Organic Light-Emitting Element with Energy Level Alignment
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Solution Overview
Problem
The existing white organic light-emitting elements face issues with increased drive voltage and reduced durability due to hole accumulation at the interface between the blue-light-emitting layer with electron-trapping properties and the hole blocking layer, leading to poor light emission balance.
Innovation Solution
An organic light-emitting element configuration where the energy levels of the light-emitting layer, functional layer, and electron transport layer satisfy specific relations, ensuring low drive voltage and durability by using a first light-emitting layer with a host and dopant material combination that traps electrons and allows hole transport without accumulation, and optionally incorporating a second light-emitting layer for enhanced color emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a hole blocking layer is provided on the light-emitting-layer side of the electron transport layer, then light emission balance is improved, but drive voltage increases and durability decreases due to hole accumulation at the interface
Solution Approach 1:
A functional layer is introduced as an intermediary between the first light-emitting layer and the hole blocking layer. This functional layer has electron-trapping properties that prevent hole accumulation at the interface, while still allowing the hole blocking layer to function effectively. The functional layer acts as a mediator that resolves the contradiction between maintaining light emission balance and preventing hole accumulation.
Solution Approach 2:
The invention changes the energy level parameters of the functional layer to satisfy specific relationships with the light-emitting layer and hole blocking layer. By carefully selecting the HOMO and LUMO energy levels of the functional layer material, the system achieves both effective hole blocking and prevention of hole accumulation, resolving the contradiction between light emission balance and durability.
2Illumination intensity
If a dual-color light-emitting layer with electron-trapping properties is used, then light emission balance is improved, but drive voltage increases due to electron trapping
Solution Approach 1:
The invention segments the light-emitting function into separate first and second light-emitting layers with different dopant materials. The first light-emitting layer uses a dopant with deep LUMO level for electron trapping, while the second light-emitting layer uses a dopant with shallow LUMO level. This segmentation allows each layer to perform its specific function optimally without excessive electron trapping that would increase drive voltage.
Solution Approach 2:
Different regions of the light-emitting structure have different electron-trapping characteristics. The first light-emitting layer has strong electron-trapping properties for achieving good light emission balance, while the second light-emitting layer has weaker electron-trapping properties to maintain lower drive voltage. This local differentiation of properties resolves the contradiction between light emission balance and drive voltage.
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
The solution achieves a low drive voltage and improved durability of the organic light-emitting element, maintaining light emission balance and extending the element's lifespan by preventing hole accumulation and optimizing energy level interactions.
Implementation Method 1
a first light-emitting layer containing a first host material and a first dopant material, wherein the first dopant material has electron-trapping properties
Implementation Method 2
when the first host material has a LUMO energy level LUMOh1, the first dopant material has a LUMO energy level LUMOd1, the first host material has a HOMO energy level HOMOh1, the first dopant material has a HOMO energy level HOMOd1, and an organic material that forms the functional layer has a HOMO energy level HOMOFL, formulae [1] to [3] are satisfied
Implementation Method 3
the organic material that forms the functional layer has a HOMO energy level HOMOFL>HOMOh1
Implementation Method 4
a hole blocking layer provided on the light-emitting-layer side of the electron transport layer
Implementation Method 5
organic light-emitting element which is one of light-emitting elements
Data Source
AI summary
The present disclosure provides an organic element including an anode, a first layer, a functional layer in contact with the first layer, and a cathode in this order. Energy levels of a first host material and a first dopant material that form the first layer and an organic material that forms the functional layer satisfy specific relations.