| Summary: | 碩士 === 大同大學 === 化學工程學系(所) === 93 === The main application of organic thin film transistor is in flat organic display as driver or switching devices for organic light-emitting devices. Although organic thin film transistors have the advantages of low cost, low manufacturing temperature, being able to fabricated on flexible substrate, and being biodegradable, they suffers from high operating voltages and low electron mobility. These problems with the organic thin film transistors make them yet apply to practical applications. So in this thesis, we study the performance of OTFTs fabricated with different conditions.
We fabricate the organic thin-film transistors (OTFTs) with pentacene organic material as a active layer. This device has four layers: gate electrode, gate dielectric layer, organic active layer, and drain/source electrodes. And we used X-ray diffraction, atomic force microscope (AFM), and semiconductor parametric test system (HP 4155C) equipments to analyze the properties of organic thin film and the performance of the device. From these properties we can calculated the hole mobility and explain the possible reasons that affect hole mobility.
In the beginning, the effects of various temperatures of the substrate on the mobility and thin film properties of pentacene TFT have been investigated. It is found that the electrical characteristics of pentacene TFT depend on the temperature of substrate. The optimal mobility and on/off current ratio are 1.3 × 10 – 3 cm 2/Vs and 4.26 × 10 3 at VD = - 50 V, respectively, at substrate temperature of 80 ℃. The morphology of pentacene thin film gets smooth and crystal structure. Moreover, the mobility of pentacene OTFT increases with increasing the evaporating rate of evaporation. The best mobility, on/off current ratio, and subthreshold slope at the evaporating rate of 7 ℃/min can be obtained 5.32 × 10 – 3 cm 2/Vs, 2.26 × 10 4 and 3.99 V/decade, respectively. Finally, studies on the performance of pentacene OTFT fabricated with various temperature of the substrate. The optimal mobility, on-off current ratio, threshold voltage, and subthreshold slope of pentacene OTFT are 8.56 × 10 – 3 cm 2/Vs, 2.29 × 10 4, - 6 V, and 3.34 V/decade, respectively, with substrate temperature of 50 up to 80℃during evaporating temperature of 280 up to 350 ℃.
To summarize the result, the characteristics of device and the morphology and crystallinity of pentacene thin-film depend on significantly the temperature of substrate and evaporating rate of pentacene.
|
|---|
