Applied Physics A

, Volume 95, Issue 1, pp 291–296

Polaron and ion diffusion in a poly(3-hexylthiophene) thin-film transistor gated with polymer electrolyte dielectric

Article

DOI: 10.1007/s00339-008-5026-9

Cite this article as:
Mills, T., Kaake, L.G. & Zhu, X. Appl. Phys. A (2009) 95: 291. doi:10.1007/s00339-008-5026-9

Abstract

Electrolytes are finding applications as dielectric materials in low-voltage organic thin-film transistors (OTFT). The presence of mobile ions in these materials (polymer electrolytes or ion gels) gives rise to very high capacitance (>10 μF/cm2) and thus low transistor turn-on voltage. In order to establish fundamental limits in switching speeds of electrolyte gated OFETs, we carry out in situ optical spectroscopy measurement of a poly(3-hexylthiophene) (P3HT) OTFT gated with a LiClO4:poly(ethyleneoxide) (PEO) dielectric. Based on spectroscopic signatures of molecular vibrations and polaron transitions, we quantitatively determine charge carrier concentration and diffusion constants. We find two distinctively different regions: at VG≥−1.5 V, drift-diffusion (parallel to the semiconductor/dielectric interface) of hole-polarons in P3HT controls charging of the device; at VG<−1.5 V, electrochemical doping of the entire P3HT film occurs and charging is controlled by drift/diffusion (perpendicular to the interface) of ClO4 counter ions into the polymer semiconductor.

PACS

85.30.Tv82.35.Rs66.30.Hs82.45.Gj72.80.Le

Copyright information

© Springer-Verlag 2008

Authors and Affiliations

  1. 1.Department of ChemistryUniversity of MinnesotaMinneapolisUSA