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Alkyl Side Chain Length Modulates the Electronic Structure and Electrical Characteristics of Poly(3-alkylthiophene) Thin Films
journal contribution
posted on 2013-06-06, 00:00 authored by Hwa Sung Lee, Jeong
Ho Cho, Kilwon Cho, Yeong Don ParkThe alkyl side chain length in poly(3-alkylthiophene)
(P3AT) was
found to affect the electrical properties and molecular electronic
structures in thin films. The self-assembly and morphology of a P3AT
film was easily controlled through the solvent vapor pressure (varied
over the range 0–55 kPa) during solidification. Under high
solvent vapor pressure conditions, long dense nanowires formed in
the P3AT thin films, and the electrical properties of field-effect
transistors (FETs) based on these films improved. The enhancement
in the electrical properties of FETs based on a P3AT nanowire structure
was strongly affected by the alkyl side chain length. Alkyl side chains
in the disordered P3AT thin film act as a barrier to charge movement;
however, they assist in the self-assembly of P3AT under high solvent
vapor pressures via alkyl chain interactions. Sufficiently long alkyl
chains in P3AT molecules, however, form an insulating barrier between
the conjugated backbone and the Au electrode, thereby preventing carrier
injection and reducing the electrical characteristics of an FET device.