We demonstrate high-efficiency white electrophosphorescence in organic light emitting diodes (OLED) employing blue and red phosphorescent molecules. As an emitting layer, bis[2-(4,6-difluorophenyl)pyridinato-N,C2′] iridium picolinate (FIrpic) as blue and bis[2-(2′-benzo[4,5-a]thienyl)pyridinato-N,C3′]iridium (acetylacetonate) [Btp2Ir(acac)] as red phosphors were doped into a 4,4′-bis(9-carbazolyl)-2,2′-biphenyl (CBP) host. The OLED characteristics using multi-phosphors doped layers were studied. We focused on suppression of the color change with an increase of a current density while keeping high-efficiency. With an insertion of a 3 nm-thick 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) layer, high ηext of 4.9±0.5% and pure white emission of CIE (0.32, 0.33) at 10 mA/cm2 were achieved. Moreover, the color change with an increase of a current density was suppressed to a certain extent with in an insertion of other buffer layers, CBP and bis[N-(1-naphthyl)-N-phenyl]benzidine (α-NPD).
All Science Journal Classification (ASJC) codes
- Electrical and Electronic Engineering