Open AccessMicrofluidic Crystal Engineering of π-Conjugated Polymers
Author(s) -
Gang Wang,
Nils Persson,
Ping-Hsun Chu,
Nabil Kleinhenz,
Boyi Fu,
Mincheol Chang,
Nabankur Deb,
Yimin Mao,
Hongzhi Wang,
Martha A. Grover,
Elsa Reichmanis
Publication year - 2015
Publication title -
acs nano
Language(s) - Uncategorized
Resource type - Journals
SCImago Journal Rank - 5.554
H-Index - 382
eISSN - 1936-086X
pISSN - 1936-0851
DOI - 10.1021/acsnano.5b02582
Subject(s) - materials science , polymer , stacking , conjugated system , microfluidics , crystallization , volumetric flow rate , electron mobility , nanotechnology , crystallization of polymers , chemical engineering , optoelectronics , exciton , chemical physics , organic chemistry , chemistry , composite material , physics , engineering , quantum mechanics
Very few studies have reported oriented crystallization of conjugated polymers directly in solution. Here, solution crystallization of conjugated polymers in a microfluidic system is found to produce tightly π-stacked fibers with commensurate improved charge transport characteristics. For poly(3-hexylthiophene) (P3HT) films, processing under flow caused exciton bandwidth to decrease from 140 to 25 meV, π-π stacking distance to decrease from 3.93 to 3.72 Å and hole mobility to increase from an average of 0.013 to 0.16 cm(2) V(-1) s(-1), vs films spin-coated from pristine, untreated solutions. Variation of the flow rate affected thin-film structure and properties, with an intermediate flow rate of 0.25 m s(-1) yielding the optimal π-π stacking distance and mobility. The flow process included sequential cooling followed by low-dose ultraviolet irradiation that promoted growth of conjugated polymer fibers. Image analysis coupled with mechanistic interpretation supports the supposition that "tie chains" provide for charge transport pathways between nanoaggregated structures. The "microfluidic flow enhanced semiconducting polymer crystal engineering" was also successfully applied to a representative electron transport polymer and a nonhalogenated solvent. The process can be applied as a general strategy and is expected to facilitate the fabrication of high-performance electrically active polymer devices.