Light-Emitting Device with Layered Hole Transport and Light Extraction
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Solution Overview
Problem
Existing light-emitting devices face challenges in achieving low driving voltage, high luminescence efficiency, and long lifespan while maintaining high contrast ratios and short response times.
Innovation Solution
The light-emitting device incorporates a specific structure with a first electrode, a second electrode, an interlayer containing a hole transport region with multiple layers, and a capping layer, where the hole transport region includes a first layer with a p-dopant and a second layer with a specific amine-containing compound, and the capping layer has a refractive index optimized for different wavelengths, enhancing light extraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional single-layer hole transport region is used, then the device structure is simple, but the luminescence efficiency is insufficient
Solution Approach 1:
The hole transport region is divided into multiple layers: a first hole transport layer adjacent to the first electrode and a second hole transport layer adjacent to the emission layer. This segmentation allows each layer to be optimized for specific functions, improving overall luminescence efficiency while maintaining manageable structural complexity.
Solution Approach 2:
The patent employs composite material strategies by selecting specific materials for each hole transport layer with complementary properties. The first hole transport layer uses materials optimized for hole injection from the electrode, while the second layer uses materials optimized for hole transport to the emission layer, creating a composite structure that enhances overall efficiency.
2Ease of manufacture
If the triplet energy difference between p-dopant and hole transport material is small, then the material selection is easier, but the luminescence efficiency decreases
Solution Approach 1:
The patent specifies that the absolute difference between triplet energy of the p-dopant and triplet energy of the second hole transport material should be about 1.50 eV or greater. This parameter constraint ensures efficient energy transfer from the p-dopant to the hole transport material, significantly improving luminescence efficiency while providing clear material selection criteria.
3Device complexity
If a conventional capping layer with standard refractive index is used, then the manufacturing process is simple, but the light extraction efficiency is limited
Solution Approach 1:
The patent specifies that the capping layer should have a refractive index of about 1.70 or greater (for red light at 633 nm), about 1.90 or greater (for green light at 530 nm), or about 2.10 or greater (for blue light at 450 nm). This parameter optimization enhances light extraction efficiency by reducing total internal reflection at the device interface, while the capping layer can be integrated into existing manufacturing processes.
4Loss of energy
If high luminescence efficiency is achieved through optimized materials, then the driving voltage increases, but the device lifespan decreases
Solution Approach 1:
The patent applies local quality optimization by selecting specific materials for each layer based on their local functional requirements. The first hole transport layer uses materials optimized for hole injection, the second layer for hole transport, and the capping layer for light extraction. This localized optimization achieves high luminescence efficiency while distributing stress and heat generation, thereby extending device lifespan.
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 results in improved internal and external luminescence efficiency, lower driving voltage, and extended device lifespan, while maintaining high luminance and response speed.
Implementation Method 1
a difference between triplet energy of the p-dopant and triplet energy of the second hole transport material (e.g., an absolute value of the difference) may be about 1.50 eV or greater
Implementation Method 2
the first capping material may satisfy at least one selected from among Conditions 1 to 3: Condition 1 the first capping material has a refractive index of about 1.70 or greater for light having a wavelength of about 633 nm
Implementation Method 3
Carriers, such as holes and electrons, recombine in the emission layer to produce excitons. These excitons transit (relax) from an excited state to a ground state to thereby generate light
Data Source
AI summary
An electronic apparatus and electronic equipment each include a light-emitting device. The light-emitting device includes a first electrode, a second electrode opposite the first electrode, an interlayer arranged between the first electrode and the second electrode, and a capping layer, wherein the interlayer may include a hole transport region and an emission layer, the hole transport region may be arranged between the first electrode and the emission layer, the hole transport region may include a first layer and a second layer, the first layer may be arranged between the first electrode and the second layer, the first layer may include a first hole transport material and a p-dopant, the second layer may include a second hole transport material.