Multi-Layer Light-Emitting Element with Charge-Generation Layers
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Solution Overview
Problem
Conventional light-emitting elements with a single light-emitting layer face challenges in achieving high luminance while maintaining low power consumption and long lifetime, as they require high current density, which increases power consumption and accelerates deterioration.
Innovation Solution
A light-emitting element with multiple EL layers, including an electron-injection buffer layer, electron-relay layer, and charge-generation layer, is designed to facilitate efficient carrier transport and reduce driving voltage, comprising specific materials like alkali metals, perylene derivatives, and transition metal oxides to enhance electron and hole transport.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a large amount of current is applied to increase luminance, then the luminance of the EL element increases, but power consumption increases and deterioration accelerates
Solution Approach 1:
The light-emitting element is divided into multiple EL layers (first EL layer, second EL layer, etc.) stacked in series. Each EL layer has its own light-emitting material and emits light independently when carriers recombine. This segmentation allows the total luminance to be the sum of light from multiple layers, achieving high luminance without requiring excessively high current density in a single layer, thus reducing power consumption and deterioration acceleration.
2Illumination intensity
If a large amount of current is applied to increase luminance, then the luminance of the EL element increases, but the lifetime of the EL element decreases
Solution Approach 1:
The light-emitting element is divided into multiple EL layers (first EL layer, second EL layer, etc.) stacked in series. Each EL layer has its own light-emitting material and emits light independently when carriers recombine. This segmentation allows the total luminance to be the sum of light from multiple layers, achieving high luminance without requiring excessively high current density in a single layer, thus reducing power consumption and deterioration acceleration.
3Illumination intensity
If multiple EL layers are stacked to increase luminance, then the luminance increases, but the device complexity increases
Solution Approach 1:
Multiple EL layers are stacked in series with charge-generation layers positioned between adjacent EL layers. The charge-generation layers serve dual purposes: generating carriers (electrons and holes) that are injected into the EL layers and facilitating carrier transport between layers. This merging of functions reduces the need for separate complex injection and transport layers, simplifying the overall device structure while maintaining high luminance output.
4Productivity
If charge-generation layers are added between EL layers to facilitate carrier transport, then carrier transport efficiency improves, but device complexity increases
Solution Approach 1:
Multiple EL layers are stacked in series with charge-generation layers positioned between adjacent EL layers. The charge-generation layers serve dual purposes: generating carriers (electrons and holes) that are injected into the EL layers and facilitating carrier transport between layers. This merging of functions reduces the need for separate complex injection and transport layers, simplifying the overall device structure while maintaining high luminance output.
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 multi-layer structure enables high luminance emission with improved lifetime and reduced power consumption, achieving low-voltage driving and extended operational life.
Implementation Method 1
a first layer including a first donor material and being in contact with the m-th EL layer, a second layer including an electron-transport material and a second donor material and being in contact with the first layer, and a third layer including a hole-transport material and an acceptor material and being in contact with the second layer and with the (m+1)-th EL layer
Implementation Method 2
When current flows in the light-emitting layer, the light-emitting material is excited, and then the EL element can emit light of a predetermined color
Data Source
AI summary
An object is to provide a light-emitting element capable of emitting light with a high luminance even at a low voltage, and having a long lifetime. The light-emitting element includes n EL layers between an anode and a cathode (n is a natural number of two or more), and also includes, between m-th EL layer from the anode and (m+1)-th EL layer (m is a natural number, 1≤m≤n−1), a first layer including a first donor material in contact with the m-th EL layer, a second layer including an electron-transport material and a second donor material in contact with the first layer, and a third layer including a hole-transport material and an acceptor material in contact with the second layer and the (m+1)-th EL layer.