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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}
}
  • Using atomic force microscopy and grazing-incidence x-ray diffraction, the authors found that the use of volatile CH2Cl2 not only offers an advantage in minimizing regioregular poly(3-hexyl thiophene) (RR P3HT) film deposition time, but also directs the desirable parallel orientation of p-p stacking planes of RR P3HT with respect to solid substrates, for both spin and drop castings. The substrate temperature effects have been investigated to support claims that the substrate-induced crystallization of RR P3HT preseeds the parallel oriented crystals prior to spin casting, when the warm CH2Cl2 solution is loaded on a 'cold' substrate held at room temperature.
  • Highlights: • SnO{sub 2} nanocrystals/thin films were fabricated on ITO glass substrate from preformed SnS thin film as sacrificial template. • The SnO{sub 2} film and SnO{sub 2}/P3HT was characterized by several techniques. • The new hybrid solar cell device was based on the hybrid thin film of SnO{sub 2} NCs and P3HT composites. - Abstract: we described a facile in-situ wet chemical method to prepare SnO{sub 2} thin film on ITO glass substrate from preformed SnS thin film as sacrificial template. The chemical conversion process of SnS to SnO{sub 2} was studied. The SnO{sub 2} film and SnO{sub 2}/P3HTmore » was characterized by several techniques, such as powder X-ray diffract meter (XRD), Raman spectrometer, scanning electron microscope (SEM), atomic force microscope (AFM) and UV–vis spectrophotometer in detail. The new SnO{sub 2}/P3HT hybrid solar cell device showed an open-circuit voltage of 0.185 V, a short-circuit current density of 0.366 mA/cm{sup 2} and a fill factor of 0.247, corresponding to a power conversion efficiency of 0.0167%.« less
  • The synthesis of regioregular poly(3-hexyl)selenophene is reported, and its optical and electrical properties are compared to those of regioregular poly(3-hexyl)thiophene.