| Summary: | 碩士 === 國立中正大學 === 機械工程所 === 97 === Organic thin film transistor (OTFT) has been widely studied due to its advantages of large-area and low-cost manufacture and being bendable. However, the scope of its application is still very limited because of its low carrier mobility. For example, except one recently reported device, OTFTs using semiconductive conjugated polymers never had a carrier mobility higher than 1 cm2V-1s-1. Even the mobility of the recently reported exception could only achieve 1 cm2V-1s-1.
To enhance the carrier mobility, many researches started to investigate how to improve the order of alignment of the conjugated polymers in the semiconductor layer. This thesis proposes a new approach which combines the micro-contact-printing with an alignment mechanism. The approach begins with fabrication of grooved PDMS stamps with different groove density. It is expected that when the semiconductive poly(3-hexyl thiophene) (P3HT) is spin-coated on the grooved PDMS, the polymer will align along the grooves at the same time. The aligned P3HT thin film is then printed to the substrate for fabrication of an OTFT. It was found that the OTFTs made by using the PDMS stamp with a groove density of 2400 grooves/mm did show a mobility anisotropy of 3.59 but when compared to un-controlled devices, the mobility enhancement was insignificant. The polarized UV-Visible absorption spectra, atomic force microscopy and grazing incidence x-ray diffractometer (GIXRD) were employed to understand the underlying causes. The results from polarized UV-Visible absorption spectra revealed the alignment of the P3HT along the grooves, confirming the observed mobility anisotropy. Combining these spectra results with those from the GIXRD analysis, a conjecture for the insignificant mobility enhancement was proposed.
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