Organic Light-Emitting Element Host-Guest Emission Layer
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Solution Overview
Problem
Current organic light-emitting elements face challenges in achieving high light-emitting efficiency and long element lifetime, particularly due to the sublimability and heat stability issues of iridium complexes used in phosphorescent light-emitting elements.
Innovation Solution
An organic light-emitting element is designed with an emission layer comprising a heterocycle-containing compound as the host and an iridium complex represented by a specific general formula, where the iridium complex has three different ligands, reducing crystallinity and enhancing sublimability and heat stability, and the host is used in concentrations of 50 wt % or more to optimize carrier transport and exciton energy levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If an iridium complex with three different bidentate ligands is used as a guest material in a phosphorescent light-emitting element, then high phosphorescence quantum yield is achieved, but sublimability and heat stability deteriorate
Solution Approach 1:
The patent changes the chemical structure parameters of the iridium complex by introducing specific ligand types (formula L1 with C^N coordination mode) and controlling the number of carbon atoms in substituent groups (1-4 carbon atoms). These parameter modifications optimize the balance between phosphorescence quantum yield and heat stability, allowing the complex to maintain high luminescence efficiency while improving thermal resistance and sublimability.
Solution Approach 2:
The patent creates a composite emission layer system combining the iridium complex (guest) with a heterocycle-containing compound (host). This composite structure allows the host material to provide thermal stability and structural support while the iridium complex contributes high phosphorescence quantum yield. The host-guest interaction enables the system to achieve both high luminescence efficiency and improved heat stability simultaneously.
2Ease of operation
If the host content in the emission layer is increased to optimize carrier transport, then carrier balance improves, but the complexity of material composition increases
Solution Approach 1:
The patent optimizes the host content parameter to 5-50 wt% in the emission layer, establishing a quantitative range that balances carrier transport efficiency with material composition simplicity. This parameter optimization ensures sufficient host material to facilitate carrier transport and maintain carrier balance, while avoiding excessive complexity in the emission layer composition. The specific concentration range provides a practical guideline for device fabrication.
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 results in high light-emitting efficiency and extended element lifetime by improving sublimability and heat stability of the iridium complex, while the heterocycle-containing host reduces the energy gap, leading to reduced driving voltage and enhanced carrier balance in the emission layer.
Implementation Method 1
a phosphorescent light-emitting element is an organic light-emitting element that: includes, in its organic compound layer, a material that emits phosphorescence; and provides light emission derived from a triplet exciton of the material that emits phosphorescence
Implementation Method 2
the heterocycle-containing host reduces the energy gap, leading to reduced driving voltage and enhanced carrier balance in the emission layer
Data Source
AI summary
Provided is an organic light-emitting element having high light-emitting efficiency and a long element lifetime. Specifically, provided is an organic light-emitting element, including: an anode; a cathode; and an organic compound layer placed between the anode and the cathode, in which: the organic compound layer includes an emission layer; the emission layer includes at least a host and a guest; the guest is an iridium complex of a specific structure; the host is a heterocycle-containing compound; and a content of the host is 50 wt % or more with reference to a total amount of constituent materials for the emission layer.