Light-Emitting Element Layer Structure for Voltage Stability
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Solution Overview
Problem
Conventional light-emitting elements experience an increase in driving voltage over time and resistance with film thickness, leading to inefficiencies and potential short circuits due to electrode unevenness.
Innovation Solution
A light-emitting element structure comprising a first layer generating holes, a second layer generating electrons, and a third layer with a light-emitting substance, where the second and third layers are in contact to inject electrons, and the thicknesses of the layers are adjusted to minimize voltage increase and resistance, allowing for efficient light emission and reduced spectral variation with angle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the film thickness is increased to improve light emission, then the light emission intensity is improved, but the resistance value increases
Solution Approach 1:
The patent divides the light-emitting element into multiple functional layers (first layer with hole transporting substance, second layer with light-emitting substance, third layer with electron transporting substance) between the electrodes. This segmentation allows each layer to have optimized thickness and material properties, enabling sufficient light emission while maintaining low resistance through efficient charge carrier transport in each specialized layer.
2Duration of action of moving object
If the light-emission time is extended to improve display duration, then the display duration is improved, but the driving voltage increases
Solution Approach 1:
The patent changes the material parameters by selecting specific substances with complementary properties: the first layer uses a hole transporting substance, the second layer uses a light-emitting substance, and the third layer uses an electron transporting substance. This parameter optimization enables sustained light emission over extended periods while maintaining stable driving voltage through efficient recombination of electrons and holes in each layer.
3Reliability
If the electrode distance is increased to prevent short circuits, then the reliability is improved, but the light extraction efficiency decreases
Solution Approach 1:
The patent applies local quality by creating distinct functional zones within the light-emitting element. The first and third layers are positioned closer to their respective electrodes to facilitate charge injection and transport, while the second layer (light-emitting layer) is positioned in the middle to optimize light emission. This localized functional distribution maintains electrode separation for reliability while ensuring efficient light extraction from the central emission zone.
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 solution results in a reliable light-emitting element with stable driving voltage, reduced resistance, and improved light extraction efficiency, preventing short circuits and maintaining consistent emission spectra across different viewing angles.
Implementation Method 1
The first layer is a layer generating holes
Implementation Method 2
The second layer is a layer generating electrons
Implementation Method 3
The second layer and the third layer are in contact with each other so as to inject electrons generated in the second layer into the third layer
Implementation Method 4
Such a light-emitting element emits light when an excited electron, which is formed by a recombination of an electron injected from one electrode and a hole injected from the other electrode, returns to a ground state
Data Source
AI summary
The present invention provides a light-emitting element having less increase in driving voltage with the accumulation of light-emission time, and provides a light-emitting element having less increase in resistance value with the increase in film thickness. A light-emitting element includes a first layer, a second layer and a third layer between a first electrode and a second electrode. The first layer is provided to be closer to the first electrode than the second layer, and the third layer is provided to be closer to the second electrode than the second layer. The first layer is a layer including an aromatic amine compound and a substance showing an electron accepting property to the aromatic amine compound. The second layer includes a substance of which an electron transporting property is stronger than a hole transporting property, and a substance showing an electron donating property to the aforementioned substance.