OLED Emitter Layers with Controlled Charge Mobility
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Solution Overview
Problem
Current OLEDs face challenges in achieving high luminous efficiency and lifespan due to limitations in exciton recombination and charge transport, particularly with fluorescent materials and short-lived phosphorescent metal complexes.
Innovation Solution
An OLED structure with a red, yellow-green, and green emitting material layer, each incorporating hosts with controlled charge mobility, is developed, allowing for uniform exciton recombination and reduced exciton quenching, thereby enhancing luminous efficiency and lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If fluorescent materials are used in OLED, then the device can be operated, but luminous efficiency is low because only singlet excitons are utilized
Solution Approach 1:
The patent employs a composite emitting layer structure combining fluorescent and phosphorescent materials in specific layers. The red and green emitting layers use fluorescent hosts with phosphorescent dopants, while the yellow-green layer uses a phosphorescent host. This composite approach enables simultaneous utilization of singlet and triplet excitons across different layers, achieving high luminous efficiency while maintaining device stability.
2Use of energy by moving object
If phosphorescent metal complexes are used to improve luminous efficiency, then triplet excitons can be utilized, but luminous lifespan becomes too short for commercial use
Solution Approach 1:
The patent applies local quality by assigning different material characteristics to different emitting layers. The red and green layers use fluorescent hosts that provide long lifespan, while the yellow-green layer uses phosphorescent material optimized for efficiency. This spatial differentiation of material properties allows the device to achieve high overall efficiency without sacrificing lifespan, as the phosphorescent material is localized to where it provides maximum benefit.
Solution Approach 2:
The patent changes the parameters of phosphorescent materials by selecting specific hosts and dopants with optimized properties. The yellow-green phosphorescent layer uses a host with specific triplet energy levels and the red/green layers use phosphorescent dopants with tailored lifetimes. By carefully controlling these parameters, the device achieves high efficiency while the overall phosphorescent content remains limited to preserve lifespan.
3Illumination intensity
If exciton recombination is concentrated in specific layers, then emission can be intense, but exciton quenching increases and causes material degradation
Solution Approach 1:
The patent segments the emitting layer into three distinct layers (red, yellow-green, green) with different material compositions and exciton recombination characteristics. This segmentation distributes exciton generation and recombination across multiple layers rather than concentrating it in one layer, reducing exciton density in each individual layer and minimizing quenching effects and material degradation while maintaining overall emission intensity.
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 solution enables OLEDs to operate at low power consumption with improved luminous efficiency and extended lifespan by distributing exciton recombination uniformly across the emitting material layers, minimizing degradation and quenching.
Implementation Method 1
the first red host has an electron mobility in a range between about 1E-04 cm2/V·S and about 1E-03 cm2/V·S, the first yellow-green host has a hole mobility in a range between about 5E-08 cm2/V·S and about 1E-05 cm2/V·S, and the first green host has a hole mobility in a range between about 3E-05 cm2/V·S and about 1E-4 cm2/V·S
Implementation Method 2
An organic light emitting diode (OLED) can be driven at low power consumption and have beneficial luminous efficiency and/or luminous luminance
Data Source
AI summary
An organic light emitting diode (OLED) and an organic light emitting device comprising the OLED (e.g., a display device or a lighting device) are described. The OLED includes a red emitting material layer, a yellow-green emitting material layer and a green emitting material layer each of which includes a host with controlled charge mobility between two electrodes. The OLED and the organic light emitting device can secure wide emission area and have beneficial luminous lifespan.