Fabrication of High Performance Organic Thin Film Transistor Arrays and Application to 5-inch Flexible Displays

Abstract

AbstractWe have demonstrated a 5-inch flexible color liquid crystal display (LCD) and organic light emitting display (OLED) driven by low-voltage operation organic TFT. In order to achieve high-quality and high-resolution moving images, OTFTs with high performances such as a high mobility, high ON/OFF ratio, low sub-threshold slope (SS) and low operating voltage, are developed. We fabricated pentacene-based low-voltage operation OTFT with a Ta2O5 gate dielectric prepared at a low temperature process. The resulting OTFT array showed a high mobility of 0.3-0.4 cm2/Vs, ON/OFF ratio over 107, VTH=2.7V, and low SS=0.3 V/decade. OTFTs with solution-processable materials such as fluoropolymer gate dielectric and liquid-crystalline semiconducting polymers, PBTTT, were also investigated. Electrical characteristics and stabilities of these devices will be discussed. In the final section, we will demonstrate OTFT-driven flexible displays. Both of the flexible LC device and the OLED device were successfully integrated on the pentacene-based OTFT arrays. Printing and lamination techniques were introduced to assemble the flexible LC device. Phosphorescent polymer materials, which can be patterned by ink-jet printing, were used for emitting layer of OLED. Color moving images were successively shown on the resulting 5-inch displays using an active-matrix driving technique of the OTFT at a low driving voltage of 15V.