The Influence Of Degradable Silk Fibroin On The Performance Of Organic Field-effect Transistors

Organic field-effect transistors(OFETs) have attracted considerable attention for their potential applications in electronic devices such as radio-frequency identification(RFID) tags, flexible electronic circuit and sensors due to their light-weight, low-cost and compatible with flexible substrate. In this thesis, OFET based on silk fibroin(SF) was chosen as the research subject, the main purpose is to obtain high performance OFET. We mainly studied the influence of the SF dielectric layer on the performance of device and the sensitivity of ultraviolet light and also the flexible and degradation features of SF substrate device. Specific contents are shown as follows:1. Pentacene OFET consisted of SF dielectric layer was studied. By using poly(methyl methacrylate)(PMMA) and SF as the dielectric layer, OFET based on single or double layer dielectrics were investigated. Compared with these based on single PMMA or SF dielectric or SF/PMMA bilayer dielectric devices, OFET with biocompatible PMMA/SF bilayer dielectric exhibited optimal performances with a high field-effect mobility of 0.21 cm2/Vs and a current on/off ratio of 1.5×104. The performance enhancement is mainly attributed to the crystallization improvement of pentacene and the less interface trap density at the dielectric/organic interface. Meanwhile, a low contact resistance also indicated that a good electrode/organic contact was formed, thereby assisting the performance improvement of OFET.2. Ultraviolet(UV) sensitive characteristic of PMMA/SF bilayer dielectric OFET was investigated. On the basis of the preparation of the high performance OFET based on PMMA/SF bilayer dielectric, the UV sensitive characteristics of such devices were researched. Compared with single PMMA dielectric layer devices, the results showed that the responsivity of PMMA/SF bilayer dielectric devices reached to 1.1 A/W, which was 3 folds as much as the single PMMA dielectric device. This phenomenon is due to the change of interface of both active layer and dielectric layer.3. Flexible and degradation characteristics of OFET based on SF substrate was analysized. SF substrate with a thickness of ca. 60 μm was fabricated by using its good mechanical properties and film forming capability. The OFETs with SF substrate were fabricated. A combined investigation of structural and electrical properties indicated that the device had favorable deformation characteristics. The device presented a perfect stability with 12.4 % field effect mobility(μ) decrease but 4 folds current on/off current ratio increase after 1000 times compressive stress bends, while the device had no mechanical damage and the device shape remained unchanged. This indicated that SF is a good substrate material. Besides, we also took the degradation property into consideration, and the results showed that the SF substrate could completely degradation in water. This work paved the way by using degradable SF material to fabricate envioenmentally friendly and disposable optoelectronic and electronic devices.