Abstract
In this thesis, we have used silk fibroin as the gate dielectric layer and CuPc as the p-type semiconductor material to fabricate organic thin-film transistors (OTFTs). Experimental parameters include the substrate temperature during thermal deposition, CuPc thickness and the passivation layer. When the depositing substrate temperature is 90℃ and the thickness of CuPc is 45nm, a field-effect mobility value of 0.96 cm2V-1s-1, an on/off ratio of ca. 1.1x103 and a threshold voltage of -2.08V are achieved. AFM and GIXRD were used to characterize the CuPc thin film. The morphology of the CuPc thin film strongly depends on temperature, specifically in the grain size and shape. At 30℃, the CuPc grains are needle-like. When the temperature increases to 90℃, the CuPc grains become rod-like. When CuPc is deposted on silk fibroin, the degree of crystallization of CuPc thin film is better than that on the untreated SiO2. TTC was used as the passivation layer to reduce the hysteresis loop and to increase the stability of the device. Ambipolar OTFTs with a bilayer of CuPc and F16CuPc was also fabricated. A bilayer of 45nm CuPc/ 30nm F16CuPc exhibits the best performance of ambipolar characteristics. The field-effect mobilities of electrons and holes are 0.14 and 0.03 cm2V-1s-1 respectively. With the assistance of the TTC passivation layer, 45 nm CuPc/ 17 nm F16CuPc ambipolar exhibits better ambipolar characteristics. The field-effect mobilities of electrons and holes are 0.035 and 0.47 cm2V-1s-1 respectively.