Stacked OLED Sub-Devices with Buffer and Doping Layers
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Solution Overview
Problem
Current organic light-emitting devices face inefficiencies in luminous efficiency and electron injection due to the low probability of electrons encountering holes and the movement of holes from the emission layer to the electron transport region, which affects the overall performance and longevity of the devices.
Innovation Solution
The proposed solution involves a stacked structure of sub-organic light-emitting devices with specific emission layers, buffer layers, and doping layers, where the buffer layer and doping layer on the common emission layer reduce the band gap between the emission layers and the electron transport region, facilitating electron injection and preventing hole movement, thereby enhancing efficiency and extending the device's lifetime.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a conventional organic light-emitting device structure is used, then the device can operate, but the luminous efficiency is low due to low probability of electrons encountering holes
Solution Approach 1:
The device is divided into multiple sub-organic light-emitting devices stacked together, each with dedicated emission layers for different colors (red, green, blue). This segmentation allows independent optimization of electron-hole recombination in each sub-device, improving overall luminous efficiency by ensuring efficient encounters in each segment rather than relying on a single mixed emission layer.
Solution Approach 2:
Buffer layers and doping layers are introduced as intermediary structures between the emission layers and electron transport regions. These intermediary layers facilitate better electron injection into emission layers while preventing hole leakage, thereby increasing the probability of electron-hole encounters and improving luminous efficiency.
2Reliability
If no buffer layer or doping layer is used, then the structure is simpler, but holes move from the emission layer to the electron transport region reducing device performance
Solution Approach 1:
Buffer layers and doping layers serve as intermediary structures positioned between emission layers and electron transport regions. These layers act as barriers that prevent hole movement from emission layers to electron transport regions, ensuring holes remain in emission layers for effective recombination. The intermediary layers are essential for maintaining device performance despite adding structural complexity.
Solution Approach 2:
Different layers (buffer layers and doping layers) are applied locally at specific positions within the device structure, particularly at interfaces between emission layers and electron transport regions. This local quality enhancement targets specific problem areas (hole leakage) without unnecessarily complicating the entire device structure, optimizing hole retention where it is most needed.
3Use of energy by moving object
If the band gap between emission layers and electron transport region is large, then charge separation is better, but electron injection is inefficient
Solution Approach 1:
The doping layers modify the energy level parameters of the electron transport region by introducing dopant materials with specific energy levels. This parameter change reduces the band gap between emission layers and electron transport region, facilitating efficient electron injection while maintaining adequate charge separation through controlled energy level alignment.
Solution Approach 2:
Doping layers act as intermediary structures that bridge the energy gap between emission layers and electron transport regions. By introducing intermediate energy levels through doping, electrons can more easily transition from emission layers to electron transport regions, improving injection efficiency without compromising the necessary energy difference for charge separation.
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 luminous efficiency and extends the lifetime of organic light-emitting devices by ensuring effective electron injection and retention of holes within the emission layers, leading to high efficiency and prolonged performance.
Implementation Method 1
The first emission layer may emit light having a wavelength range of about 620 nm to about 750 nm, the second emission layer may emit light having a wavelength range of about 495 nm to about 570 nm, and the first common emission part, the second common emission part, and the third common emission part may emit light having a wavelength range of about 440 nm to about 490 nm
Data Source
AI summary
An organic light-emitting device, including a first sub-organic light-emitting device including a first emission layer, a first common emission part, a first buffer part, a first doping part, and a first cathode part, sequentially stacked; a second sub-organic light-emitting device including a second emission layer, a second common emission part, a second buffer part, a second doping part, and a second cathode part, sequentially stacked; and a third sub-organic light-emitting device including a third common emission part, a third buffer part, a third doping part, and a third cathode part, sequentially stacked, the first through third common emission parts integrated with one another as one body, the first through third buffer parts integrated with one another as one body, the first through third doping parts integrated with one another as one body, and the first through third cathode parts integrated with one another as one body.