Oxadiazole Derivative Host Material for OLED Driving Voltage Reduction
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Solution Overview
Problem
Current light emitting elements using phosphorescent compounds face challenges with high driving voltage due to the poor ability of host materials like CBP to receive and transport holes and electrons, leading to inefficient light emission and high power consumption.
Innovation Solution
The development of an oxadiazole derivative with high triplet excitation energy, which acts as a bipolar substance, is used as a host material in the light emitting element to enhance the transport of holes and electrons, thereby reducing driving voltage and increasing light emitting efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If CBP is used as a host material, then triplet excitation energy is high, but driving voltage becomes high due to poor hole and electron transport ability
Solution Approach 1:
The patent employs a composite host material system consisting of CBP (host) and TCTA (guest) in specific weight ratios (5:1 to 1:5). This composite structure combines the high triplet excitation energy of CBP with the superior hole and electron transport capabilities of TCTA, thereby maintaining high energy levels while reducing driving voltage to 6V or lower.
Solution Approach 2:
The patent optimizes the weight ratio parameters of CBP and TCTA to achieve the desired balance between triplet excitation energy and charge transport. By adjusting these compositional parameters, the system achieves both high energy retention and low driving voltage operation.
2Reliability
If phosphorescent compound is dispersed in host material matrix, then concentration quenching is suppressed, but light emitting efficiency decreases due to poor carrier transport
Solution Approach 1:
The composite host system of CBP and TCTA provides both the dilution effect needed to suppress concentration quenching of phosphorescent compounds and the enhanced carrier transport properties of TCTA. This dual-function composite material simultaneously addresses quenching suppression and efficiency enhancement.
Solution Approach 2:
TCTA acts as an intermediary material that facilitates carrier transport between the phosphorescent guest molecules and the CBP host matrix. It mediates the charge transfer process, enabling efficient carrier injection while maintaining the beneficial dilution effect for quenching suppression.
3Ease of operation
If fluorescent compound is used, then light emission from singlet excited state is achieved, but internal quantum efficiency is limited to 25%
Solution Approach 1:
The patent changes the spin state parameter of the light-emitting compound from singlet (fluorescent) to triplet (phosphorescent), enabling utilization of both singlet and triplet excited states. This parameter change increases internal quantum efficiency from 25% to potentially 75-100% by harvesting triplet states through phosphorescence.
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 oxadiazole derivative enables a light emitting element with low driving voltage and high light emitting efficiency, resulting in a light emitting device with reduced power consumption and improved image quality.
Implementation Method 1
a substance which has high triplet excitation energy and can easily receive or transport both a hole and an electron (i.e. a bipolar substance) is required
Implementation Method 2
a light emitting substance is in an excited state, and light is emitted when the excited state returns to a ground state
Implementation Method 3
a compound which converts a triplet excited state into light emission (hereinafter referred to as a phosphorescent compound)
Data Source
AI summary
An oxadiazole derivative represented by the following general formula (G1) is synthesized and applied to the light emitting element,Am;wherein Am is a substituent represented by a general formula (Am1), (Am2), or (Am3); each of α, β1, and β2 represents an arylene group having 6 to 25 carbon atoms; each of Ar1 to Ar6 represents an aryl group having 6 to 25 carbon atoms; each of R1 to R3 represents hydrogen, an alkyl group having 1 to 4 carbon atoms, or an aryl group having 6 to 25 carbon atoms; and R4 represents an alkyl group having 1 to 4 carbon atoms or an aryl group having 6 to 25 carbon atoms.