Organic Electroluminescence Device Molten Salt Light Emitting Layer
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Solution Overview
Problem
Current organic electroluminescent devices do not achieve sufficient light emitting efficiency despite the use of phosphorescent materials, and existing methods to improve efficiency are complex and costly, leading to high operating voltages and short device lifespan.
Innovation Solution
Incorporating molten salt, specifically imidazolium derivatives or polymer molten salts, into the light emitting layer to form a field induction charge separation layer, facilitating carrier injection and improving recombination efficiency of electrons and holes, thereby reducing operating voltage and enhancing device lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If phosphorescent materials are used to form the light emitting layer, then internal quantum efficiency can reach 100%, but sufficient light emitting efficiency required in light emitting devices is not yet available
Solution Approach 1:
The patent uses a composite material system consisting of phosphorescent materials doped in host materials to form the light emitting layer. This composite approach combines the high internal quantum efficiency of phosphorescent materials with the charge transport capabilities of host materials, achieving both efficient energy utilization and sufficient light emitting efficiency for practical devices
Solution Approach 2:
The patent employs doping methodology where phosphorescent materials are distributed at specific concentrations within host materials. This local quality approach allows optimization of both the emitting properties (from phosphorescent dopants) and the charge transport properties (from host materials) in different regions of the light emitting layer, achieving balanced performance
2Reliability
If specific polymer materials are used to improve charge transport capacity, then light emitting efficiency is improved, but the forming process becomes complicated and costs increase
Solution Approach 1:
The patent merges the light emitting function and charge transport function into a single integrated light emitting layer. By using host-guest doping systems where the host material provides charge transport and the phosphorescent guest provides light emission, the patent eliminates the need for separate charge transport layers, simplifying the device structure and manufacturing process while maintaining high light emitting efficiency
3Reliability
If charge generation layer is disposed in light emitting layer, then light emitting efficiency is improved, but multiple wavelength light emission occurs instead of single wavelength
Solution Approach 1:
The patent applies local quality by concentrating phosphorescent dopants in specific regions or at specific concentrations within the light emitting layer, ensuring that charge generation and recombination occur primarily at these doped sites. This localized approach maintains single-wavelength emission characteristics while achieving high light emitting efficiency, avoiding the multiple wavelength emission problem
4Reliability
If electrical and physical properties between metals and organic layers are improved, then light emitting efficiency is improved, but interfacial property control becomes more complex
Solution Approach 1:
The host materials in the light emitting layer serve as intermediaries between the electrodes and phosphorescent dopants. These host materials are selected to have appropriate energy levels and charge transport properties that facilitate efficient charge injection from electrodes and effective energy transfer to phosphorescent dopants, improving light emitting efficiency without requiring complex interfacial engineering
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 use of molten salt in the light emitting layer results in improved light emitting efficiency, lower operating voltage, and extended lifespan of organic electroluminescent devices, as demonstrated by the examples provided.
Implementation Method 1
it has been found that when a voltage is applied to an electrode layer, molten salt which is included in a light emitting layer forms a field induction charge separation layer on an interface between the light emitting layer and an adjacent layer thereby lowering a carrier injection barrier
Implementation Method 2
molten salt which is included in a light emitting layer forms a field induction charge separation layer on an interface between the light emitting layer and an adjacent layer thereby lowering a carrier injection barrier
Implementation Method 3
When a voltage is applied between the anode and the cathode, holes emitted by the anode move to the light emitting layer via the hole transport layer. Electrons are emitted by the cathode and move to the light emitting layer via the electron transport layer. In the light emitting layer, the carriers recombine to produce excitons. The excitons radiatively decay, emitting light corresponding to a band gap of the material used to form the light emitting layer.
Data Source
AI summary
Provided are a light emitting layer including molten salt and an organic electroluminescent device comprising the light emitting layer. When the organic electroluminescent device is operated, a field induction charge separation layer is formed in the light emitting layer including the molten salt and thus, carrier injection is improved, thereby providing a light emitting layer having improved light emitting efficiency. An organic electroluminescent device including the light emitting layer has low operating voltage and long lifespan.