White OLED Device Using Blue Fluorescent Host for Carrier Balance
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Solution Overview
Problem
White organic electroluminescent devices face challenges with low operating life, color stability, and high manufacturing costs due to the use of transition metal complexes, and fluorescent materials offer low luminescence efficiency and poor electrical conductivity, leading to imbalanced carrier injection and distribution.
Innovation Solution
A white organic electroluminescent device with a simple structure comprising a substrate, an anode layer, a first light emitting layer with red and blue organic fluorescent materials, and a second light emitting layer with green and blue organic fluorescent materials, where the blue material acts as both an energy-sensitized and electron-type host material, optimizing carrier balance and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If transition metal complexes are used as luminescent materials, then luminescence efficiency and color tunability are improved, but operating life and color stability deteriorate
Solution Approach 1:
The patent extracts and removes transition metal complexes from the luminescent material system, replacing them with purely organic fluorescent materials. This extraction eliminates the reliability issues associated with metal complexes while maintaining luminescence functionality through carefully selected organic compounds with appropriate energy levels and emission characteristics.
Solution Approach 2:
The patent employs composite material design by combining multiple organic fluorescent materials with different emission colors (red, green, blue) in specific ratios within the luminescent layer. This composite approach achieves full-color white light emission while avoiding the use of transition metal complexes, thereby resolving the contradiction between luminescence efficiency and operating stability.
2Reliability
If fluorescent materials are used to replace transition metal complexes, then operating life and color stability are improved, but luminescence efficiency and electrical conductivity deteriorate
Solution Approach 1:
The patent optimizes parameters of organic fluorescent materials including molecular structure design, energy level alignment, and doping concentrations. By adjusting these parameters, the luminescence efficiency of pure organic materials is enhanced to approach or reach the levels previously achieved only with transition metal complexes, while maintaining the reliability advantages of metal-free materials.
Solution Approach 2:
The patent introduces host-guest systems where host materials act as intermediaries to facilitate energy transfer to guest fluorescent materials. This intermediary mechanism enhances the overall luminescence efficiency of the organic fluorescent system by improving carrier transport and energy transfer efficiency, thereby compensating for the inherently lower efficiency of fluorescent materials compared to phosphorescent metal complexes.
3Reliability
If fluorescent materials are used, then operating life is improved, but carrier injection and distribution balance deteriorates
Solution Approach 1:
The patent applies local quality optimization by selecting host and guest materials with specific local properties (energy levels, mobility, LUMO/HOMO values) that are tailored to achieve balanced carrier injection and distribution. Each material component is chosen with its local characteristics optimized for its specific function in the device architecture.
Solution Approach 2:
The patent systematically adjusts critical parameters including LUMO energy levels of host materials, doping concentrations of fluorescent guests, and layer thicknesses to optimize carrier balance. By changing these parameters, the device achieves simultaneous improvement in operating life and carrier distribution balance, overcoming the limitations of conventional fluorescent materials.
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 device achieves high efficiency, luminance, and operation stability with a balanced carrier distribution, simple structure, and low manufacturing costs, while maintaining spectral stability.
Implementation Method 1
a first energy-sensitized organic material and a second energy-sensitized organic material, wherein the first energy-sensitized organic material is a blue organic fluorescent material with matched energy level and energy; a second energy-sensitized organic material is a blue organic fluorescent material with matched energy level and energy
Implementation Method 2
When charges are injected into an organic film between an electron injection electrode (an anode) and a hole injection electrode (a cathode), electrons and holes are combined and then annihilated to produce light
Data Source
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AI summary
The present invention provides a white organic electroluminescent device, comprising: a substrate; an anode layer; a first light emitting layer formed from a red organic fluorescent material, a first energy-sensitized organic material and a first hole-type organic host material; a second light emitting layer formed from a green organic fluorescent material, a second energy-sensitized organic material and a second hole-type organic host material; and a cathode layer. As compared to prior art, a blue organic fluorescent material is used as luminescent material and energy-sensitized material in the present invention, which can effectively transfer photon energy to the red organic fluorescent material or the green organic fluorescent material. Meanwhile, the blue organic fluorescent material also has excellent electron transport capability, and it is doped in the light emitting layer at a high concentration. This is beneficial for balancing the distribution of holes and electrons in the light emitting region, and can confine the recombination of holes and electrons within the narrow region of the light emitting layer.