Organic Electroluminescent Device Host Material Energy Level Tuning
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Solution Overview
Problem
Conventional organic electroluminescent devices with a single-layered structure suffer from short service life due to exciton quenching, which affects luminous efficiency and device longevity.
Innovation Solution
An organic electroluminescent device configuration utilizing a single-layered light emitting layer composed of a host material and a dye, where the host material has a small difference between its singlet and triplet state energy levels, allowing for efficient electron and hole injection and reducing exciton quenching, thereby increasing luminous efficiency and extending service life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-layered light emitting layer is used to simplify device structure, then device complexity is reduced, but exciton quenching occurs at the electrode interface causing short service life
Solution Approach 1:
An electron transport layer is introduced as an intermediary between the light emitting layer and the electrode. This layer acts as a buffer to prevent direct contact between excitons and the metal electrode, thereby eliminating exciton quenching while maintaining the simplicity of the single-layered light emitting layer structure.
2Ease of manufacture
If conventional organic materials are used in single-layered structure, then manufacturing is simplified, but carrier injection imbalance causes light emitting area to shift, reducing efficiency
Solution Approach 1:
The electron transport layer is designed with specific energy level parameters that match both the light emitting layer and the electrode. By carefully selecting materials with appropriate HOMO and LUMO levels, the patent achieves balanced carrier injection and prevents light emitting area shift, thereby maintaining high luminous efficiency.
3Device complexity
If triplet state energy is not utilized efficiently, then device structure remains simple, but luminous efficiency is limited
Solution Approach 1:
The electron transport layer continuously transports electrons while the host material continuously converts triplet excitons to singlet excitons through TADF mechanism. This continuous conversion and transport process ensures efficient utilization of triplet state energy, achieving high luminous efficiency without complicating the device structure.
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 luminous efficiency and prolongs the service life of the device by effectively utilizing triplet state energy, simplifying the device structure and reducing production costs.
Implementation Method 1
The host material has a small difference between its singlet and triplet state energy levels, allowing for efficient electron and hole injection and reducing exciton quenching, thereby increasing luminous efficiency and extending service life
Implementation Method 2
The dye is made of a fluorescence material and/or a phosphorescence material
Implementation Method 3
The dye is made of a fluorescence material and/or a phosphorescence material
Implementation Method 4
The dye is made of a fluorescence material and/or a phosphorescence material
Data Source
Figure 1
AI summary
Disclosed is an organic electroluminescent device, comprising a substrate and light emitting units formed in sequence on the substrate, characterized in that, each of the light emitting units comprises a first electrode layer (1), a light emitting layer (2) and a second electrode layer (3), the light emitting layer comprises a host material and a dye, the host material is made of materials having both electron transport capability and hole transport capability; at least one material in the host material has a CT excited triplet state energy level T1 greater than its n-π excited triplet state energy level S1, and T1-S1 ≤ 0.3eV; or, at least one material in the host material has a CT excited triplet state energy level T1 greater than its n-π excited triplet state energy level S1, and T1-S1 ≥ 1eV, with the difference between its n-π excited second triplet state energy level and its CT excited first singlet state energy level being in the range of -0.1eV to 0.1eV. The organic electroluminescent device configuration can sufficiently utilize the triplet state energy in the host material and the dye to increase the luminous efficiency and prolong the service life of the device.