OLED Interlayer Energy Level Optimization for Hole Injection
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Solution Overview
Problem
Existing organic light-emitting devices face challenges in achieving low driving voltage, high efficiency, and long lifespan due to limitations in light-emission efficiency and hole injection processes.
Innovation Solution
The implementation of a light-emitting device structure with a specific interlayer configuration, including a hole transport region, first and second emission auxiliary layers, and an emission layer, where the energy levels of the compounds satisfy certain equations to minimize energy barriers and optimize hole injection and transport, thereby enhancing efficiency and lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional hole transport region structure is used, then device structure is simple, but light-emission efficiency is low and lifespan is short
Solution Approach 1:
The hole transport region is segmented into multiple functional layers: a hole transport layer adjacent to the emission layer, and a hole injection layer adjacent to the first electrode. This segmentation allows each layer to be optimized for its specific function, improving overall device reliability and lifespan while managing the complexity through modular design.
Solution Approach 2:
The hole transport layer acts as an intermediary between the hole injection layer and the emission layer, facilitating efficient hole transport while maintaining energy level compatibility. This intermediary structure resolves the contradiction by enabling improved lifespan through optimized hole injection and transport without requiring complete redesign of the entire device architecture.
2Productivity
If energy barrier is reduced for efficient hole injection, then light-emission efficiency improves, but driving voltage increases
Solution Approach 1:
The patent optimizes the energy levels of compounds in each layer to achieve balanced hole injection and transport. By carefully selecting materials with appropriate HOMO levels and adjusting layer thicknesses, the device achieves high light-emission efficiency while maintaining moderate driving voltage through parameter optimization rather than extreme energy barrier reduction.
Solution Approach 2:
Different regions of the hole transport region are assigned different material properties: the hole injection layer uses materials optimized for hole injection from the electrode, while the hole transport layer uses materials optimized for hole transport to the emission layer. This local quality differentiation allows efficient hole injection without requiring uniformly low energy barriers throughout the entire structure, thus managing driving voltage requirements.
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 light-emission efficiency and extended lifespan by ensuring efficient hole injection and transport, reducing the driving voltage and avoiding the need for p-dopants, which lowers manufacturing costs and prevents capacitance increases.
Implementation Method 1
Carriers, such as holes and electrons, recombine in the emission layer to produce excitons. These excitons transit from an excited state to a ground state, thereby generating light.
Data Source
AI summary
A light-emitting device includes: a first electrode; a second electrode opposing the first electrode; and an interlayer between the first electrode and the second electrode, wherein the interlayer includes an emission layer, a first emission auxiliary layer, a second emission auxiliary layer, and a hole transport region, the hole transport region is disposed between the first electrode and the emission layer, the first emission auxiliary layer and the second emission auxiliary layer are disposed between the emission layer and the hole transport region, the first emission auxiliary layer includes a first compound, the second emission auxiliary layer includes a second compound, the hole transport region includes a hole transport compound, and the first compound and the hole transport compound satisfy the Equation 1, as defined herein.