OLED Double Emission Layers and Hole Blocking
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Solution Overview
Problem
Existing organic light-emitting devices (OLEDs) face challenges in achieving high efficiency and long lifespan due to issues with exciton formation and electron migration.
Innovation Solution
The implementation of a novel stack structure in OLEDs, featuring a first emission layer and a second emission layer with different hosts and light-emitting materials, along with a hole blocking layer, to enhance exciton formation and prevent hole migration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single emission layer is used in OLEDs, then the device structure is simple, but the photoluminescence efficiency is insufficient and exciton formation is limited
Solution Approach 1:
The emission layer is divided into multiple emission layers (first emission layer and second emission layer) with different hosts and light-emitting materials. Each emission layer generates excitons independently, increasing the total number of excitons formed and improving photoluminescence efficiency while maintaining reasonable structural complexity
Solution Approach 2:
The patent introduces a vertical stacking dimension by arranging multiple emission layers at different positions between the electrodes. This multi-layer vertical structure allows exciton generation at multiple levels, enhancing overall light emission efficiency without significantly complicating the manufacturing process
2Use of energy by moving object
If electron transport region is present, then electron transport is enabled, but hole migration to the electron transport region causes energy loss and reduced device lifespan
Solution Approach 1:
A hole blocking layer is introduced as an intermediary component between the emission layer and the electron transport region. This layer selectively blocks hole migration toward the electron transport region while maintaining electron transport functionality, thereby preventing energy loss and improving device lifespan
3Productivity
If multiple emission layers with different hosts are used, then exciton formation is enhanced, but the device structure becomes more complex
Solution Approach 1:
The emission region is segmented into multiple emission layers, each containing different host materials and light-emitting materials optimized for specific exciton generation purposes. This segmentation enables enhanced exciton formation through multiple independent emission pathways
Solution Approach 2:
Each emission layer is designed with specific local quality characteristics - different host materials and light-emitting materials are selected for each layer to optimize exciton formation at that particular location. The first emission layer and second emission layer have distinct material compositions tailored to their specific functions
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 increases photoluminescence efficiency, reduces electron loss, and improves the lifespan of OLEDs by concentrating excitons at the interface between the emission layers and preventing hole migration to the electron transport region.
Implementation Method 1
The excitons may transit (e.g., transition or relax) from an excited state to a ground state, thus generating light
Data Source
AI summary
An organic light-emitting device includes: a first electrode; a second electrode facing the first electrode; an emission region between the first electrode and the second electrode and including a first emission layer and a second emission layer; and a hole blocking layer between the first emission layer and the first electrode, or between the second emission layer and the second electrode, wherein the second emission layer may be between the first emission layer and the hole blocking layer, the first emission layer may include a first host and a first light-emitting material, the second emission layer may include a second host and a second light-emitting material, and the first light-emitting material and the second light-emitting material may respectively be included in the first emission layer and the second emission layer at an identical ratio.