Coumarin-Based, Electron-Trapping Iridium Complexes as Highly Efficient and Stable Phosphorescent Emitters for Organic Light-Emitting Diodes

Abstract

A new class of coumarin-based iridium tris-cyclometalated complexes has been developed. These complexes are highly emissive, with emission colors ranging from green to orange-red. Besides modification of ligand structures, color tuning was realized by incorporation of ligands with different electrochemical properties in a heteroleptic structure. The organic light-emitting diodes (OLEDs) using these compounds as emissive dopants are highly efficient and stable. Unlike other Ir(III) phosphorescent dopants, these coumarin-based Ir(III) dopants can effectively trap and transport electrons in the emissive layer.

Understanding and predicting the orientation of heteroleptic phosphors in organic light-emitting materials

“…The synthesis and photophysical properties of (bppo) 2 Ir(ppy) and (ppy) 2 Ir(bppo) have been reported previously 31 . A reaction between [Ir(bppo) 2 (µ-Cl)] 2 and ppy-H formed both (bppo) 2 Ir(ppy) and (ppy) 2 Ir(bppo) in moderate yield.…”

“…The collected fraction was precipitated from CH 2 Cl 2 and hexanes to yield 280 mg pure (bppo) 2 Ir(acac) (51%). 1 Iridium(III) bis(2-phenylpyridinate)(benzopyranopyridinone) ((ppy) 2 Ir(bppo)) and iridium(III) bis(benzopyranopyridinone) (2-phenylpyridinate) ((bppo) 2 Ir(ppy)) were synthesized by methods similar to those described in a previous report 31 Optical spectra. Ultraviolet-visible absorption spectra were recorded using a Hewlett-Packard 4853 diode array spectrometer.…”

“…These strongly π electron-deficient ligands depress the highest occupied molecular orbital energy but do not change the lowest unoccupied molecular orbital as long as the emissive state remains localized on the bppo ligand. Electrochemistry of Ir(ppy) 2 (bppo) has been reported previously 31 .…”

Synthesis and Luminescence Studies of the Platinum Complexes Chelated with Coumarin Ligands

“…The organic electroluminescent materials have been intensely applied in the past two decades [1][2][3]. In an organic light emitting diode (OLED) device, both singlet and triplet excitons are generated in about 1 to 3 ratio by charge recombination [2].…”

Synthesis, crystal structure and photoluminescence of iridium (III) coumarin complexes

“…In OLED devices based on phosphorescent materials, both singlet and triplet excitons can be harvested for ligowing to intersystem crossing of the singlet excited states to the triplet states, 100% internal quantum efficiency can be obtained [10,11]. Highly efficient electrophosphorescent OLEDs have been reported by using Ir (III) complexes and Pt (II) complexes [10,12,13].The studies of coumarin derivatives demonstrated that they have super thermal stability and outstanding optical properties including an extended spectral response, high quantum yields, superior photostability [14][15][16][17][18][19][20][21][22][23][24][25]. Recently, we found that coumarin derivatives have a quantum yield of photoluminescence larger than 50% and good electroluminescence properties [16][17][18][19][20][21].…”