title: Deep blue phosphorescent organic light-emitting diodes with very high brightness and efficiency.
abstract: The combination of both very high brightness and deep blue emission from phosphorescent organic light-emitting diodes (PHOLED) is required for both display and lighting applications, yet so far has not been reported. A source of this difficulty is the absence of electron/exciton blocking layers (EBL) that are compatible with the high triplet energy of the deep blue dopant and the high frontier orbital energies of hosts needed to transport charge. Here, we show that N-heterocyclic carbene (NHC) Ir(III) complexes can serve as both deep blue emitters and efficient hole-conducting EBLs. The NHC EBLs enable very high brightness (>7,800 cd m(-2)) operation, while achieving deep blue emission with colour coordinates of [0.16, 0.09], suitable for most demanding display applications. We find that both the facial and the meridional isomers of the dopant have high efficiencies that arise from the unusual properties of the NHC ligand-that is, the complexes possess a strong metal-ligand bond that destabilizes the non-radiative metal-centred ligand-field states. Our results represent an advance in blue-emitting PHOLED architectures and materials combinations that meet the requirements of many critical illumination applications.
authors.affiliation: Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan 48109, USA.
authors.forename: Jaesang
authors.initials: J
authors.lastname: Lee
authors.affiliation: Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA.
authors.forename: Hsiao-Fan
authors.initials: HF
authors.lastname: Chen
authors.affiliation: Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA.
authors.forename: Thilini
authors.initials: T
authors.lastname: Batagoda
authors.affiliation: Department of Physics, University of Michigan, Ann Arbor, Michigan 48109, USA.
authors.forename: Caleb
authors.initials: C
authors.lastname: Coburn
authors.affiliation: Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA.
authors.forename: Peter I
authors.initials: PI
authors.lastname: Djurovich
authors.affiliation: Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA.
authors.forename: Mark E
authors.initials: ME
authors.lastname: Thompson
authors.affiliation: Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan 48109, USA.|Department of Physics, University of Michigan, Ann Arbor, Michigan 48109, USA.|Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA.
authors.forename: Stephen R
authors.initials: SR
authors.lastname: Forrest