OLED Emission Layer Host Layout for Longer Phosphorescent Lifetime
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Phosphorescent organic light emitting display devices with two types of host materials and one dopant suffer from reduced lifetime due to interface degradation and exciton-polaron interactions caused by high electron densities in the light emission area, leading to accelerated degradation.
Innovation Solution
The organic light emitting display device incorporates a second light emitting layer with a hole-type host and a first electron-type host, and a third light emitting layer with a first and second electron-type host, where the LUMO levels of the hosts are within specific ranges and have a small difference, and the electron mobility of the first host is lower than the second host to improve electron injection and stability, thereby reducing degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If phosphorescent devices use two types of host and one type of dopant to improve efficiency, then light emitting efficiency is improved, but lifetime is reduced due to interface degradation and exciton-polaron interaction
Solution Approach 1:
The light emitting layer is divided into multiple sub-layers (first light emitting sub-layer, second light emitting sub-layer, third light emitting sub-layer) with different host material compositions. This segmentation allows each sub-layer to have optimized electron mobility characteristics, preventing excessive electron accumulation at interfaces while maintaining overall high efficiency through the phosphorescent dopant distributed across all layers.
Solution Approach 2:
Different regions of the light emitting layer are assigned different host materials with specific electron mobility characteristics. The first light emitting sub-layer uses host materials with lower electron mobility to prevent electron accumulation, while subsequent layers use host materials with progressively higher electron mobility to facilitate electron transport away from the hole transport layer interface, thereby locally optimizing both efficiency and lifetime.
2Productivity
If high electron density is present in the light emission area, then electron-hole recombination efficiency is improved, but interface degradation accelerates and lifetime reduces
Solution Approach 1:
The electron mobility parameter of host materials is systematically varied across different light emitting sub-layers. By changing the electron mobility parameter from lower values in the first sub-layer to higher values in subsequent layers, the invention optimizes electron distribution to maintain high recombination efficiency while preventing excessive electron accumulation that causes interface degradation.
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 the lifetime of the organic light emitting display device by adjusting electron injection and mobility, leading to improved stability and reduced degradation of the light emitting layers.
Implementation Method 1
when a charge is injected into an organic light emitting layer formed between an anode and a cathode, emit light as electron-hole pairs are produced and dissipated
Implementation Method 2
phosphorescent devices using two types of host and one type of dopant are becoming a mainstream through improvements to the light emitting layer
Data Source
AI summary
An organic light emitting display device is disclosed. The organic light emitting display device includes a first light emitting part between an anode and a cathode, the first light emitting part having a first light emitting layer, and a second light emitting part between the first light emitting part and the cathode, the second light emitting part having a second light emitting layer and a third light emitting layer, wherein the second light emitting layer includes a hole-type host and a first electron-type host, and the third light emitting layer includes a first electron-type host and a second electron-type host.