Organic Electroluminescent Device with Graded Dye Distribution
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Solution Overview
Problem
Current organic electroluminescent devices face challenges with low luminescence efficiency, particularly with blue light-emitting materials using triplet-triplet annihilation, and high costs and environmental concerns with phosphorescent materials, while Thermally Activated Delayed Fluorescence (TADF) materials do not meet efficiency demands.
Innovation Solution
An organic electroluminescent device with a light-emitting layer comprising a host material, sensitizer, and dye, where the dye content is unevenly distributed across sections, with lower dye content in sections contacting the functional layers, enhancing exciton utilization and luminescence efficiency by reducing carrier capture and quenching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If blue light-emitting materials use triplet-triplet annihilation (TTA) to increase singlet excitons, then the total amount of singlet excitons increases, but the exciton utilization rate is limited to below 62.5%
Solution Approach 1:
The patent applies local quality by creating different dye content concentrations in different sections of the light-emitting layer. The first section (contacting first functional layer) and Nth section (contacting second functional layer) have lower dye content, while intermediate sections have higher dye content. This spatial variation in dye concentration optimizes exciton utilization in carrier-rich regions while maintaining high singlet exciton generation through TTA in intermediate regions.
2Loss of energy
If phosphorescent material is used for red and green light-emitting, then luminescence efficiency is improved, but cost increases and environmental friendliness decreases due to precious metals
Solution Approach 1:
The patent replaces expensive phosphorescent materials containing precious metals with organic fluorescent dye materials that are cheaper and environmentally friendly. By optimizing the spatial distribution of dye content and using sensitizers, the invention achieves high luminescence efficiency without relying on precious metal-based phosphorescent materials.
3Quantity of substance
If TADF material is used to utilize both singlet and triplet excitons, then exciton utilization probability increases, but luminescence efficiency still cannot meet device demands
Solution Approach 1:
The patent combines TADF materials with spatially varying dye content distribution. The lower dye content in sections contacting functional layers reduces carrier capture and quenching, while intermediate sections with higher dye content maintain high exciton utilization. This local optimization allows TADF materials to achieve device-level luminescence efficiency by addressing the quenching problem at carrier injection interfaces.
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
Significantly improves luminescence efficiency by increasing exciton utilization and reducing quenching phenomena, while also offering cost-effective and environmentally friendly alternatives to traditional materials.
Implementation Method 1
the blue light-emitting materials used in the organic electroluminescent device on the production line are mainly common triplet-triplet annihilation (TTA) material, which uses the annihilation effect of triplet excitons to increase a total amount of singlet excitons
Implementation Method 2
the organic electroluminescent device includes a cathode, an anode, and a functional layer (such as a light-emitting layer) located between the cathode and anode. When applying voltage, electrons from the cathode and holes from the anode will migrate towards the light-emitting layer and combine to produce excitons respectively, emitting light with different wavelengths
Implementation Method 3
Thermally Activated Delayed Fluorescence (TADF) material is widely applied to the luminescent material for organic electroluminescent device. The TADF material can simultaneously use the singlet exciton with a probability of 25% and the triplet exciton with a probability of 75%
Data Source
AI summary
An organic electroluminescent device and a display device. The organic electroluminescent device includes a first functional layer, a light-emitting layer, and a second functional layer that are sequentially stacked. The light-emitting layer includes a host material, a sensitizer, and a dye; the light-emitting layer includes N sections in a stacking direction, with a first section being in contact with the first functional layer and a Nth section being in contact with the second functional layer, N>1; where among the N sections, a section with the highest dye content is the highest critical section, where D1<Dmax and D1≤Dother, and/or DN<Dmax and DN≤Dother. The special composition of the light-emitting layer of the organic electroluminescent device can effectively reduce a probability that carriers are captured by the dye, thereby making the organic electroluminescent device have high luminescence efficiency by suppressing exciton quenching.