Light Emitting Device Electron Transporting Layers Luminance
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Solution Overview
Problem
The luminance of existing light emitting devices is not sufficient.
Innovation Solution
A light emitting device comprising an anode, a cathode, a phosphorescent light emitting layer, an electron transporting layer made of an organic compound, and specific metal materials, with certain compounds in the electron transporting layers and cathode, utilizing an iridium complex, and satisfying specific energy and electron affinity conditions to enhance luminance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional electron transporting layers are used in light emitting devices, then the device structure is simple, but the luminance is insufficient
Solution Approach 1:
The electron transporting layer is divided into two distinct layers: a first electron transporting layer adjacent to the light emitting layer, and a second electron transporting layer adjacent to the cathode. This segmentation allows each layer to be optimized for different functions, with the first layer focusing on electron transport from the light emitting layer and the second layer on electron injection from the cathode, thereby achieving high luminance while maintaining reasonable structural complexity
Solution Approach 2:
Different materials with specific properties are selected for each electron transporting layer based on their local functional requirements. The first electron transporting layer uses materials with appropriate LUMO levels to accept electrons from the light emitting layer, while the second layer uses materials optimized for electron injection from the cathode. This local optimization of material properties enables high luminance output
2Illumination intensity
If the electron transporting layers are optimized for high luminance, then the luminance increases, but the material selection and energy level matching become more complex
Solution Approach 1:
The invention establishes specific parameter ranges for energy levels (HOMO and LUMO values) that materials in the electron transporting layers must satisfy. The first electron transporting layer requires LUMO between -2.0 to -3.5 eV, while the second layer requires LUMO between -2.5 to -4.0 eV. These parameter specifications guide material selection and ensure proper energy level matching, achieving high luminance through systematic parameter control
Solution Approach 2:
The electron transporting layers are constructed using composite material systems that combine different organic compounds with complementary properties. This allows the device to achieve high luminance through synergistic material combinations while providing flexibility in selecting specific compounds that meet the energy level requirements
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 device achieves high luminance emission by optimizing the energy levels and materials in the electron transporting and cathode layers, improving the light emitting performance.
Implementation Method 1
a phosphorescent light emitting layer disposed between the anode and the cathode
Implementation Method 2
an electron transporting layer (B) disposed between the cathode and the light emitting layer and adjacent to the cathode, and an electron transporting layer (A) disposed between the light emitting layer and the electron transporting layer (B)
Data Source
AI summary
To provide a light emitting device capable of emitting light at high luminance. A light emitting device comprising an anode, a cathode, a phosphorescent light emitting layer, an electron transporting layer (B) disposed between the cathode and the light emitting layer and adjacent to the cathode, and an electron transporting layer (A) disposed between the light emitting layer and the electron transporting layer (B) , wherein P (eV) which is the smallest work function of the metal material contained in an amount of 1% by weight or more in the cathode, Q (eV) which is the smallest electron affinity of the compound contained in an amount of 5% by weight or more in the light emitting layer, RA (eV) which is the smallest electron affinity of the compound contained in an amount of 5% by weight or more in the electron transporting layer (A) and RB (eV) which is the smallest electron affinity of the compound contained in an amount of 5% by weight or more in the electron transporting layer (B) satisfy the formulae (1A) to (4A) : P>3.5 Q<2.7 P>RB>Q RB>RA