Electrical Characteristics Of Organic Field-effect Transistors Research Articles

Low-Temperature Solution-Processed Soluble Polyimide Gate Dielectrics: From Molecular-Level Design to Electrically Stable and Flexible Organic Transistors.

Aromatic soluble polyimides (PIs) have been widely used in organic field-effect transistors (OFETs) as gate dielectric layers due to their promising features such as outstanding chemical resistance, thermal stability, low-temperature processability, and mechanical flexibility. However, the molecular structures of soluble PIs on the electrical characteristics of OFETs are not yet fully understood. In this work, the material, dielectric, and electrical properties are evaluated to systematically investigate the chemical structure effect of aromatic dianhydride and diamine monomers on the device performance. Four soluble PIs based on 4,4'-(Hexafluoroisopropylidene)diphthalic anhydride (6FDA) and 5-(2,5-Dioxotetrahydrofuryl)-3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride, in which the monomeric precursors contain different backbones, side groups, and linkages, were employed to compare the chemical structure impact. The dielectric properties, which significantly affect the charge transport and crystallinity of OSC thin films, clearly depended on the soluble PI types as well as the surface energy and the thermal stability. Furthermore, the electrical characteristic measurement and parameter extraction of OFETs based on TIPS-pentacene revealed that the 6FDA-based soluble PIs, which lead to high field-effect mobility, near-zero threshold electric field, and outstanding electrical stability under bias stress, are the most promising gate dielectric candidates. Finally, low-temperature solution-processed OFETs are successfully integrated with ultrathin flexible substrates, and they exhibit no significant electrical performance loss after mechanical flexibility tests. This work presents a step forward in the development of soluble PI gate dielectrics for flexible electronic devices with high device performance.

Effect of non-chlorinated solvents on the enhancement of field-effect mobility in dioctylbenzothienobenzothiophene-based top-gate organic transistors processed by spin coating

Abstract The use of non-chlorinated solvents for film deposition in organic field-effect transistors (OFETs) is highly desirable to fabricate flexible and printable electronic circuits by environmentally friendly processes. Here, we investigate the influence of the use of non-chlorinated solvents, such as toluene, p-xylene, cyclohexanone, and mesitylene, for the deposition of 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) films by spin coating on the morphologies of these semiconductor films and the electrical characteristics of OFETs with a top-gate configuration. The results show that the size of polycrystalline domains in spin-coated C8-BTBT films tends to increase as the boiling point (b.p.) of the solvent increases, whereas an improvement in the field-effect mobility is restricted by the decrease in the extent to which the C8-BTBT film covers the substrate due to the long evaporation time of high b.p. solvents. The addition of the high b.p. solvent p-xylene to toluene allows a significant increase in polycrystalline domain sizes in spin-coated C8-BTBT films. Further, spin coating C8-BTBT using the high b.p. solvent mesitylene at a high spin rate is effective for the production of thinner C8-BTBT films with diminished surface roughness. Top-gate C8-BTBT FETs processed by spin coating using a mixed binary solvent and by high-speed spin coating achieved high average field-effect mobilities of 4.9 and 5.4 cm2 V−1 s−1, respectively.

Enhanced performance of C60 organic field effect transistors using a tris(8-hydroxyquinoline) aluminum buffer layer

We have investigated the properties of C60-based organic field effect transistors (OFETs) with a tris(8-hydroxyquinoline) aluminum (Alq3) buffer layer inserted between the source/drain electrodes and the active material. The electrical characteristics of OFETs are improved with the insertion of Alq3 film. The peak field effect mobility is increased to 1.28 × 10−2 cm2/(V·s) and the threshold voltage is decreased to 10 V when the thickness of the Alq3 is 10 nm. The reason for the improved performance of the devices is probably due to the prevention of metal atoms diffusing into the C60 active layer and the reduction of the channel resistance in Alq3 films.