Organic Electroluminescent Device Host Material Energy Level Optimization
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Solution Overview
Problem
Existing organic electroluminescent devices face challenges in achieving enhanced efficiency and low driving voltage due to limitations in hole injection properties and material stability, particularly in the light emitting layer and electron transfer processes.
Innovation Solution
The organic electroluminescent device incorporates a light emitting layer with a first host material having a HOMO energy level of −5.9 eV or lower and a second host material with a HOMO energy level 0.1 eV to 0.2 eV higher, along with an electron transfer layer comprising specific compounds represented by Chemical Formulae 1 or 2, to improve hole injection and electron transfer efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a conventional organic material layer structure is used, then the device structure is simple, but the current efficiency is low and driving voltage is high
Solution Approach 1:
The organic material layer is segmented into multiple functional sub-layers: hole injection layer, hole transport layer, light emitting layer, electron transport layer, and electron injection layer. Each layer is optimized for its specific function, allowing improved current efficiency through targeted material selection and energy level matching at each interface.
Solution Approach 2:
Different regions of the device have specialized material compositions tailored to local requirements. The hole transport layer uses materials with specific HOMO levels optimized for hole injection, while the electron transport layer uses materials with specific LUMO levels optimized for electron injection and transport, creating locally optimized conditions throughout the device.
2Reliability
If materials with insufficient energy level matching are used, then the device structure is simple, but hole injection properties are poor
Solution Approach 1:
The invention systematically adjusts the HOMO energy levels of materials in the hole transport layer to achieve optimal energy level matching with adjacent layers. By selecting materials with specific HOMO levels, the device achieves improved hole injection efficiency without requiring complex structural modifications.
3Productivity
If conventional electron transfer layer materials are used, then the device structure is simple, but electron transfer efficiency is low
Solution Approach 1:
The electron transfer layer uses materials with specifically selected LUMO energy levels to optimize electron transfer efficiency. By adjusting the LUMO parameter of the electron transfer layer materials, the invention achieves better electron injection and transport performance while maintaining a manageable device structure.
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 enhances current efficiency and reduces driving voltage while improving the device's lifetime by optimizing the energy levels and material interactions within the light emitting and electron transfer layers.
Implementation Method 1
An organic light emission phenomenon generally refers to a phenomenon converting electrical energy to light energy using an organic material
Implementation Method 2
When a voltage is applied between the two electrodes in such an organic electroluminescent device structure, holes and electrons are injected to the organic material layer from the anode and the cathode, respectively
Implementation Method 3
when the injected holes and electrons meet, excitons are formed, and light emits when these excitons fall back to the ground state
Data Source
AI summary
The present specification relates to an organic electroluminescent device comprising: a first electrode; a second electrode; and an organic material layer provided between the first electrode and the second electrode, wherein the organic material layer comprises a light emitting layer and an electron transfer layer, the light emitting layer comprises a first host material, a second host material and a dopant material, the first host material has a HOMO energy level of −5.9 eV or lower, and the second host material has a HOMO energy level higher than a HOMO energy level of the first host material by 0.1 eV to 0.2 eV.