title: New iridium dopants forg white phosphorescent devices: enhancement of efficiency and color stability by an energy-harvesting layer.
abstract: A new light blue complex (fmoppy)2Ir(tfpypz) [bis(4'-fluoro-6'-methoxylphenyl pyridinato)-iridium(III)-3-(trifluoromethyl)-5-(pyridin-2-yl)-1,2,4-triazolate] and a new orange complex (dpiq)2Ir(acac) [bis(3,4-diphenylisoquinoline)-iridium(III)-acetylacetonate] were synthesized. These two complexes were used as the dopants for the fabrication of two-element white phosphorescent devices. Via the introduction of a thin energy-harvesting layer (EHL) to harvest the extra energy and exciton from the emission zone, highly efficient two-element white devices with excellent color stability were created. One of the best devices shows yellow-white color emission with an extremely high external quantum efficiency (EQE) of 21.5% and a current efficiency of 68.8 cd/A. The other device gave a pure white emission with an external quantum efficiency of 19.2% and a current efficiency of 53.2 cd/A. At a high brightness of 1000 cd/m(2), the EQE still remains as high as 18.9 and 17.2%. With a brightness of 1000-10000 cd/m(2), the CIE coordinates of these two devices shift by only (0.02, ≤0.01). The white phosphorescent devices with the EHL showed much higher efficiency and better color stability than the one without the EHL.
authors.affiliation: Department of Chemistry, National Tsing Hua University, Hsinchu 30013, Taiwan.
authors.forename: Ho-Hsiu
authors.initials: HH
authors.lastname: Chou
authors.forename: Yi-Kai
authors.initials: YK
authors.lastname: Li
authors.forename: Yu-Han
authors.initials: YH
authors.lastname: Chen
authors.forename: Ching-Chih
authors.initials: CC
authors.lastname: Chang
authors.forename: Chuang-Yi
authors.initials: CY
authors.lastname: Liao
authors.forename: Chien-Hong
authors.initials: CH
authors.lastname: Cheng