Color Tuning of the OLEDs Using the Ir Complexes of White Emission by Adjusting the Band Gap of Host Materials

摘要

We have reported white organic light-emitting diodes (WOLEDs) based on single white dopants, Ir(pq)2(F2-ppy) and Ir(F2-ppy)2(pq). It was found that the similar phosphorescent lifetime of two ligands led to emit luminescence in two ligands at die same time and the emission wavelength of single white dopants had a broad peak and emit white color without the intennolecular energy transfer. The configuration of fabricated WOLEDs was 4,4', 4"-tris[ 2-naphthylphenylamino]triphenyl-amine (2-TNATA) (60 nm)/4, 4'-bis[N-(naphthyl)-Af-phenyl-amino] biphenyl (NPB) (20 nm)/ 10% IT complex doped in 4, 4, N, N'-dicarbazolebiphenyl (CBP) (30 nm )/bathocuproine (BCP) (10 nm )/tris-( 8hydroxyquinoline) aluminum (Alq3) (20 mn)/lithium quinolate (Liq) (2 nm)/Al (100 nm), where Ir(pq)2(F2ppy) and Ir(F2-ppy)2(pq) were used as white dopant, respectively. However, emission color of fabricated devices was reddish because the energy was not transferred efficiently from the CBP to the F2-ppy tigand due to the small band gap of the CBP. Therefore, we used 1, 4-phenylenesis (triphenylsilane) (UGH2) of large band gap instead of CBP as host material. As a result, high efficient OLED of white emission was fabricated for device with h-(F2-ppy)2(pq). Furthermore, The luminous efficiency of device with Ir(F2-ppy)2(pq) doped in UGH2 was about 11 cd/A at 0.06 cd/m2.