Characteristics of OTFTs Using Olefin-polymer Gate Insulator and Their Application to a 5-in. OTFT-driven Flexible AMOLE
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Characteristics of OTFTs Using Olefin-polymer Gate Insulator and Their Application to a 5-in. OTFT-driven Flexible AMOLED Display Yoshiki Nakajima1, Yoshihide Fujisaki1, Tatsuya Takei1, Hiroto Sato1, Mitsuru Nakata1, Mitsunori Suzuki1, Hirohiko Fukagawa1, Genichi Motomura1, Takahisa Shimizu1, Koichi Sugitani2, Yukie Isogai2, Takeyoshi Katoh2, Toshihiro Yamamoto1, Hideo Fujikake1 and Shizuo Tokito1* 1 Science and Technology Research Laboratories, Japan Broadcasting Corporation (NHK), 1-1011, Kinuta, Setagaya-Ku, Tokyo, 157-8510, Japan. 2 R & D Center, ZEON Corporation, 1-2-1, Yako, Kawasaki-ku, Kawasaki, Kanagawa, 210-9507, Japan. * Present address: Faculty of Engineering, Yamagata University, 4-3-16 Jonan, Yonezawa-shi Yamagata, 992-8510, Japan. ABSTRACT Organic thin-film transistors (OTFTs) using cross-linked olefin polymer as a gate insulator were fabricated on a plastic film. An olefin polymer layer was formed by spin-coating and baking at temperatures below 150°C. Pentacene was used as an organic semiconductor layer. The fabricated OTFTs with a short 5-μm-long channel showed a mobility of 0.1-0.2 cm2/Vs and a current ON/OFF ratio of 107. These OTFTs also exhibited good stable performance in the atmosphere. On the basis of the results, we fabricated a 5 inches OTFT-driven flexible activematrix organic light emitting diode (AMOLED) display. The gate insulator, some metal wirings and electrodes on the OTFT backplane were formed on the plastic film by photolithography. After fabrication of the OTFT backplane, OLED layers were formed by vacuum deposition through a shadow-mask. Clear color moving images were observed on the flexible display even when it was bent. INTRODUCTION Organic thin-film transistors (OTFTs), which can be fabricated on a plastic film at low temperature, have attracted considerable attention for their application to low-cost and large-area electronic devices [1]. Recently, many prototypes using OTFTs were fabricated; for example, electronic circuits, various sensors, and flexible displays [2-5]. In the case of displays, various organic materials such as gate insulators of OTFTs, planarization and passivation layers on the backplane are required for integrating some devices on the plastic film at low process temperature. Olefin polymer has many kinds of derivatives, and its characteristics can be improved by exchanging some components of the polymer. By selecting the optimum polymer structure, an olefin polymer layer can also be formed at temperatures below 150°C. This layer exhibits a flat surface, good electrical insulation properties, and process compatibility. In this study, we report characteristics and an application of OTFTs on the plastic film. OTFTs using olefin polymer as the gate insulator were fabricated. Electrical characteristics and stability of these OTFTs were evaluated. On the basis of the results, we demonstrated a 5 inches (5-in.) OTFT-driven flexible active-matrix organic light emitting diode (AMOLED) display. Maximum process temperature of the flexible OTFT backplane was 130°C
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