Double-gate organic thin-film transistor using a photosensitive polymer as the dielectric layer

Dichromated poly (vinyl alcohol) (DCPVA) has been proposed for protecting the pentacene active layer from organic solvents such as PGMEA. DCPVA is water-soluble, and the damage to the pentacene active layer can be minimized compared to other materials dissolved in organic solvents. In this study, the dielectric properties and leakage current density of DCPVA gate dielectric samples with different ammonium dichromate (ADC) concentrations and exposure times were obtained from 6.73 to 10.5 and 6.37 × 10^{- 5} to 4.87 × 10^{- 8} (A/cm²) respectively. Also the FTIR spectroscopy was used to determine the cross-linked DCPVA films based on the relative intensity of the vibration bands of chromium(VI) and the OH group. According to FTIR, the performance of double-gate OTFTs based on blending ADC:PVA ratio of 0.25:1 film as dielectric layers of double-gate OTFT devices to exclude the acute influence of large gate leakage current caused by excess hydroxyl groups and residual Cr⁶⁺ in dielectric layer on device performance. By analyzing the electrical performance, it was found that the fabricating method of the top-dielectric layer has a great effect on the performance of double-gate OTFTs. SEM images of pentacene microstructure show significant cracks on the top of the pentacene layer due to the swelling effect of the DCPVA polymer after post-baking. Therefore, we used vacuum drying to form photosensitive DCPVA as the top-dielectric layer of a double-gate OTFT circuit array. The use of top-dielectric and electrode layers on the top of pentacene significantly increased the performance of double-gate OTFTs. In summary, we eventually demonstrate that double-gate OTFTs using a low-temperature solution process exhibited an equivalent mobility of 0.53 cm²/Vs and on-off ratio of 8 × 10³.