Blue OLED Emitting Layers Using Exciplex and Delayed Fluorescence
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Solution Overview
Problem
Existing organic light emitting diodes (OLEDs) face challenges with low luminous efficiency and short luminous lifespan, particularly due to the limitations of fluorescent materials and short-lived phosphorescent materials.
Innovation Solution
The OLEDs incorporate a first and second blue emitting layer with specific p-type and n-type hosts represented by Formulas 1 and 3, and 1 and 5 respectively, providing exciplex and delayed fluorescent properties, along with phosphorescent dopants, to enhance efficiency and lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If fluorescent materials are used in OLEDs, then the device can be operated at low voltage and consume less power, but the luminous efficiency is low because only singlet excitons (about 25%) are used to generate light while triplet excitons (75%) are lost as heat
Solution Approach 1:
The patent changes the photophysical parameters of the emitting layer by incorporating phosphorescent dopants that enable triplet exciton utilization through phosphorescence, converting the 75% previously lost as heat into useful light emission, thereby improving luminous efficiency without significantly increasing power consumption
Solution Approach 2:
The patent uses composite material systems combining fluorescent hosts with phosphorescent dopants (such as iridium or platinum complexes) to create hybrid emitting layers that leverage both singlet and triplet excitons, achieving high luminous efficiency by utilizing all generated excitons for light emission
2Loss of energy
If phosphorescent materials are used to improve luminous efficiency, then both triplet and singlet excitons can be utilized, but the luminous lifespan is too short for commercial use
Solution Approach 1:
The patent applies local quality by creating distinct emitting layers with different characteristics - using phosphorescent dopants in specific regions where high efficiency is needed while maintaining stable host materials throughout the structure that provide long-term operational stability, thus achieving both high efficiency and long lifespan
Solution Approach 2:
The patent introduces stable host materials as intermediaries that mediate between the phosphorescent dopants and the electrical excitation, protecting the phosphorescent materials from degradation while enabling efficient energy transfer, thereby extending luminous lifespan without sacrificing efficiency
3Device complexity
If a single blue emitting layer is used, then the device structure is simpler, but the luminous efficiency and lifespan are limited by the properties of conventional materials
Solution Approach 1:
The patent segments the blue emitting layer into multiple sub-layers with different phosphorescent dopants and host material combinations, allowing each segment to optimize for specific wavelength regions or efficiency requirements, thereby achieving high overall luminous efficiency while maintaining manageable structural complexity
Solution Approach 2:
The patent adds a compositional dimension to the emitting layer structure by incorporating multiple dopant types and host materials with different photophysical properties, creating a multi-dimensional material system that achieves superior efficiency without proportionally increasing structural complexity
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
This configuration improves the lifespan and efficiency of OLEDs by optimizing the host materials, allowing for enhanced performance and longevity.
Implementation Method 1
phosphorescent materials can show high luminous efficiency since they use both triplet excitons and singlet excitons in the luminous process
Implementation Method 2
one of the first and second blue emitting layers includes a first p-type host represented by Formula 1 and a first n-type host represented by Formula 3 to provide an exciplex property
Implementation Method 3
An OLED emits light when a voltage is applied by injecting electrons from a cathode as an electron injection electrode, and holes from an anode as a hole injection electrode, into an emitting material layer (EML), where the electrons are combined with the holes, generating an exciton, and which emits light as it transitions from an excited state to a ground state
Data Source
AI summary
An organic light emitting diode, and an organic light emitting device including the same are described. An organic light emitting diode includes a first electrode; a second electrode facing the first electrode; and a first emitting part including a first blue emitting material layer and positioned between the first and second electrodes, the first blue emitting material layer including a first blue emitting layer and a second blue emitting layer, wherein one of the first and second blue emitting layers includes a first p-type host represented by Formula 1 and a first n-type host represented by Formula 3 to provide an exciplex property, and the other one of the first and second blue emitting layers includes a second p-type host represented by Formula 1 and a second n-type host represented by Formula 5 to provide a delayed fluorescent property.