Invsetigation on High Charge Density of States in Electrocheimcal Polymer Transistor

Abstract

Using temperature-dependent charge transport measurements, we investigated spectral density of states (DOS) in the bandgap of polythiophene thin-films under high carrier densities (< 3.5 x 10^20 cm-3) induced by electrochemical doping. The thermally activated charge transport indicates that the electrical currents in the polymer thin-film under high charge density state follows the Meyer-Neldel rule. The spectral DOS extracted from the electrolyte-gated polymer film lie in the range of 8.0 x 10^19 cm-3eV-1 ~ 8.0 x 10^21 cm-3eV-1, which are at least two orders of magnitude larger than the DOS extracted from the same polymer film at relatively low induced carrier densities by general oxide dielectrics. This is believed to result from the complete passivation of trap sites distributed in the polymer thin-film bulks by the high carrier density induced in the device. By using such a method, DOS distributions close to the intrinsic energy distribution of the polythiophenethin-film could be estimated.