White polymer phosphorescent light-emitting devices with a new yellow-emitting iridium complex doped into polyfluorene

A new yellow-emitting iridium complex Ir(3-piq)2pt with 3-phenylisoquinoline(3-piq) as cyclometalated ligand by introducing 2-(2H-1,2,4-triazol-3-yl)pyridine (pt) as ancillary ligand was synthesized. Efficient yellow polymer light-emitting devices (PLEDs) with the new iridium complex Ir(3-piq)2pt in device structure ITO/PEDOT/PVK/Ir-complex (x%):PFO (or +PBD (30%))/Ba/Al (with or without PBD electron transports additive) were fabricated. The device doped with 4% Ir(3-piq)2pt displayed a quantum efficiency of 9.4% (16.2 cd/A) at 5.06 mA/cm2 with PBD additive. A white emission was also obtained at a doping concentration of 0.5% Ir(3-piq)2pt with no PBD added. CIE coordinate (0.34 and 0.31) close to National Television Standards Committee (NTSC) white standard, external quantum efficiency of 2.25%, and luminance of 2250 cd/m2 at applied voltage of 15 V were obtained. The results indicated that introducing triazole group based ancillary ligand into iridium complexes could enhance the electron-transporting ability of the iridium complexes.