Extremely efficient flexible organic light-emitting diodes.pdfVIP

LETTERS PUBLISHED ONLINE: 10 JANUARY 2012 | DOI: 10.1038/NPHOTON.2011.318 Extremely efficient flexible organic light-emitting diodes with modified graphene anode 1 2 1 1 2 3 Tae-Hee Han , Youngbin Lee , Mi-Ri Choi , Seong-Hoon Woo , Sang-Hoon Bae , Byung Hee Hong , Jong-Hyun Ahn2 * and Tae-Woo Lee1 * Although graphene films have a strong potential to replace Here, we demonstrate a method to increase the surface WF and indium tin oxide anodes in organic light-emitting diodes reduce the sheet resistance of graphene films to 5.95 eV and (OLEDs), to date, the luminous efficiency of OLEDs with gra- 30 V A21, respectively, by using conducting polymer compo- phene anodes has been limited by a lack of efficient methods sitions to modify the surface, thus creating a WF gradient from to improve the low work function and reduce the sheet resist- the graphene to the overlying organic layer, and by doping with ance of graphene films to the levels required for electrodes1–4. p-dopants HNO3 or AuCl3 (Supplementary Tables S4,S5). The Here, we fabricate flexible OLEDs by modifying the graphene higher WF enables holes to be injected easily into the organic anode to have a high work function and low sheet resistance, layer despite the high hole-injection barrier at the interface and thus achieve extremely high luminous efficiencies betwee