Blue OLED Light Emitting Layer Evaporation for Efficiency
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Solution Overview
Problem
Current methods for manufacturing organic electroluminescence (EL) display units, particularly for blue light emitting layers, face challenges in achieving high light emitting efficiency and longevity, especially when using ink jet or nozzle coating methods, which are not suitable for large-scale production and have difficulties in patterning.
Innovation Solution
A method involving the formation of a hole transport layer made of low molecular material on the blue organic EL device using the coating method, followed by the evaporation of the blue light emitting layer over the entire area of the red and green light emitting layers, along with sequential deposition of electron transport, injection layers, and an upper electrode, improves the interface state and enhances light emitting efficiency and life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If ink jet method or nozzle coating method is used to form blue light emitting layer, then large display screen area can be realized, but light emitting efficiency and life of blue pixel are insufficient
Solution Approach 1:
The patent segments the manufacturing process into two distinct parts: using coating methods (ink jet or nozzle) for forming red and green light emitting layers, and using vacuum evaporation method for forming the blue light emitting layer. This segmentation allows each method to be optimized for its specific purpose - coating methods for large area coverage and vacuum evaporation for high performance blue emission.
Solution Approach 2:
The patent applies different material qualities and formation methods to different color regions. Specifically, low molecular materials are used for the blue light emitting layer to achieve high light emitting efficiency and long life, while polymer materials are used for red and green layers formed by coating methods. This local differentiation of material properties resolves the contradiction between large area feasibility and blue pixel performance.
2Reliability
If vacuum evaporation method is used to form blue light emitting layer, then light emitting efficiency and life are improved, but separate coating by using metal mask is difficult and facility manufacturing cost is high
Solution Approach 1:
The patent divides the manufacturing approach by color: red and green layers are formed separately using coating methods with metal masks, while the blue layer is formed using vacuum evaporation without requiring separate mask coating steps. This segmentation eliminates the manufacturing difficulty of separate blue coating while maintaining high blue pixel performance.
Solution Approach 2:
The patent makes the blue light emitting layer formation universal across the entire display area by using vacuum evaporation method that can deposit material uniformly over large areas without requiring complex mask alignment and separate coating operations for each pixel region.
3Reliability
If vacuum evaporation method is used for large panel manufacturing, then blue light emitting performance is improved, but facility manufacturing cost increases and mass production is not suitable
Solution Approach 1:
The patent segments the manufacturing strategy by applying vacuum evaporation method specifically to the blue light emitting layer formation, which constitutes only one part of the complete display structure. The majority of layers (electrodes, hole injection layers, hole transport layers, electron transport layers, electron injection layers) continue to use cost-effective coating methods, enabling mass production while achieving high blue pixel performance.
Solution Approach 2:
The patent applies the expensive vacuum evaporation method locally only where high performance is critical (blue light emitting layer), while using economical coating methods for all other layers. This localized application of high-cost technology maintains mass production feasibility while achieving the desired blue light emitting 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 approach improves the light emitting efficiency and life of blue pixels in organic EL display units, facilitating better integration with red and green pixels, and allows for cost-effective large-scale production by resolving patterning difficulties.
Implementation Method 1
forming a hole injection layer respectively for the red organic EL device, the green organic EL device, and the blue organic EL device on the lower electrode by coating method
Implementation Method 2
forming a blue light emitting layer made of a low molecular material on the whole area of the red light emitting layer, the green light emitting layer, and the hole transport layer for the blue organic EL device by evaporation method
Implementation Method 3
sequentially forming an electron transport layer, an electron injection layer, and an upper electrode on the whole area of the blue light emitting layer
Data Source
AI summary
A method of manufacturing an organic EL display unit and an organic EL display unit capable of improving light emitting efficiency and life of blue are provided. A hole injection layer are formed on a lower electrode. For a red organic EL device and a green organic EL device, a hole transport layer, a red light emitting layer, and a green light emitting layer made of a polymer material are formed. A hole transport layer made of a low molecular material is formed on the hole injection layer of a blue organic EL device. A blue light emitting layer made of a low molecular material is formed on the red light emitting layer, the green light emitting layer, and the hole transport layer for the blue organic EL device. An electron transport layer, an electron injection layer, and an upper electrode are sequentially formed on the blue light emitting layer.