Organic thin-film transistors having inorganic/organic double gate insulators

Bottom-contact organic thin-film transistors (BC OTFTs) based on inorganic/organic double gate insulators were demonstrated. The double gate insulators consisted of tantalum pentoxide (Ta2O5) with high dielectric constant (κ) as the first gate insulator and octadecyltrichlorosilane (OTS) with low κ as the second gate insulator. The devices have carrier mobilities larger than 10−2cm2∕Vs, on/off current ratio greater than 105, and the threshold voltage of −14V, which is threefold larger field-effect mobility and an order of magnitude larger on/off current ratio than the OTFTs with a Ta2O5 gate insulator. The leakage current was decreased from 2.4×10−6 to 7.4×10−8 A due to the introduction of the OTS second dielectric layer. The results demonstrated that using inorganic/organic double insulator as the gate dielectric layer is an effective method to fabricate OTFTs with improved electric characteristics.