Production of organic field effect transistors and investigation of their performance characteristics

In this thesis a systematic study has been carried out to investigate the effect of oxide interfacial layers for the performance of organic field effect transistors. Two organic semiconductors P3HT (Poly(3-hexylthiophene–2,5-diyl)) and TIPS PENTACENE (6,13-Bis(triisopropylsilylethynyl)) with different degree of sensitivity for oxidation were studied. Moreover two different oxides, WO3 ( tungsten trioxide) and MoO3 were applied as interfacial layers in order to compare their effects on the active layers. Their thickness were varied to find the optimum thickness. It's has been observed that both oxide interlayers improve the performences of OFET's (Organic field effect transistors) based on P3HT and TIPS PENTACENE notibly mobility and thereshold voltage. Thickness dependance show that 10 nm of oxide layer is the optimum thickness which yields highest mobility and lowest threshold voltage. However, it's has been found that two oxides have very different behaviour in terms of film formation and the oxidation of the active layer. P3HT which is sensitive to oxygen get's strongly dopped by MoO3 but not with WO3. While TIPS PENTACENE which is highly resistive to oxygen didn't show such a difference. However, when WO3 and MoO3 is compared in the trnasistor characteristics, they show quiet different behaviour in terms of hysterisis for both P3HT and TIPS PENTACENE devices. Increasing the thickness of the WO3 enlarge the hysterisis continiously, where as MoO3 inclusion as interlayer removes the hysterisis. This is attribuated to their different film forming properties on the active layer.