Organic EL Charge Injection Layer Sputtering Efficiency
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Solution Overview
Problem
The existing methods for forming an electrode layer on a charge injection layer in organic electroluminescent (EL) devices using the sputtering method result in decreased luminescent efficiency due to changes in the interface composition and particle invasion, which affects charge injection efficiency.
Innovation Solution
Forming the charge injection layer with a higher proportion of matrix organic material initially and increasing the proportion of charge injectable metallic material towards the end, using the same vapor deposition source for both layers to maintain a consistent interface composition, and forming the electrode layer by sputtering on a mixed layer of matrix organic and charge injectable metallic materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the electrode layer is formed by the sputtering method, then the film formation speed is improved, but the luminescent efficiency deteriorates
Solution Approach 1:
A charge injection layer is formed on the organic layer before forming the electrode layer. This preliminary layer prevents direct contact between the sputtering process and the organic layer, protecting the organic layer from damage while allowing fast electrode formation by sputtering.
Solution Approach 2:
The charge injection layer acts as an intermediary between the organic layer and the electrode layer. It is composed of materials with both organic and metallic characteristics, serving as a buffer that protects the organic layer from sputtering damage while enabling efficient charge injection for high luminescent efficiency.
2Reliability
If the electrode layer is formed by the vapor deposition method, then the luminescent efficiency is maintained, but the film formation speed decreases
Solution Approach 1:
The charge injection layer is formed in advance on the organic layer, creating a protective interface that enables subsequent fast electrode formation by sputtering without compromising luminescent efficiency.
Solution Approach 2:
The charge injection layer serves as an intermediary that allows the electrode layer to be formed by fast sputtering method while maintaining the luminescent efficiency typically achieved only by slower vapor deposition methods.
3Temperature
If the sputtering method is used for electrode layer formation, then the heat load is reduced, but the interface composition changes and particle invasion occurs
Solution Approach 1:
The charge injection layer is formed before electrode deposition, creating a protective barrier that prevents sputtering particles from invading the organic layer while allowing the low-heat sputtering process to proceed.
Solution Approach 2:
The charge injection layer acts as an intermediary barrier between the sputtering process and the organic layer, preventing particle invasion and maintaining interface composition stability while enabling the use of low-heat sputtering method.
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 maintains luminescent efficiency equivalent to vapor deposition methods while allowing for faster film formation, preventing deterioration of luminescent efficiency even when the electrode layer is formed by sputtering.
Implementation Method 1
a charge injection layer having a thin film in which a matrix organic material and a charge injectable metallic material are mixed is formed on a surface of the organic layer
Implementation Method 2
an electrode layer is formed on a surface of the charge injection layer by a sputtering method
Data Source
Figure 1~2
Figure 3(a)~3(e)
Figure 4~5
AI summary
A technology is provided, which obtains an organic EL device free from any reduction in the luminescent efficiency, even if an electrode layer is formed on a surface of a charge injection layer by a sputtering method. An organic EL device 40, 160 of the present invention includes a first charge injection layer 23, 126, a first organic layer 24, 124, and a second charge injection layer 25, 128. The second charge injection layer 25, 128 is formed as a mixed layer in which a matrix organic material and a charge injectable metallic material are mixed. Even when the electrode layer 26 is formed on a surface of this second charge injection layer 25 by the sputtering method, the luminescent efficiency does not decrease.