Extremely efficient flexible organic light-emitting diodes with modified graphene anode

• DOI: 10.1038/nphoton.2011.318
• Publication Date: 2012-01-10T10:09:40Z
• Authors: Tae-Hee Han; Youngbin Lee; Mi-Ri Choi; Seong-Hoon Woo; Sang-Hoon Bae; Byung Hee Hong; Jong-Hyun Ahn; Tae-Woo Lee
• Keywords: DEVICES; ELECTRODES; OXIDE; 02 engineering and technology; FILMS; 7. Clean energy; TRANSPARENT; TRANSPARENT ELECTRODES; LARGE-AREA; CELLS; INJECTION; OPTOELECTRONICS; 0210 nano-technology

Although graphene films have a strong potential to replace indium tin oxide anodes in organic light-emitting diodes (OLEDs), to date, the luminous efficiency of OLEDs with graphene anodes has been limited by a lack of efficient methods to improve the low work function and reduce the sheet resistance of graphene films to the levels required for electrodes1,2,3,4. Here, we fabricate flexible OLEDs by modifying the graphene anode to have a high work function and low sheet resistance, and thus achieve extremely high luminous efficiencies (37.2 lm W–1 in fluorescent OLEDs, 102.7 lm W–1 in phosphorescent OLEDs), which are significantly higher than those of optimized devices with an indium tin oxide anode (24.1 lm W–1 in fluorescent OLEDs, 85.6 lm W–1 in phosphorescent OLEDs). We also fabricate flexible white OLED lighting devices using the graphene anode. These results demonstrate the great potential of graphene anodes for use in a wide variety of high-performance flexible organic optoelectronics. By replacing conventional indium tin oxide (ITO) anodes with high-work-function, low-sheet-resistance graphene anodes, researchers demonstrate flexible fluorescent organic LEDs with extremely high luminous efficiencies of 37.2 lm W–1 for fluorescent devices and 102.7 lm W–1 for phosphorescent devices. These values are significantly higher than those of optimized organic LEDs based on ITO anodes.