White OLED Interlayer Segmentation for Triplet Extinction
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Solution Overview
Problem
Hybrid organic light-emitting diodes (OLEDs) face challenges in achieving high efficiency and long operating lifetime due to the extinction of triplet excitons, particularly in blue-fluorescent emitter layers, which affects the emission color and efficiency of white-emitting OLEDs.
Innovation Solution
Incorporating at least two non-emitting interlayers between the phosphorescent and fluorescent emitter layers, where one interlayer is adjacent to the phosphorescent emitter and the other to the blue-fluorescent emitter, allowing for a broader range of materials that maintain balanced charge transport and prevent triplet exciton extinction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single interlayer is used between the blue-fluorescent emitter layer and the phosphorescent emitter layer, then the device complexity is reduced, but the efficiency and operating lifetime are insufficient
Solution Approach 1:
The single interlayer is segmented into two distinct interlayers: a first interlayer (hole-transporting material) and a second interlayer (electron-transporting material). This segmentation allows each interlayer to perform its specialized function optimally, preventing triplet exciton extinction and improving both efficiency and operating lifetime without excessive complexity.
Solution Approach 2:
The two interlayers act as intermediary layers between the blue-fluorescent emitter layer and the phosphorescent emitter layer. These intermediary layers mediate the interaction between the two emitter types by providing appropriate charge transport pathways and preventing harmful energy transfer, thus resolving the contradiction between simplicity and performance.
2Ease of manufacture
If standard matrix and emitter materials are used in the blue-fluorescent emitter layer, then the ease of manufacture is improved, but triplet excitons are extinguished resulting in low efficiency
Solution Approach 1:
The first and second interlayers serve as intermediary protective layers that prevent the harmful interaction between the blue-fluorescent emitter layer and the phosphorescent emitter layer. These intermediaries allow standard materials to be used in the blue-fluorescent layer while blocking the pathway that would otherwise cause triplet exciton extinction, thus maintaining ease of manufacture while eliminating energy loss.
3Device complexity
If only one interlayer is used, then the device complexity is reduced, but the efficiency remains insufficient
Solution Approach 1:
The interlayer configuration is segmented into two functional layers with distinct roles: the first interlayer focuses on hole transport and the second on electron transport. This functional segmentation enables more efficient charge balance and prevents triplet exciton extinction, thereby significantly improving emission efficiency while keeping the overall device complexity manageable.
Solution Approach 2:
Each interlayer is assigned specific local qualities: the first interlayer has optimized hole-transporting properties and the second has optimized electron-transporting properties. This local quality optimization ensures that each region of the device performs its specific function with maximum efficiency, resolving the contradiction between simple structure and high efficiency.
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 significantly enhances efficiency and extends the operating lifetime of white-emitting OLEDs while allowing for precise color setting, achieving high efficiency without compromising the device's longevity.
Implementation Method 1
at least one layer having at least one phosphorescent dopant
Implementation Method 2
at least one layer having at least one fluorescent dopant
Implementation Method 3
organic electroluminescence device which comprises at least one layer having at least one phosphorescent dopant and at least one layer having at least one fluorescent dopant
Data Source
AI summary
The present invention relates to white-emitting organic electroluminescent devices which have at least one blue-fluorescent emitter layer and at least one phosphorescent emitter layer.