OLED Emissive Layer Composition for Efficiency and Drive Durability
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Solution Overview
Problem
The use of iridium complexes with sulfur-containing or nitrogen-containing structures in the light-emitting layer of organic light-emitting elements leads to issues with luminescence efficiency and drive durability.
Innovation Solution
An organic light-emitting element is designed with a light-emitting layer containing a dopant material represented by a specific general formula, a host material as an aromatic hydrocarbon compound, and an assist material with a lower LUMO level than the host, facilitating improved dispersibility and energy transfer through the use of a hydrocarbon compound as the host material and an iridium complex as the dopant.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If sulfur-containing or nitrogen-containing structures are used in the light-emitting layer, then luminescence efficiency is improved, but drive durability deteriorates
Solution Approach 1:
The patent introduces a host material as an intermediary between the iridium complex dopant and the sulfur/nitrogen-containing structures. The host material mediates the interaction, allowing energy transfer to occur while protecting the iridium complex from direct contact with potentially harmful sulfur or nitrogen atoms, thus maintaining luminescence efficiency while improving drive durability
Solution Approach 2:
The patent changes the chemical composition parameters of the light-emitting layer by specifying particular ratios of dopant material (iridium complex), host material, and assist material. By optimizing these compositional parameters and selecting specific molecular structures with appropriate HOMO-LUMO energy levels, the patent achieves both high luminescence efficiency and improved drive durability
2Use of energy by moving object
If phosphorescent organometallic complexes are used, then luminescence efficiency is improved, but dispersibility deteriorates
Solution Approach 1:
The patent creates a composite material system consisting of iridium complex dopant, host material, and assist material. This composite approach allows the iridium complex to maintain its phosphorescent properties for high luminescence efficiency while the host and assist materials provide a compatible matrix that ensures good dispersibility and prevents aggregation of the organometallic complex
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 enhances luminescence efficiency and drive durability by improving dispersibility and energy transfer, resulting in a more efficient and long-lasting organic light-emitting element.
Implementation Method 1
an assist material having a lower LUMO level than the host material... facilitates improved dispersibility and energy transfer
Implementation Method 2
Positive holes (holes) and electrons from the positive and negative electrodes recombine and form excitons in the organic compound layer. An organic light-emitting element emits light when the excitons return to their ground state.
Implementation Method 3
the use of phosphorescence has been proposed to improve the luminescence efficiency of organic EL elements
Data Source
AI summary
A organic light-emitting element including a positive electrode, a light-emitting layer, and a negative electrode in this order, wherein the light-emitting layer contains a dopant material, a host material, and an assist material, the dopant material is a compound represented by the following general formula [1], the host material is a hydrocarbon compound, and the assist material has a lower LUMO level than the host material. In the formula [1], R1 to R10 denote a hydrogen atom, an alkyl group, or the like. X denotes O or S. m denotes an integer in the range of 1 to 3, and n denotes an integer in the range of 0 to 2, provided that m+n is 3. The partial structure IrLn is any one of structures represented by the following formulae [2] and [3], wherein R11 to R21 denote a hydrogen atom, an alkyl group, or the like.