Characterization of ambipolar organic thin-film transistors

The top contact ambipolar organic thin-film transistors (OTFTs) and inverter based on the active layer of pentacene/C₆₀ have been fabricated. The device´s structure is glass/indium-tin oxide (ITO)/poly(methyl methacrylate) (PMMA)/pentacene/C₆₀/Ag(source/drain). We studied the effect of active layer (pentacene, C₆₀) thickness on the performance of OTFTs, and found their optimum thickness is 12 nm of pentacene and 40 nm of C₆₀, respectively. The transistor shows ambipolar transporting characteristics with the output current (I_DS) of -8.45 μ A 16.65 μA, electron and hole mobilities of 7.11×10^-2 cm²/Vs and 1.2×10^-1 cm²/Vs, respectively. Finally, an inverter has successfully been fabricated on the PET substrate based on the optimized ambipolar OTFTs. The inverter demonstrates both in the first and third quadrants with a high gain of 19 and 11.5, respectively.