Red Phosphorescent Compound for OELDs with High Color Purity
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Solution Overview
Problem
Current red phosphorescent compounds for organic electroluminescent devices (OELDs) face challenges in achieving high luminescence efficiency and color purity while maintaining low power consumption, as higher color purity leads to decreased relative spectral sensitivity and luminance efficiency.
Innovation Solution
A red phosphorescent compound with a host material capable of transporting electrons or holes, and a dopant material represented by specific chemical formulas, where the phenylquinoline ligand of the iridium complex is substituted with methyl, cyclohexyl, or other groups to enhance steric hindrance and prevent quenching effects, improving luminescent efficiency and color purity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the color purity of red phosphorescent material is increased, then the color purity of OELD is improved, but the relative spectral sensitivity and luminance efficiency decrease
Solution Approach 1:
The patent modifies the chemical structure of phosphorescent materials by changing ligand types (from bipyridine to phenylquinoline), metal centers (Ir, Pt, Os), and substituent groups (methyl, cyclohexyl, fluorine, chlorine) to adjust emission characteristics. This structural parameter change enables achieving high color purity (x>0.64) while maintaining acceptable luminance efficiency by optimizing the balance between color purity and energy utilization through molecular design
Solution Approach 2:
The patent employs composite phosphorescent materials combining different metal complexes (Ir, Pt, Os) with various organic ligands (phenylquinoline, bipyridine, carbene) and substituent groups. These composite structures allow simultaneous optimization of color purity and luminance efficiency by leveraging the complementary properties of different components, achieving high color purity without complete sacrifice of efficiency
2Power
If the luminescence efficiency is increased, then the brightness of OELD is improved, but the power consumption increases
Solution Approach 1:
The patent optimizes the ratio of triplet to singlet excitons by modifying molecular structure (using heavy metal atoms Ir, Pt, Os to enhance spin-orbit coupling) and adjusting host-guest interactions in the emitting layer. This enables higher luminescence efficiency from triplet excitons (which constitute 75% of excitons) without proportionally increasing power consumption, as the improved efficiency converts more excitons into useful light
Solution Approach 2:
The patent converts the typically harmful non-radiative decay of triplet excitons into beneficial phosphorescent emission. By using heavy metal complexes with strong spin-orbit coupling, the patent transforms the 75% triplet excitons (which would normally be lost) into useful light emission, achieving high luminescence efficiency while managing power consumption through improved exciton utilization
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The proposed red phosphorescent compound achieves high luminescence efficiency, high color purity, and reduced power consumption, enabling OELDs to operate with high brightness and internal quantum efficiency, driven by relatively low power, thereby reducing power consumption.
Implementation Method 1
The present application is directed to a red phosphorescent compound and an organic electroluminescent device (OELD) and more particularly to a red phosphorescent compound having high color purity and high luminescent efficiency
Implementation Method 2
a host material being capable of transporting an electron or a hole
Implementation Method 3
The OELD emits light by injecting electrons from a cathode and holes from an anode into an emission compound layer, combining the electrons with the holes, generating an exciton, and transforming the exciton from an excited state to a ground state
Data Source
AI summary
A red phosphorescent compound includes a host material being capable of transporting an electron or a hole; and a dopant material represented by following Formula 1:wherein theis one ofand each of R1 to R4 is one of the group consisting of hydrogen atom (H), C1 to C6 substituted or non-substituted alkyl group, C1 to C6 substituted or non-substituted alkoxy group, and halogen atom.