In this paper full polymer thin-film transistors （PTFTs） based on Poly （acrylonitrile） （PAN） as the gate dielectric and poly （2-methoxy-5-（2＇-ethyl-hexyloxy）-1,4-phenylene-vinylene） （MEH-PPV） as the semiconductor layer were investigated by using different channel width/length ratios. Relatively high dielectric constant of the polymer dielectric layer （6.27） can remarkably reduce the threshold voltage of the transistors to below -3V. Hole field-effect mobility of MEH-PPV of the PTFTs was about 4.8×10^-4cm^2/Vs, and on/off current ratio was larger than 10^2, which was comparable with that of transistors with widely used Poly （4-vinyl phenol） （PVP） or SiO2 as gate dielectrics.
