[Spectral characteristics of white organic light-emitting devices based on phosphorescent system of three iridium chelates].

A white organic light-emitting device (WOLED) with a yellow phosphorescence material, bis[2-(4-tertbutylphenyl) benzothiazolato-N,C2 '] iridium (acetylacetonate) [(t-bt)2Ir(acac)], and two blue phosphorescence materials, iridium(Ill) bis (4', 6'-difluorophenylpyridinato) tetrakis(1-pyrazolyl) borate (FIr6) and bis[(4, 6-difluorophenyl)-pyridinato-N, C2 '] (picolinate) iridium (III) (FIrpic), were fabricated. Stable white emission was realized by using undoped ultrathin yellow emissive layer (EML), two doped blue EMLs together with the proper thickness of an interlayer confining the exciton. The WOLED performed pure white light emission with the Commissions Internationale de l'Eclairage (CIE) coordinates of (0.29+/-0.01, 0.34+/-0.01) from 6 to 14 V. Moreover, electroluminescence (EL) characteristics of the devices were also studied to verify the emissive mechanism from a phosphorescent system consisting of three iridium chelates. Also, the results showed that the triple-phosphor-element EMLs WOLED had lower efficiency roll-off owing to the stable recombination zone.