Modelling of organic field effect transistors with inkjet printed poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) electrodes: study of the annealing effects.

In the present work, the transport mechanism of organic transistors with bottom-gate/top-contact structure, manufactured by employing traditional and inkjet printing techniques, was studied. Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) conductive polymer was used for realizing printed source, drain and gate electrodes. The influence of the printing parameters (substrate temperature, drop overlapping degree, drop emission frequency) on the uniformity and morphology of the PEDOT:PSS layer was investigated. Polymethyl methacrylate (PMMA) was used as organic dielectric and pentacene, deposited by thermal evaporation, was employed as p-type semiconductor. Organic field effect transistors (OFETs) were fabricated and electrically characterized before and after the thermal annealing process at 120 degrees C for 1 h in nitrogen ambient. The effect of the annealing on the performances of the OFETs was investigated by modelling the measured electrical characteristics and analyzing them in terms of mobility, characteristic temperature and energy distribution of the density of localized states (DOS). In addition, the OFET working under electrical stress in ambient conditions was observed and discussed.