OLED Hole-Blocking Layer Thickness Optimization for Emission Efficiency
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Solution Overview
Problem
Conventional organic EL display devices face challenges in optimizing emission intensity and color purity due to limitations in the structure and thickness of the hole-blocking and electron-transporting layers, which affect the efficiency and reliability of light-emitting elements.
Innovation Solution
The display device incorporates a specific structure for each light-emitting element with varying thicknesses of hole-blocking and electron-transporting layers, where the hole-blocking layers have higher electron mobility than the electron-transporting layers, allowing for optical adjustment and improved emission efficiency without increasing driving voltage, and the use of high electron mobility materials in the hole-blocking layers ensures efficient electron transport and emission region shifting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the thickness of hole-blocking and electron-transporting layers is increased to improve emission intensity, then emission efficiency is improved, but driving voltage increases and power consumption increases
Solution Approach 1:
The patent applies parameter changes by systematically varying the thickness of hole-blocking and electron-transporting layers to optimize emission efficiency. By adjusting layer thickness parameters within specific ranges, the patent achieves improved emission intensity without excessive voltage increase, resolving the contradiction between productivity and energy consumption.
Solution Approach 2:
The patent implements local quality by creating different layer thickness configurations for different functional layers. The hole-blocking layer and electron-transporting layer have different thickness values optimized for their specific functions, allowing each layer to contribute optimally to emission efficiency while controlling overall power consumption.
2Manufacturing precision
If the thickness of hole-blocking and electron-transporting layers is adjusted to optimize emission color, then color purity is improved, but device complexity increases
Solution Approach 1:
The patent uses parameter changes to achieve color purity optimization by adjusting the thickness of functional layers. By controlling thickness parameters within specific ranges, the patent achieves narrow emission spectra and high color purity without requiring complex additional structures, thus managing device complexity.
Solution Approach 2:
The patent applies dynamics by making the layer thickness a variable parameter that can be adjusted to achieve different emission colors. This dynamic approach allows optimization of color purity for different wavelength regions (blue, green, red) by selecting appropriate thickness values, rather than requiring fixed complex structures for each color.
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 emission efficiency, particularly for elements with shorter wavelengths, achieves excellent color purity, and reduces power consumption while maintaining low driving voltage, resulting in a display device with improved reliability and color reproducibility.
Implementation Method 1
hole-blocking layers have higher electron mobility than the electron-transporting layers
Implementation Method 2
each light-emitting element possesses an electroluminescence layer (hereinafter, referred to as an EL layer) including an organic compound between a pair of electrodes
Implementation Method 3
the use of light-interference effect in or outside a light-emitting element increases emission intensity in a front direction and narrows an emission spectrum
Data Source
AI summary
Provided is a display device having first to third light-emitting elements. The first to third light-emitting elements each include: a first electrode; a hole-transporting layer over the first electrode; an emission layer over the hole-transporting layer; a hole-blocking layer over and in contact with the emission layer; an electron-transporting layer over and in contact with the hole-blocking layer; and a second electrode over the electron-transporting layer. An emission wavelength of the second light-emitting element is longer than that of the first light-emitting element and shorter than that of the third light-emitting element. A total thickness of the hole-blocking layer and the electron-transporting layer in the second light-emitting element is larger than that in the first light-emitting element and smaller than that in the third light-emitting element. A thickness of the hole-blocking layer is larger than that of the electron-transporting layer in each of the first to third light-emitting elements.