High performance organic field-effect transistors

The following report presents innovative technique for surface modification and device construction of top-contact pentacene-based thin film transistors (TFTs) with saturation mobility about 2.0 cm²/Vs. In the experiment we have utilized PSPI as a modification layer presenting a non-polar interface on which the semiconductor, pentacene, could grow. The surface of the modification layers was exposed to a polarized ultraviolet light with dose ranging from 0.2 J to 8 J. Ultraviolet light was applied to achieve a non-polar surface on which high performance TFTs have been subsequently fabricated. The experimental results showed that the parasitic contact resistances of silver electrodes could be extracted by gated-transfer length method, and the corrected field-effect mobility of pentacene TFTs for linear region was as high as 2.25 cm²/Vs. In this study, we were able to control the surface energy of polymer-based gate dielectric layers and the surface energy of the PSPI layer increasing the energy from about 38 to 42 mJ/m² by differentiating doses of polarized ultraviolet light. When the PSPI film was exposed to 1 J of polarized ultraviolet light, the surface energy of PSPI, measured by the contact angle method, was about 38 mJ/m². The measured energy matched the theoretically calculated surface energy of a pentacene crystal. Hence, the higher mobility OTFTs with low surface energy gate dielectric were obtained by spin-coating the PSPI as a modifier.