The effect of air exposure on device performance of flexible C8-BTBT organic thin-film transistors with hygroscopic insulators

Abstract

Organic thin film transistors (OTFTs) are normally sensitive to ambient conditions and show performance degradation in air. On the contrary, the performance of flexible 2,7-dioctyl[1] benzothieno [3,2-b][1]benzothiophene (C8-BTBT) OTFTs using cross-linked polymer layer, poly(4-vinyl-phenol)-4,4′-(hexafluoroisopropylidene) diphthalic anhydride (PVP-HDA), as the dielectric layer can be improved in air conditions with 40% relative humidity. Under soaking in air with 40% relative humidity, the electrical behavior, surface morphology, and contact angle of the flexible C8-BTBT OTFTs using PVP-HAD as dielectric layer with three different thicknesses were investigated. It is found that, when the devices with 375 nm-thick PVP-HDA films are placed in 40% relative humidity air conditions for 6 h, the corrected average mobility (μ) can increase from 3.2 to 5.1 cm2 V−1 s−1. Furthermore, the average threshold voltage (Vth) changes from −12.4 to −9.3 V while keeping a constant ratio of Ion/Ioff = 104. These results indicate that the flexible C8-BTBT OTFTs with PVP-HDA dielectric layer exhibit interesting application prospects.