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Durham University

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Publication details for Professor Andy Monkman

HOLLAND, ER, BLOOR, D, MONKMAN, AP, BROWN, A, DELEEUW, D, BOUMAN, MM & MEIJER, EW (1994). EFFECTS OF ORDER AND DISORDER ON FIELD-EFFECT MOBILITIES MEASURED ON CONJUGATED POLYMER THIN-FILM TRANSISTORS. Journal Of Applied Physics 75(12): 7954-7958.
  • Publication type: Journal Article
  • ISSN/ISBN: 0021-8979
  • Keywords: POLYDIACETYLENES; OLIGOMERS; CHROMISM

Author(s) from Durham

Abstract

The morphology of conjugated polymer thin films has been controlled by
exploiting the processes giving rise to solvatochromism in the initial
polymer solutions from which the polymer films were deposited by spin
coating. The material used was the substituted polythiophene,
3[2(S2-methylbutoxy)ethyl]-polythiophene. Starting with polymer
dissolved in ''good'' solvent, various quantities of ''bad'' solvent
when added lead to the reorganization of the solubilizing side chains
attached to the conjugated polymer backbone. Ordering of these side
chains increases with addition of bad solvent decreasing the
flexibility of the backbone, yielding more rigid rodlike polymer
chains. This in turn causes aggregation and finally precipitation. It
is found that this molecular order can be transferred from solution to
solid film during the spinning process, ascertained from optical
spectroscopy. With these films acting as the active layer in a
field-effect transistor structure, the mobility of the carriers
injected into the films can be measured. It is found that as the
molecular order and aggregation increases, carrier mobility decreases
from approximately 10(-5) cm-2 V-1 S-1 to less-than-or-equal-to 10(-8)
cm2 V-1 s-1 in films displaying the highest degree of molecular order.
This is ascribed to the increased interchain separation in the ordered
systems along with effects due to macroscopic aggregate grain
boundaries.