OLED Cathode Interface Layer for Low Voltage Drive
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Solution Overview
Problem
Existing organic light-emitting diode (OLED) devices face challenges in achieving high luminance efficiency while maintaining low drive voltage and color purity, particularly in producing white light with specific CIE chromaticity coordinates, and require materials that can adjust emission wavelengths for various applications.
Innovation Solution
Incorporating a layer with 10 vol% or more of a carbocyclic fused ring aromatic compound and at least one salt or complex of an alkali or alkaline earth metal between the cathode and the light-emitting layer, along with an additional layer containing an electron-withdrawing substituent, to optimize charge transport and recombination for improved efficiency and color characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If traditional organic EL devices use thick organic layers (much greater than 1 μm), then device structure is simpler, but operating voltage becomes very high (greater than 100V)
Solution Approach 1:
The patent divides the single thick organic layer into multiple thin layers (electron transporting layer, light emitting layer, hole transporting layer, each 50-200 nm thick), which reduces operating voltage while maintaining structural functionality through layered segmentation
Solution Approach 2:
The patent uses composite material structures with specific layers containing carbocyclic fused ring aromatic compounds combined with alkali/alkaline earth metal salts or complexes, creating optimized charge transport properties that reduce voltage requirements
2Ease of manufacture
If early organic EL devices used simple organic layers, then manufacturing is easier, but luminance efficiency and color stability are poor
Solution Approach 1:
The patent employs composite materials consisting of carbocyclic fused ring aromatic compounds combined with alkali or alkaline earth metal salts or complexes in specific layers, achieving high luminance efficiency and stable color characteristics while maintaining manufacturability through established deposition techniques
Solution Approach 2:
The patent assigns specific functional properties to different layers: the electron transporting layer contains carbocyclic fused ring aromatic compounds for electron mobility, the light emitting layer optimizes for luminescence, and the hole transporting layer facilitates hole injection, with each layer optimized for its specific function
3Device complexity
If conventional light-emitting materials are used, then device structure is simpler, but emission wavelength cannot be adjusted for various applications
Solution Approach 1:
The patent enables wavelength adjustment by changing the carbocyclic fused ring aromatic compound selected from specific classes (anthracene, phenanthrene, pyrene, tetracene, perylene derivatives) and modifying metal complex composition ratios, allowing emission wavelength control across different applications while maintaining device structure
Solution Approach 2:
The patent creates a universal device structure that can produce different emission wavelengths (blue, green, red, yellow, orange, white light) by simply changing the light-emitting material composition in the light emitting layer, making the same device architecture adaptable to multiple applications
4Illumination intensity
If white light is produced by combining multiple colors, then color purity improves, but achieving specific CIE chromaticity coordinates (0.33, 0.33) becomes difficult
Solution Approach 1:
The patent achieves precise CIE chromaticity coordinates (0.33, 0.33) by adjusting the composition ratios of carbocyclic fused ring aromatic compounds and metal complexes, and by controlling the thickness and composition of each layer, thereby precisely controlling the spectral power distribution to match desired color temperature and purity specifications
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
This configuration reduces drive voltage while maintaining good luminance and allows for adjustable emission wavelengths, enabling the production of white light with desired color properties for various applications, including use in display devices.
Implementation Method 1
an organic light-emitting diode (OLED) electroluminescent (EL) device having a light-emitting layer and a layer between the light-emitting layer and the cathode
Data Source
AI summary
An organic light emitting diode (OLED) device comprises a cathode, a light emitting layer and an anode, in that order, and, has located between the cathode and the light emitting layer, a layer containing (a) more than 10 vol% of a carbocyclic fused ring aromatic compound and (b) at least one salt or complex of an alkali or alkaline earth metal. The device provides reduced drive voltage and good luminance.