Layered Electron Transport Structure for Long-Life Light-Emitting Devices
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Solution Overview
Problem
Existing light-emitting devices face challenges in achieving long lifetime, high reliability, low driving voltage, and high emission efficiency.
Innovation Solution
A light-emitting device structure comprising a first electrode, a first light-emitting layer, a first layer containing an electron-transport material and a metal or metallic salt, a second layer with a lower concentration of the metal, and a second electrode, which includes an electron-injection material, is designed to control electron injection and suppress excess electrons, thereby improving device characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If a conventional organic EL device structure is used, then the device can be formed in a film form with planar light emission, but the device lifetime is insufficient
Solution Approach 1:
The electron transport layer is divided into multiple layers (first electron transport layer, second electron transport layer, third electron transport layer) with different metal concentrations. This segmentation allows each layer to perform specialized functions: the first layer provides high electron injection, the second layer controls electron concentration to prevent excess electrons, and the third layer maintains electron transport. This layered structure resolves the contradiction by improving device lifetime through controlled electron management while maintaining the film form structure for planar light emission.
Solution Approach 2:
Different regions of the electron transport layer are given different metal concentrations to create local quality variations. The first electron transport layer has a first metal concentration, the second layer has a second metal concentration (optimized to prevent excess electrons), and the third layer has a third metal concentration. This local quality approach allows the device to achieve long lifetime in specific regions while maintaining overall film form integrity and planar light emission characteristics.
2Speed
If the metal concentration in the electron transport layer is increased to improve electron injection, then electron injection is enhanced, but excess electrons are generated which reduces device lifetime
Solution Approach 1:
The metal concentration parameter is changed across different layers of the electron transport layer. The first electron transport layer has a first metal concentration optimized for electron injection, the second layer has a second metal concentration that prevents excess electron generation, and the third layer has a third metal concentration that maintains electron transport. This parameter change approach allows the device to achieve high electron injection speed while preventing excess electrons that would reduce lifetime, thereby resolving the technical contradiction.
3Device complexity
If a simple electron transport layer structure is used, then the device structure is simple, but the driving voltage is high and emission efficiency is low
Solution Approach 1:
The electron transport layer is segmented into three distinct layers with different metal concentrations and electron transport materials. This segmentation enables optimized electron injection and transport in each layer, resulting in reduced driving voltage and improved emission efficiency. Although the structure becomes more complex, the segmentation allows for precise control of electron behavior, resolving the contradiction between structural simplicity and electrical performance.
Solution Approach 2:
The electron transport layer uses composite materials with different metal concentrations and electron transport materials in each sub-layer. This composite approach allows optimization of electron injection and transport properties in each layer, achieving low driving voltage and high emission efficiency. The composite material strategy resolves the contradiction by balancing structural complexity with enhanced electrical performance.
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 structure enhances the device's lifetime, reliability, and emission efficiency by reducing driving voltage and increasing current efficiency, facilitating high-definition and large display device manufacturing with improved alignment accuracy.
Implementation Method 1
The first organic compound and the second organic compound are each an electron-transport material
Implementation Method 2
The second substance is an electron-injection material
Implementation Method 3
Research and development has been actively conducted on light-emitting devices using organic electroluminescence (EL) phenomenon
Data Source
AI summary
A light-emitting device with a long lifetime is provided. A light-emitting device with high reliability is provided. The light-emitting device includes a first electrode, a first light-emitting layer, a first layer, a second layer, a third layer, a second light-emitting layer, and a second electrode stacked in this order. The first layer contains a first organic compound and a first substance. The second layer contains a second organic compound. The third layer contains a second substance. The first organic compound is an electron-transport material. The first substance is a metallic salt, a metal oxide, or an organometallic salt. The second organic compound is an electron-transport material. The second substance is an electron-injection material. The second layer has a lower concentration of the first substance than the first layer.