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

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 incident 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), diphenyl ether (DPE), and 1,8-diiodooctane (DIO), reveals multiple crystallization pathways with: i) single-solvent systems exhibiting rapid (<3s) 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 2 1.5 hours (DIO). Here, identifying crystalline intermediates has implications for bulk-heterojunction PSC morphology optimization via optimized spin-casting processes.
 [1] ;  [2] ;  [1] ;  [3] ;  [3] ;  [3] ;  [3] ; ORCiD logo [1]
  1. Northwestern Univ., Evanston, IL (United States); Argonne National Lab. (ANL), Lemont, IL (United States)
  2. Argonne National Lab. (ANL), Lemont, IL (United States)
  3. Northwestern Univ., Evanston, IL (United States)
Publication Date:
Grant/Contract Number:
AC02-06CH11357; SC0001059; FG02-08ER46536; 7-286-1-046
Accepted Manuscript
Journal Name:
Advanced Materials
Additional Journal Information:
Journal Volume: 2017; Journal ID: ISSN 0935-9648
Research Org:
Argonne National Lab. (ANL), Argonne, IL (United States); Energy Frontier Research Centers (EFRC) (United States). Argonne-Northwestern Solar Energy Research Center (ANSER)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
36 MATERIALS SCIENCE; PTB7; additive; in situ GIWAXS; organic photovoltaic; spin coating
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1398721