Abstract
Device characteristics of pentacene organic thin-film transistors ( OTFTs ) with silk fibroin as gate dielectric vary with relative humidity in air ambient. An encapsulation method has been developed to keep OTFTs at a fixed relative humidity. At ca. 60% relative humidity, the OTFTs exhibit a best field-effect mobility value of ca. 16.8 cm2V-1s-1 in the saturation regime and an on/off ratio of approximately three orders of magnitudes. When the relative humidity decreases to ca. 30%, filed-effect mobility decreases to ca. 4 cm2V-1s-1 and the on/off ratio reduces to approximately two orders of magnitudes. When the relative humidity increases to ca. 70%, filed-effect mobility decreases to ca. 0.28 cm2V-1s-1 and capacitance sharply increases. Device characteristics of the OTFTs depend on relative humidity. The humidity dependence of device characteristics is attributed to the change of capacitance of silk fibroin gate dielectric at different relative humidity. In the low humidity regime, quasi-static capacitance increases slowly with relative humidity. When relative humidity is about 40%~60%, quasi-static capacitance increases rapidly with relative humidity, which is strongly correlated to the better device performance at this relative humidity. When relative humidity is higher than 60%, the quasi-static capacitance extremely increases with relative humidity and decreases device performance.