Low-voltage-operation of flexible organic C8-BTBT thin-film transistors with a reactively sputtered AlOx gate dielectric

Abstract

High-k dielectrics are frequently used for organic thin-film transistors (OTFTs), which facilitate the reduction of the device's operating voltage and enhance the total electrical performance. Along these lines, in this work, the fabrication of high-k AlOx dielectrics with high capacitance and low leakage current is proposed. On top of that, low-voltage flexible OTFTs with a solution-processed 2,7-dioctyl benzothieno[3,2-b] benzothiophene channel layer were demonstrated. The AlOx dielectric film was deposited by employing the reactive magnetron sputtering technique from a metal Al target by using a gas mixture of Ar and O2 at room temperature. At the same time, the surface morphology of the semiconductor film was optimized by controlling the solid solubility of polystyrene and polymethyl methacrylate in the semiconductor solution, which is important for improving the device performance. In this way, the prepared flexible OTFTs showed a low operating voltage of 3 V, a high switch ratio of 4.2 × 107, a high mobility is 2.39 cm2/V s, and a steep subthreshold swing close to the theoretical limit of 68 mV/decade. It is, thus, expected that this method will be applicable to the development of high-performance OTFTs.