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Title: Structural Transitions of Nanocrystalline Domains in Regioregular Poly(3-hexyl thiophene) Thin Films

Abstract

The effects of solution processing and thermal annealing on thin film morphology and crystalline structures of regioregular poly(3-hexyl thiophene) (RR P3HT) are studied in terms of molecular weight (M{sub w}). Using grazing-incidence X-ray diffraction, {pi}-conjugated planes in drop-cast films from chloroform solutions are found to be preferentially oriented parallel to the substrates regardless of M{sub w}. However, the mesoscale nanocrystalline morphology of the drop-cast films is significantly affected by M{sub w}, exhibiting a distinctive morphological transition from short nanorods to long nanofibrils above a critical number-averaged M{sub w} ({approx} 3.6 kDa). This is probably due to the change in a conformation change from an extended-chain to a folded-chain, as M{sub w} of RR P3HT increases. In contrast, spin-casting of high M{sub w} RR P3HT produces less ordered films with a lower crystallinity and mixed parallel/perpendicular orientations of {pi}-conjugated planes. The crystallinity and parallel -conjugated orientation of RR P3HT in spin-cast films could be improved by thermal treatments at high-temperatures either (1) above the glass transition temperature or (2) above the melting temperature of RR 3PHT followed by recrystallization upon cooling under vacuum. However, the charge mobility of the spin-cast films for a field-effect transistor application is still lower than thatmore » of the drop-cast films. This would be attributed to the chain oxidation and the development of distinct grain boundaries between RR P3HT nanofibrils during the thermal treatments.« less

Authors:
; ; ;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) National Synchrotron Light Source
Sponsoring Org.:
Doe - Office Of Science
OSTI Identifier:
929870
Report Number(s):
BNL-80442-2008-JA
TRN: US200822%%921
DOE Contract Number:  
DE-AC02-98CH10886
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Polymer Science Part B: Polymer Physics; Journal Volume: 45; Journal Issue: 11
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; POLYCYCLIC SULFUR HETEROCYCLES; ORGANIC POLYMERS; THIN FILMS; MORPHOLOGICAL CHANGES; NANOSTRUCTURES; MOLECULAR WEIGHT; ORIENTATION; national synchrotron light source

Citation Formats

Yang,H., Shin, T., Bao, Z., and Ryu, C.. Structural Transitions of Nanocrystalline Domains in Regioregular Poly(3-hexyl thiophene) Thin Films. United States: N. p., 2007. Web. doi:10.1002/polb.21191.
Yang,H., Shin, T., Bao, Z., & Ryu, C.. Structural Transitions of Nanocrystalline Domains in Regioregular Poly(3-hexyl thiophene) Thin Films. United States. doi:10.1002/polb.21191.
Yang,H., Shin, T., Bao, Z., and Ryu, C.. Mon . "Structural Transitions of Nanocrystalline Domains in Regioregular Poly(3-hexyl thiophene) Thin Films". United States. doi:10.1002/polb.21191.
@article{osti_929870,
title = {Structural Transitions of Nanocrystalline Domains in Regioregular Poly(3-hexyl thiophene) Thin Films},
author = {Yang,H. and Shin, T. and Bao, Z. and Ryu, C.},
abstractNote = {The effects of solution processing and thermal annealing on thin film morphology and crystalline structures of regioregular poly(3-hexyl thiophene) (RR P3HT) are studied in terms of molecular weight (M{sub w}). Using grazing-incidence X-ray diffraction, {pi}-conjugated planes in drop-cast films from chloroform solutions are found to be preferentially oriented parallel to the substrates regardless of M{sub w}. However, the mesoscale nanocrystalline morphology of the drop-cast films is significantly affected by M{sub w}, exhibiting a distinctive morphological transition from short nanorods to long nanofibrils above a critical number-averaged M{sub w} ({approx} 3.6 kDa). This is probably due to the change in a conformation change from an extended-chain to a folded-chain, as M{sub w} of RR P3HT increases. In contrast, spin-casting of high M{sub w} RR P3HT produces less ordered films with a lower crystallinity and mixed parallel/perpendicular orientations of {pi}-conjugated planes. The crystallinity and parallel -conjugated orientation of RR P3HT in spin-cast films could be improved by thermal treatments at high-temperatures either (1) above the glass transition temperature or (2) above the melting temperature of RR 3PHT followed by recrystallization upon cooling under vacuum. However, the charge mobility of the spin-cast films for a field-effect transistor application is still lower than that of the drop-cast films. This would be attributed to the chain oxidation and the development of distinct grain boundaries between RR P3HT nanofibrils during the thermal treatments.},
doi = {10.1002/polb.21191},
journal = {Journal of Polymer Science Part B: Polymer Physics},
number = 11,
volume = 45,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}