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 language | English (US) |
|---|---|
| Article number | 1800611 |
| Journal | Advanced Energy Materials |
| Volume | 8 |
| Issue number | 23 |
| DOIs | |
| State | Published - Aug 16 2018 |
Funding
E.F.M., T.J.F., L.X.C., and T.J.M. acknowledge financial support from the Argonne-Northwestern Solar Energy Research (ANSER) Center, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DE-SC0001059, by the U.S. Department of Energy, Office of Science, and Office of Basic Energy Sciences under Award Number DE-FG02-08ER46536. E.F.M. was also supported by the Qatar NPRP Grant 7-286-1-046. Solution scattering was performed at the DuPont-Northwestern-Dow Collaborative Access Team (DND-CAT) located at Sector 5 of the Advanced Photon Source (APS). DND-CAT is supported by the Northwestern University, E.I. DuPont de Nemours & Co., and The Dow Chemical Company. Solution scattering data were collected using an instrument funded by the National Science Foundation under Award Number 0960140. Use of the Advanced Photon Source, an Office of Science User Facility operated for the U.S. Department of Energy (DOE) Office of Science by Argonne National Laboratory, was supported by the U.S. DOE under Contract No. DE-AC02-06CH11357.
Keywords
- additives
- in situ GIWAXS
- organic solar cells
- polymer
- spin-coating
ASJC Scopus subject areas
- Renewable Energy, Sustainability and the Environment
- General Materials Science
