Light-emitting Element Stacked-layer Structure for Luminance Stability
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Solution Overview
Problem
Conventional light-emitting elements face challenges in maintaining reliable performance over long-time driving due to changes in carrier balance and emission color shifts, leading to reduced luminance and color purity, especially in high-definition displays requiring low power consumption and high emission efficiency.
Innovation Solution
A light-emitting element with a stacked-layer structure comprising a first, second, and third light-emitting layer, where the second layer emits light of the same color as the first and third layers, which have longer wavelengths, ensuring stable emission even with carrier balance changes, and utilizing phosphorescent materials for high efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional single-layer EL structure is used, then the device structure is simple, but luminance degradation occurs due to carrier balance changes during long-time driving
Solution Approach 1:
The EL layer is divided into three distinct light-emitting layers (first, second, and third light-emitting layers) with different emission characteristics. This segmentation allows each layer to contribute differently to the overall emission, with the first and third layers providing complementary emission to compensate for carrier balance shifts during operation, thereby maintaining luminance stability without excessive complexity.
Solution Approach 2:
The patent employs light-emitting materials with different emission wavelengths and characteristics in each layer. The first light-emitting layer uses a material with a first emission wavelength, the second layer uses a material with a second emission wavelength, and the third layer uses a material with a third emission wavelength. By carefully selecting these parameters, the patent achieves compensation for carrier balance changes while maintaining reasonable device complexity.
2Use of energy by moving object
If phosphorescent materials are used to improve emission efficiency, then power consumption is reduced, but color purity may be compromised
Solution Approach 1:
Different light-emitting materials with specific emission characteristics are assigned to different layers. The first and third light-emitting layers use materials with emission wavelengths that complement the second layer, creating localized emission zones with specific color characteristics. This allows the patent to maintain high color purity while utilizing phosphorescent materials for efficient energy conversion and low power consumption.
3Productivity
If the EL layer is shared among all subpixels to reduce material loss and manufacturing cost, then productivity increases, but achieving high color purity and high-definition display becomes more difficult
Solution Approach 1:
The EL layer structure is designed to serve multiple functions simultaneously. The stacked three-layer configuration enables the common EL layer to provide both high color purity through selective wavelength emission and high-definition display capability through precise color control. This multi-functionality allows the patent to achieve high productivity through shared EL layers while maintaining the precision required for high-definition displays.
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 maintains favorable characteristics throughout long-time driving, enhances color purity, and achieves high emission efficiency while reducing luminance degradation, suitable for high-definition displays with low power consumption.
Implementation Method 1
utilizing phosphorescent materials for high efficiency
Implementation Method 2
a micro optical resonator (microcavity) structure utilizing a resonant effect of light between a pair of electrodes is used to increase the intensity of light having a specific wavelength
Data Source
AI summary
A highly reliable light-emitting element which can keep favorable characteristics throughout long-time driving is provided. In addition, a light-emitting element with high color purity and high emission efficiency is provided. Furthermore, a light-emitting device having a long lifetime in which the light-emitting element is used is provided. Moreover, an electronic device and a lighting device each of which has a long lifetime are provided. In the light-emitting element including an EL layer between a pair of electrodes, the EL layer has a stacked-layer structure of a first light-emitting layer, a second light-emitting layer, and a third light-emitting layer. The light-emitting layer includes an electron-transport material, a hole-transport material, and a light-emitting material. Furthermore, light emitted from the first light-emitting layer and light emitted from the third light-emitting layer have the same color and each have a longer wavelength than light emitted from the second light-emitting layer.