Organic EL Emitting Layer with TADF Host for High-Current Efficiency
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing fluorescent organic electroluminescence devices face efficiency limitations in high current density areas, despite advancements in technologies like TTF and TADF mechanisms, necessitating improvements in luminous efficiency.
Innovation Solution
Incorporating a specific compound as a host material and a fluorescent dopant material in the emitting layer, characterized by a formula (1), to enhance light emission efficiency in practical high-current-density areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If TTF mechanism is used to generate delayed fluorescence, then internal quantum efficiency can be raised up to 40%, but luminous efficiency decreases in high current density areas
Solution Approach 1:
The patent changes the energy level parameters of the host material by selecting compounds with specific ΔST values (0.0-0.3 eV) to enable TADF mechanism. This parameter change allows efficient triplet-to-singlet conversion at low current densities while maintaining stability at high current densities, resolving the efficiency roll-off problem
Solution Approach 2:
The patent uses composite material systems combining specific host materials (formulas 1-6) with fluorescent dopant materials. This composite approach enables the host to generate delayed fluorescence through TADF while the dopant provides stable emission at high current densities, solving both efficiency and productivity issues
2Use of energy by moving object
If TADF mechanism with small ΔST material is used as dopant, then internal quantum efficiency can be raised up to 100%, but roll-off occurs decreasing efficiency from 0.01 to 10 mA/cm2
Solution Approach 1:
The patent inverts the traditional approach by using the host material (not dopant) as the TADF-active component with small ΔST. This inversion allows the host to generate delayed fluorescence while the dopant provides stable emission, preventing efficiency roll-off at high current densities
Solution Approach 2:
The patent carefully controls the ΔST parameter of the host material within 0.0-0.3 eV range and adjusts dopant concentration (0.1-10 wt%) to optimize both internal quantum efficiency and current density stability, eliminating roll-off while achieving 100% efficiency
3Use of energy by moving object
If fluorescent dopant material is used in emitting layer, then light emission efficiency can be enhanced, but efficiency limitations persist in high current density areas
Solution Approach 1:
The host material acts as an intermediary that converts triplet excitons to singlet excitons via TADF mechanism, then transfers energy to the fluorescent dopant. This intermediary role enables efficient light emission at low current densities while the dopant ensures stable emission at high current densities, resolving the productivity limitation
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 proposed organic electroluminescence device achieves efficient light emission even in high-current-density areas, addressing the efficiency limitations of previous technologies.
Implementation Method 1
When voltage is applied on an organic electroluminescence device, holes and electrons are respectively injected into an emitting layer from an anode and a cathode. The injected holes and electrons are recombined in the emitting layer to form excitons.
Implementation Method 2
The TTF mechanism utilizes a phenomenon in which singlet excitons are generated by collision between two triplet excitons.
Implementation Method 3
The TADF mechanism utilizes a phenomenon in which inverse intersystem crossing from triplet excitons to singlet excitons is generated by using a material having a small energy gap (ΔST) between the singlet level and the triplet level.
Implementation Method 4
inverse intersystem crossing from triplet excitons to singlet excitons is generated by using a material having a small energy gap (ΔST) between the singlet level and the triplet level
Implementation Method 5
In the classification according to the emission principle, in a fluorescent EL device which uses emission caused by singlet excitons
Data Source
AI summary
An organic electroluminescence device includes: a cathode; an anode; and an organic thin-film layer disposed between the cathode and the anode, the organic thin-film layer having one or more layers including an emitting layer, in which the emitting layer includes a first material represented by the following formula (1) and a second material in a form of a fluorescent dopant material.