Low voltage organic field-effect transistors prepared with crosslinked poly(vinyl alcohol) (cr-PVA) as gate dielectric and either poly(3-hexylthiophene-2,5-diyl) (P3HT) or Copper Phthalocyanine as channel semiconductor material usually exhibit low field-effect mobility. It is known that the interface of the cr-PVA with the channel semiconductor has defects (charged sites or dipoles), which impose constraints to the charge transport from source to drain along the channel, degrading transistor operational performance. Our research group investigated different cr-PVA surface modification procedures aiming at the passivation, suppression or at least assuage of the deleterious effects introduced by the interface defects. As a result of the treatments, we observed a general improvement of the transistor characteristics, with incremented field-effect charge carrier mobility, transconductance, output resistance, on/off current ratio and reduced subthreshold swing. In order to monitor the interface vicinity, we measured the field-effect mobility of the charge carriers flowing along the channel as a function of the effective channel bottleneck thickness near to the source. Adopting this procedure, we demonstrate that the modification of the gate insulator/channel semiconductor interface leads to a significant increase of field effect mobility in the immediacy of the interface. Our results demonstrate that the used treatments constitute a simple but efficient strategy to improve overall organic field-effect transistor performance.
Ivo A.Hümmelgen was born in 1963 in São Bento do Sul, Brazil. He completed his PhD degree in Physics at the University of Göttingen, Germany, in 1991, working with Prof. Wolfgang Schröter, investigating electronic states associated to one-dimensional defects in compound semiconductors. Now he is Full Professor and leader of a research group on organic optoelectronic devices, at the Department of Physics, Federal University of Paraná. His major research interests are related to the investigation of charge injection and transport phenomena in organic semiconductors thin films and the application of conjugated polymers and small weight molecular materials to organic and hybrid transistors, photovoltaic devices, memories and sensors. He is topical editor of Journal of Solid State Electrochemistry, member of the advisory panel of Journal of Physics D: Applied Physics and Secretary of the Brazilian Physical Society.