The polymer gate dielectrics and source-drain electrodes on n-type pentacene-based organic field-effect transistors

Pentacene-based organic field-effect transistors (OFETs) with different polymer gate dielectrics, such as polyvinyl alcohol (PVA), poly 4-vinyl phenol (PVP), and polystyrene (PS), are fabricated to study the influence of polymer dielectrics on the formation of the n-type conduction (electron) channel in the pentacene active layer. The output characteristics of OFETs and capacitance–voltage measurements indicate that the formation of n-type conduction channel in the active layer is hindered by the electron traps at the contact interface with PVP dielectric layers, probably due to the high dissociation constant of protons of the hydroxyl groups in PVP. The dissociated protons at PVP dielectric layer form the electron traps and restrict the formation of n-type conduction channel. In comparison, OFETs applying PVA of relatively lower dissociation constant than that of PVP as the gate dielectric present the decent n-type output characteristics. The appropriate work function of source-drain electrodes as well as a trap-free dielectric layer are essentially important to determine the performance of pentacene-based n-type OFETs. The pentacene-based OFETs applying calcium as the source-drain electrodes and PS as the dielectric layer has the electron mobility of 0.077 cm2s−1V−1 in this study.