OLED Emitting Layer Composition for Viewing Angle and Color Purity
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Solution Overview
Problem
Existing organic light emitting diodes (OLEDs) face challenges in achieving high efficiency while maintaining excellent viewing angle characteristics and color purity.
Innovation Solution
Incorporating two hosts with a difference in ground state dipole moment values of 1.5 Debye or more in the light emitting layer, allowing for increased full width at half maximum and controlled color purity, thereby enhancing the viewing angle and color rendering index.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single host material is used in the light emitting layer, then the device structure is simple, but the viewing angle characteristics are poor
Solution Approach 1:
The patent uses a composite host system consisting of a first host material and a second host material with different dipole moments. This composite approach broadens the emission spectrum to improve viewing angle characteristics while maintaining device functionality. The first host material (e.g., mCP) provides a baseline emission profile, while the second host material (e.g., TCTA or TAPC) with a larger dipole moment contributes to spectrum broadening, achieving excellent viewing angle performance without excessive structural complexity.
2Illumination intensity
If the full width at half maximum is increased to improve viewing angle, then the color purity deteriorates
Solution Approach 1:
The patent applies local quality by using a dopant material with specific optical properties embedded within the composite host system. The dopant (e.g., Ir(ppy)3 for green emission) provides narrow, pure color emission at specific wavelengths, while the composite hosts broaden the overall spectrum. This allows the system to simultaneously achieve broad spectrum coverage for viewing angle and narrow emission lines for color purity, as the dopant's localized emission properties are preserved within the broader host matrix.
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 solution results in improved viewing angle characteristics and color purity, increasing the selection of materials for higher light emitting efficiency and performance.
Implementation Method 1
The principle of the organic light emission phenomenon is as follows. When an organic material layer is disposed between an anode and a cathode, if voltage is applied between the two electrodes, electrons and holes are injected into the organic material layer from the cathode and the anode, respectively. The electrons and the holes which are injected into the organic material layer are recombined to form an exciton, and the exciton falls down again to the ground state to emit light.
Implementation Method 2
In the light emitting layer, a first host material and a second host material different from each other in a ground state dipole moment are used. The difference between a ground state dipole moment value of the first host material and a ground state dipole moment value of the second host material is 1.5 Debye or more. This configuration increases the full width at half maximum of the light emitting spectrum, thereby improving viewing angle characteristics.
Data Source
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AI summary
The present specification relates to an organic light emitting diode.