OLED Charge Control Layer for Balanced Luminous Efficiency
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Solution Overview
Problem
Existing OLEDs face limitations in achieving balanced luminous efficiency and lifespan, particularly due to the degradation of red emitting materials and the vulnerability of blue emitting materials to holes, leading to inefficient exciton utilization and reduced luminous lifespan.
Innovation Solution
Incorporating a charge control layer with controlled hole mobility and a highest occupied molecular orbital (HOMO) energy level between the red and blue emitting material layers, which includes organic compounds with specific structures, to manage hole mobility and prevent excessive exciton quenching, thereby stabilizing both red and blue luminous efficiencies and extending lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If phosphorescent materials are used to improve luminous efficiency, then luminous efficiency is improved, but luminous lifespan is reduced
Solution Approach 1:
The emissive layer is divided into multiple sub-layers with different emitting materials (red, green, blue) and each sub-layer is equipped with dedicated charge control layers. This segmentation allows each material to operate under optimized charge conditions, preventing degradation while maintaining high efficiency.
Solution Approach 2:
Charge control layers with specific hole mobility (1.0E-11 to 1.0E-5 cm2/V·S) and HOMO energy levels (−6.5 eV to −5.9 eV) are introduced as intermediary layers between electrodes and emitting material layers. These layers mediate charge transport, preventing excessive hole accumulation that would otherwise degrade the phosphorescent materials.
2Use of energy by moving object
If red emitting material layer is used, then red luminous efficiency is improved, but red emitting material degrades
Solution Approach 1:
A charge control layer with specifically controlled hole mobility (1.0E-11 to 1.0E-5 cm2/V·S) and HOMO energy level (−6.5 eV to −5.9 eV) is positioned between the anode and the red emitting material layer. This intermediary layer prevents excessive hole injection directly to the red emitting material, reducing degradation while preserving luminous efficiency.
3Use of energy by moving object
If blue emitting material layer is used, then blue luminous efficiency is improved, but blue emitting material is vulnerable to holes
Solution Approach 1:
Charge control layers with controlled hole mobility and HOMO energy levels are positioned between the red emitting material layer and the blue emitting material layer, and between the blue emitting material layer and the cathode. These intermediary layers regulate hole transport, preventing excessive holes from reaching the blue emitting material while maintaining efficient exciton utilization.
4Device complexity
If known fluorescent materials are used, then device structure is simple, but luminous efficiency is low
Solution Approach 1:
The emissive layer is segmented into multiple functional sub-layers (red emitting material layer, green emitting material layer, blue emitting material layer) with dedicated charge control layers for each. This segmented structure enables the use of phosphorescent materials that require precise charge control, achieving higher luminous efficiency while maintaining manageable device complexity through modular design.
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 effectively maintains stable red luminous efficiency and extends the lifespan of blue emitting materials by minimizing exciton loss and degradation, ensuring balanced luminous performance and improved OLED durability.
Implementation Method 1
the charge control layer includes an organic compound having a hole mobility ranging from about 1.0E−11 cm2/V·S to about 1.0E−5 cm2/V·S
Implementation Method 2
a highest occupied molecular orbital energy level ranging from about −6.5 eV to about −5.9 eV
Implementation Method 3
OLEDs can be driven at lower voltages than LCDs, and OLEDs have exhibit advantageously high color purity compared to LCDs
Implementation Method 4
phosphorescent materials can show higher luminous efficiency because they use triplet excitons as well as singlet excitons in the luminous process
Data Source
AI summary
An organic light emitting diode (OLED) and an organic light emitting device including the OLED (e.g., a display device or a lighting device) are disclosed herein. An emissive layer disposed between two electrodes includes a charge control layer with controlled hole mobility and/or a HOMO energy level between a red emitting material layer and a blue emitting material layer. The blue luminous efficiency can be improved and exciton recombination zone is formed within an emitting material layer by injecting holes and electrons into the emitting material layer in balance. As the luminous efficiency of red and blue lights is controlled in balance, beneficial blue luminous efficiency and excellent red luminous efficiency can be realized.