Benzoxazole Derivative Host Material for OLED Driving Voltage
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Solution Overview
Problem
Current light-emitting elements using phosphorescent compounds face challenges with high driving voltage due to the need for host materials with high triplet excitation energy and poor hole/electron transport capabilities, limiting emission efficiency and increasing power consumption.
Innovation Solution
Development of benzoxazole derivatives with high triplet excitation energy and bipolar properties, suitable for use as host materials in light-emitting layers, enhancing both emission efficiency and reducing driving voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If host materials with high triplet excitation energy are used in light-emitting elements using phosphorescent compounds, then emission efficiency is improved, but driving voltage increases due to poor hole/electron transport capabilities
Solution Approach 1:
The patent changes the chemical structure parameters of the host material by introducing bipolar carbazole units combined with electron-transporting moieties (oxadiazole, triazole, pyrimidine, pyridine rings). This structural modification simultaneously optimizes multiple parameters: triplet excitation energy for efficient phosphorescent compound activation and charge transport properties for reduced driving voltage
Solution Approach 2:
The patent creates composite host materials by combining carbazole units with electron-transporting moieties in a single molecular structure. This composite approach integrates the high triplet excitation energy characteristic of carbazole with the excellent electron and hole transport properties of the heterocyclic moieties, resolving the contradiction between emission efficiency and driving voltage
2Productivity
If phosphorescent compounds are dispersed in host material to suppress concentration quenching, then emission efficiency is improved, but the host material requires high triplet excitation energy which limits material selection
Solution Approach 1:
The patent modifies the host material structure to have triplet excitation energy higher than common phosphorescent compounds (Ir(ppy)3 at 2.4 eV, PtOEP at 2.3 eV) by combining carbazole units with electron-transporting moieties. This parameter optimization expands material selection flexibility while maintaining high emission efficiency
Solution Approach 2:
The patent designs host materials with multi-functional characteristics: high triplet excitation energy for phosphorescent compound activation, bipolar charge transport capability, and structural versatility to accommodate different phosphorescent compounds. This makes the host material universally applicable to various phosphorescent emitters
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 use of benzoxazole derivatives as host materials in light-emitting elements improves current efficiency and reduces power consumption, achieving low driving voltage and high emission efficiency.
Implementation Method 1
a substance having high excitation energy, particularly as a substance having high triplet excitation energy
Implementation Method 2
by application of a voltage to a light-emitting element, electrons and holes are injected into a layer including the light-emitting organic compound from a pair of electrodes, whereby a current flows. Then, carriers (i.e., electrons and holes) recombine to place the light-emitting organic compound into an excited state. The light-emitting organic compound returns to a ground state from the excited state, thereby emitting light.
Implementation Method 3
by using a compound that converts a triplet excited state into luminescence (hereinafter referred to as a phosphorescent compound), internal quantum efficiency can be improved from 75 to 100% theoretically
Data Source
AI summary
Disclosed is a novel benzoxazole derivative which has high excitation energy, particularly high triplet excitation energy, and is a bipolar substance. A benzoxazole derivative represented by the following General Formula (G1) is provided.In the formula, R1 and R2 independently represent a hydrogen atom, an alkyl group with 1 to 4 carbon atoms, or a substituted or unsubstituted aryl group with 6 to 13 carbon atoms, substituents of the substituted aryl group may be bonded to form a ring which may form a spiro ring structure, R11 to R14 independently represent a hydrogen atom, a halogen, an alkyl group with 1 to 4 carbon atoms, or an unsubstituted aryl group with 6 to 10 carbon atoms, a bond formed between any two of α, β, and γ forms a carbazole skeleton, and n is 0 to 3.