Pentacene-based TTFTs with polymer gate dielectric and NiO_x electrodes

We report on the fabrication of pentacene-based transparent thin-film transistors (TTFTs) that employ pentacene, NiO_x, and poly-4-vinylphenol (PVP) for channel, source-drain (S/D) electrode, and gate dielectric, respectively. Spin-coated PVP showed decent dielectric strength (1.5 MV/cm) and constant (k = 3.9). Semitransparent NiO_x for S/D electrodes of which the work function is well matched to that of pentacene were deposited on a 50 nm thick pentacene channel by thermal evaporation of NiO powder. NiO_x, electrodes showed effective transmittance of ∼40% in the visible range along with good sheet resistance of ∼60 Ω/□. Our pentacene-based TTFT exhibited a field effect mobility as large as 0.07 cm²/V s in the dark, and an on/off current ratio of 10⁵. Our work demonstrates that spin-coated PVP and thermal evaporated NiO _x are promising gate dielectric and S/D electrode materials for organic TTFTs, respectively.