Hybrid bilayer gate dielectric-based organic thin film transistors

Abstract

Organic thin film transistors (OTFTs) are key building blocks for flexible, low cost electronics systems. They provide a viable alternative for silicon-based electronics with added advantages of low cost and flexibility. However, few issues like high-operating voltage, low-switching speed, high-leakage current and reliability are still a challenge. The overall performance of an OTFT depends on organic semiconductors and gate dielectric interface. In this paper, we review the current status and trends in the choice of dielectric layer for OTFTs. As a starting point, the performance parameters of an OTFT and their dependence on the dielectric layer are briefly discussed. A variety of dielectric materials which includes high-k inorganic, organic, surface coated inorganics and nanocomposites are also presented. The advantages and drawbacks of each of these materials are discussed in detail. We reviewed the latest developments in the dielectric materials especially, self-assembled monolayers (SAMs), hybrid bilayers and nanocomposites. SAM-based OTFTs offer several advantages but shift in the threshold voltage remains a concern. Nanocomposites are a latest addition to the dielectric materials, which offer advantages like solution processing and improved dielectric constant but have a rough surface. A hybrid bilayer that incorporates the inorganic dielectric as a base layer and a thin polymer layer over it to improve the surface properties offers several desirable characteristics over the other choices. Hence, we propose that hybrid bilayer gate dielectrics shall play a pivotal role in improving the OTFT performance.

Self-Assembled Nanodielectrics for Solution-Processed Top-Gate Amorphous IGZO Thin-Film Transistors

“…The average saturation mobility of the printed devices, 20 cm 2 V –1 s –1 , is very similar to that achieved in the current work and further demonstrates the integrity of both the solution-processed a-IGZO and Hf-SAND-4 in a top-gate device configuration, despite the more complex fabrication process . For the present top-gate a-IGZO/Hf-SAND-4 devices, the average threshold voltage ( V th ) is 0.83 ± 0.04 V, and the small operating voltage range (−1.5 to 2.5 V) is suitable for most technological applications. ,,, The present TFTs also exhibit low gate leakage currents with maxima in the mid-10 –10 A range. The average log­( I on : I off ) and SS for the top-gate devices are 4.26 ± 0.31 and 293 ± 22 mV/dec (eq S1), respectively.…”

“…13 For the present top-gate a-IGZO/Hf-SAND-4 devices, the average threshold voltage (V th ) is 0.83 ± 0.04 V, and the small operating voltage range (−1.5 to 2.5 V) is suitable for most technological applications. 6,8,13,35 The present TFTs also exhibit low gate leakage currents with maxima in the mid-10 −10 A range. The average log(I on :I off ) and SS for the top-gate devices are 4.26 ± 0.31 and 293 ± 22 mV/dec (eq S1), respectively.…”

Systematic Analysis of Self-Assembled Nanodielectric Architecture and Organization Effects on Organic Transistor Switching

“…Organic electronics have attracted significant activity in both fundamental research and technology development for several decades. − This reflects the potential of organic devices for solution-processing entire device architectures via high-throughput printing, which eliminates the need for photolithography, significantly reducing the production times and lowering the costs. , Additionally, organic devices can enable low-temperature processing compared with traditional silicon and most conventional metal oxide-based electronics, thereby allowing deposition on plastic substrates. This opens the door to flexible and even stretchable devices .…”

“…This opens the door to flexible and even stretchable devices . The applications for these high-throughput-derived products include smart windows, , wearable electronics, , radio frequency identification tags, , and diverse (bio)­sensors. ,− …”

“…Despite the many promising qualities of organic semiconductors, there are currently several significant limitations. Compared to metal-oxide semiconductors, organic semiconductors have significantly lower field-effect mobilities and drain currents, thus requiring higher operating voltages . Since the turn-on voltage ( V on ) is the voltage at which a device is operational, a lower V on or threshold voltage ( V th ) means lower operating voltages and reduced energy consumption .…”