Flexible Organic Light-Emitting Diode Displays Driven by Inkjet-Printed High-Mobility Organic Thin-Film Transistors

Abstract

A 3.2-in flexible color display, with a resolution of 50 ppi and composed of bottom-emission multiphoton organic light-emitting diodes (OLEDs) and inkjet-printed organic thin-film transistors (OTFTs) with a bottom-gate/bottom-contact structure on a color filter, was developed. The device could successfully display color videos while being bent, and achieved a maximum luminance of 125 cd/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> with white light emission. The gate dielectrics of the OTFTs used on the backplane were bilayers of cardo polymer and Parylene, and the material used for the organic semiconductors was dithieno [2,3-d;2',3'-d']benzo[1,2-b;4,5-b']dithiophene blended with polystyrene in tetralin solvent, which was coated using inkjet printing to sufficiently fill the banks composed of a fluorine-based polymer. OTFTs with a channel length of 5 μm were created using the above process, and the structure achieved a high mobility of 1.2 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> /(V·s), making it suitable for flexible color OLED displays. The mobility was about three times as high as that obtained using solution shearing methods.