Gravure contact printing of flexible, high-performance polymer light emitting diodes for large-area displays and lightin
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Gravure contact printing of flexible, high-performance polymer light emitting diodes for large-area displays and lighting Alasdair J. Campbell1,3, Dae-Young Chung1,4, Jingsong Huang2,5, Dong-Seok Leem1,4, and Donal D. C. Bradley1 1
Department of Physics and the Centre of Plastic Electronics, Blackett Laboratory, Imperial College London, South Kensington campus, London, SW7 2AZ, United Kingdom 2
Molecular Vision Ltd., Imperial College BioIncubator Unit, Bessemer Building (RSM) Level 1, London, SW7 2BP, United Kingdom 3
Electronic mail: [email protected] Current address: Frontier Research Lab, Samsung Advanced Institute of Technology, Samsung Electronics, Gyeonggi-Do, 446-712, South Korea 5 Current address: Solar Press, 2 Royal College Street, London, NW1 0NH, United Kingdom 4
ABSTRACT Gravure contact printing is the highest volume, large area printing technique known. It is ideally suited for the fabrication of large-area polymer light emitting diode (PLED) based lighting, backlights and displays. Here we show how gravure can be used to fabricate the poly (3,4-ethylene dioxythiophene) : poly(styrene sulfonate) hole injection layer and the light emitting polymer emissive layer in a conventional PLED, as well as the cesium carbonate electron injection layer in an inverted PLED. The performance equals or exceeds that of devices where these layers are deposited by conventional spin-coating. INTRODUCTION Gravure contact printing is the ultra-high volume printing method conventionally used to fabricate newspapers, magazines, postage stamps and currency at speeds of up to 60 m2/s. The ability to fabricate large area organic electronic devices using this method will revolutionize consumer electronics, producing a whole range of radically new, cheap, lightweight and flexible products. In the area of organic light emitting diodes (OLEDs), key applications target areas are high-efficiency large-area lighting, high-efficiency flexible liquid crystal display (LCD) backlights, and large-area OLED based displays. Dai Nippon Printing first reported a flexible polymer light emitting diode (PLED) panel with a gravure printed light emitting polymer (LEP) layer [1]. Within the European Commission funded ROLLED project OLEDs were fabricated with gravure printed indium tin oxide (ITO) nanoparticles, poly (3,4-ethylene dioxythiophene) : poly(styrene sulfonate) (PEDOT:PSS) and LEPs [2]. Although 100 cd/m2 has been achieved, no luminousity (lm/W) or luminous efficiency (cd/A) values have been reported. Here we report on high-efficiency conventional and inverted PLEDs in which the PEDOT:PSS hole injection layer (HIL), the LEP LG1300 green emitting polyfluorene copolymer emitting layer, and the inorganic cesium carbonate electron injection layer (EIL) have been gravure printed (device structures are shown in Figure 1). The conventional PLED achieved
performance figures which equaled that of control devices with spin-coated layers. The inverted PLED exceeded the performance values of the spin-coated control devices.
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