Quantum Dot Emitting Structure With Dual Transparent Electrodes
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Solution Overview
Problem
Conventional quantum dot light-emitting devices face challenges in achieving high light exiting efficiency and uniformity due to insufficient film thickness uniformity and microcavity structure control when using inorganic materials in solution processes.
Innovation Solution
A quantum dot light-emitting device with a stacked structure comprising a first electrode layer, a quantum dot light-emitting layer, an electron transport layer, a second transparent electrode layer, and a third transparent electrode layer, where the second electrode layer has a lower oxygen content and thinner than the third, facilitating electron injection and improving transmittance and light extraction efficiency. The layers are deposited using sputtering with controlled oxygen and inert gas flows to optimize work functions and film thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If inorganic materials are used in solution processes to form transparent electrode layers, then the device structure can be simplified, but the film thickness uniformity and microcavity structure control are insufficient
Solution Approach 1:
The patent changes the deposition method from solution process to sputtering process, and adjusts sputtering parameters (oxygen flow rate, power, pressure) to control film thickness uniformity and work function. This parameter optimization resolves the contradiction by achieving precise thickness control while maintaining device structure simplicity.
Solution Approach 2:
The patent uses composite transparent electrode structures with multiple layers (e.g., ITO/IZO/ITO) where each layer has specific thickness and composition optimized for different functions. This composite approach enables both good film uniformity and controlled microcavity effects, resolving the manufacturing precision issue while keeping the overall device structure manageable.
2Illumination intensity
If the top transparent electrode layer has high transmittance to improve light exiting efficiency, then the work function may not match the electron transport layer LUMO level, but electron injection efficiency decreases
Solution Approach 1:
The patent applies different local properties to different parts of the transparent electrode structure. The bottom transparent electrode layer has work function optimized for electron injection (matching LUMO level), while the top layer has higher transmittance for light extraction. This local differentiation resolves the contradiction between electron injection efficiency and light exiting efficiency.
Solution Approach 2:
The patent employs composite transparent electrode layers with different materials (ITO, IZO) and different thicknesses to achieve both required work functions and transmittance levels. The multi-layer composite structure allows simultaneous optimization of electron injection (at the interface with electron transport layer) and light extraction (at the top surface).
3Device complexity
If a single transparent electrode layer is used to simplify the device structure, then the work function control and transmittance optimization become difficult
Solution Approach 1:
The patent divides the transparent electrode into multiple layers with different local properties - each layer has specific thickness, composition, and work function optimized for its position and function. This allows independent optimization of electron injection (bottom layer) and light extraction (top layer) without compromising overall device simplicity.
Solution Approach 2:
The patent segments the transparent electrode function into multiple distinct layers, where the bottom layer handles electron injection and the top layer handles light extraction. This segmentation allows each layer to be independently optimized for its specific function, providing adaptability in work function control while maintaining a relatively simple overall structure.
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 device exhibits enhanced light-emitting performance and higher light exiting efficiency compared to conventional structures, with improved transmittance and current efficiency, overcoming defects in microcavity structure control and film uniformity.
Implementation Method 1
The layers are deposited using sputtering with controlled oxygen and inert gas flows to optimize work functions and film thickness
Data Source
AI summary
The present disclosure relates to the technical field of display, and discloses a quantum dot light-emitting device and a preparation method thereof. The quantum dot light-emitting device includes a first electrode layer, a quantum dot light-emitting layer, an electron transport layer, a second electrode layer and a third electrode layer which are sequentially arranged in a stacked manner, wherein the side, facing away from the first electrode layer, of the third electrode layer is configured as a light exiting side; the second electrode layer and the third electrode layer are transparent electrode layers; and the work function of the second electrode layer is greater than the LUMO energy level of the electron transport layer and smaller than the work function of the third electrode layer.