Arnold Tamayo

Saturated deep blue organic electrophosphorescence using a fluorine-free emitter

We demonstrate saturated, deep blue organic electrophosphorescence using the facial- and meridianal- isomers of the fluorine-free emitter tris(phenyl-methyl-benzimidazolyl)iridium(III)(f-Ir(pmb)3 and m-Ir(pmb)3, respectively) doped into the wide energy gap host, p-bis(triphenylsilyly)benzene (UGH2). The highest energy electrophosphorescent transition occurs at a wavelength of λ=389nm for the fac- isomer and λ=395nm for the mer- isomer. The emission chromaticity is characterized by Commission Internationale de l’Eclairage coordinates of (x=0.17,y=0.06) for both isomers. Peak quantum and power efficiencies of (2.6±0.3)% and (0.5±0.1)lm∕W and (5.8±0.6)% and (1.7±0.2)lm∕W are obtained using f-Ir(pmb)3 andm-Ir(pmb)3 respectively. This work represents a departure from previously explored, fluorinated blue phosphors, and demonstrates an efficient deep blue/near ultraviolet electrophosphorescent device.

Efficient dipyrrin-centered phosphorescence at room temperature from bis-cyclometalated iridium(III) dipyrrinato complexes.

A series of seven dipyrrin-based bis-cyclometalated Ir(III) complexes have been synthesized and characterized. All complexes display a single, irreversible oxidation wave and at least one reversible reduction wave. The electrochemical properties were found to be dominated by dipyrrin centered processes. The complexes were found to display room temperature luminescence with emission maxima ranging from 658 to 685 nm. Through systematic variation of the cyclometalating ligand and the meso substituent of the dipyrrin moiety, it was found that the observed room temperature emission was due to phosphorescence from a dipyrrin-centered triplet state with quantum efficiencies up to 11.5%. Bis-cyclometalated Ir(III) dipyrrin based organic light emitting diodes (OLEDs) display emission at 682 nm with maximum external quantum efficiencies up to 1.0%.

Cyclometalated iridium(III)-sensitized titanium dioxide solar cells

Ir(III) dyes used as sensitizers in dye-sensitized solar cells produced quantum yields approaching unity for conversion of absorbed photons to current under simulated air mass 1.0 sunlight, with current production resulting from ligand-to-ligand charge-transfer states, rather than the typical metal-to-ligand charge-transfer states in ruthenium-based cells.

22.1: Invited Paper: Color Tuning Dopants for Electrophosphorescent Devices: Toward Efficient Blue Phosphorescence from Metal Complexes

In this paper, we describe different strategies for achieving efficient blue electrophosphorescence. The first approach involves the use of ancillary ligand tuning of emission. The emissive unit is an organometallic Ir fragment, whose triplet energy is tuned by the choice of ancillary ligand. This approach is useful for making blue emitters, but luminance efficiency drops when the energy is shifted to saturated blue. The second approach described here is to shift the cyclometallated ligand from phenyl-pyridine to either a phenyl-pyrrazole or phenyl-imidazole. Both complexes emit strongly in the near UV, however, only the imidazole complex (carbene ligand) emits strongly at room temperature.

Color Tuning Dopants for Electrophosphorescent Devices: Efficient Blue Phosphorescence Pyrrazole and Carbene Complexes

In this paper, we describe several new Ir complexes for achieving efficient blue electrophosphorescence. The approach described here for achieving blue phosphorescence is to shift the cyclometallated ligand from phenyl-pyridine to either a phenyl pyrrazole or phenyl-imidazole. Both complexes emit strongly in the near UV, however, only the imidazole complex (carbene ligand) emits strongly at room temperature.