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In Situ GIWAXS Analysis of Solvent and Additive Effects on PTB7 Thin Film Microstructure Evolution during Spin Coating
Author(s) -
Manley Eric F.,
Strzalka Joseph,
Fauvell Thomas J.,
Jackson Nicholas E.,
Leonardi Matthew J.,
Eastham Nicholas D.,
Marks Tobin J.,
Chen Lin X.
Publication year - 2017
Publication title -
advanced materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.707
H-Index - 527
eISSN - 1521-4095
pISSN - 0935-9648
DOI - 10.1002/adma.201703933
Subject(s) - materials science , chlorobenzene , crystallization , chemical engineering , solvent , thin film , spin coating , crystallite , polymer chemistry , organic chemistry , nanotechnology , chemistry , engineering , metallurgy , catalysis
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.