Organic thin film transistors (OTFT) are excellent can- didates for large area electronics on arbitrary and flexible substrates, enabling novel flexible displays as well as wearable electronics such as artificial skin. However, enabling truly-ubiquitous electronics through OTFTs demands not only high performance and high degree of flexibility, but also a wide range of operating voltages. Applications such as electrophoretic displays, digi- tal X-ray imaging, photovoltaic systems-on-glass, and TFT-MEMS integration for large actuation are but a few that can enable high driving voltages on an OTFT technology platform.
We are currently developing a solution-processed 6,13-Bis(triisopropylsilylethynyl) pentacene (TIPS- pentacene) high-voltage, organic, thin film transistor (HVOTFT) with self-assembled monolayer (SAM) treatments that is capable of driving voltages beyond -450 V while operating with threshold voltages below -10 V. The ability to modulate such high-voltages with a relatively low gate voltage is highly appealing for future MEMS integration. The HVOTFT is defined by a dual channel architecture comprised of a gated and offset region, enabling FET and high-voltage capabilities, respectively. Furthermore, a high-k cubic pyrochlore dielectric Bi1.5Zn1Nb1.5O7 (BZN) is employed to achieve low gate leakage currents and low threshold voltages.A combination of organosilane self-assembled monolayers and a self-shearing drop cast method is used to grow thin (< 100 nm) crystal bands of TIPS- pentacene on the HVOTFT structures. Controlling the thickness of the organic semiconductor layer is critical in achieving high breakdown voltages of -450 V as well as high ION/IOFF current ratios of 104 A/A. Recent efforts in developing a self-aligned solution-process using surface energy engineering to enhance control of the crystal growth as well as to have transistor-to- transistor isolation have proven promising.