Electrical characterization of the pentacene based organic field effect transistors deposited on various gate insulators

In this thesis, thermal evaporated pentacene active layer was deposited on various gate insulators to fabricate organic field effect transistors (OFETs) at bottom-gate top-contact geometry. Commercially purchased polymethyl methacrylate (PMMA), polyvinyl alcohol (PVA), poly(4-vinylphenol) (PVP), polystyrene (PS), poly(4-methyl styrene) (P4MS) and poly(4-vinylphenol-co-methyl methacrylate) (PVP_co_PMMA) gate dielectrics were used to investigate the influence of gate insulator on the OFETs performance and they were prepared by sol gel spin coating method. These materials were used as gate insulators both alone and in the organic part of bilayer organic/inorganic gate insulators. As inorganic gate dielectric parts, Al2O3 insulators formed by the anodization method and TiO2 formed by the spin coating method were used in these bilayer structures. Electrical measurements of the pentacene based OFETs were performed under dark conditions. Then, the electrical characteristics of the monolayer polymer insulator based transistors were investigated under different white illumination intensities. The electrical parameters such as mobility, threshold voltage, on/off ratio, subthreshold voltage, interface trap density, photosensitivity and photoresponsivity of the fabricated OFETs were calculated.