evolutions, completing in 1–5 min. When side chains dominate the additive/semiconductor interactions, polymer film maturation times are up to 9 h, while initial crystallization times <10 s are observed for small-molecule films. This study offers guiding information on OSC donor intermediate morphologies, evolution timescales, and divergent evolutions that can inform OSC manufacture.

Original languageEnglish
Article number1800611
JournalAdvanced Energy Materials
Volume8
Issue number23
DOIs
Publication statusPublished - Aug 16 2018

Keywords

  • additives
  • in situ GIWAXS
  • organic solar cells
  • polymer
  • spin-coating

ASJC Scopus subject areas

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

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