Organic EL Upper Electrode Conductivity via Merged Auxiliary Interconnects
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Solution Overview
Problem
In organic EL display devices with a top-emission structure, the high sheet resistance of the upper electrode leads to voltage drops, which complicates the arrangement of sub-pixels and reduces the aperture ratio and display definition due to the need for auxiliary interconnects and contacts that occupy space, limiting the density and size of the pixel array.
Innovation Solution
The display device arranges sub-pixels in a matrix with a common upper electrode connected to auxiliary interconnects, reducing the number of auxiliary interconnect contacts between adjacent sub-pixels, allowing for closer packing and higher density by grouping sub-pixels and forming fewer auxiliary interconnect contacts, thereby decreasing the upper electrode's resistance and enhancing aperture ratio and display definition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If auxiliary interconnects and contacts are added to reduce upper electrode resistance, then electrical conductivity is improved, but device complexity and space occupation increase, reducing aperture ratio and pixel density
Solution Approach 1:
The patent combines the auxiliary interconnect function with the existing pixel electrode structure by making the pixel electrode extend to the edge of the organic EL element and serve as the auxiliary interconnect. This integration eliminates separate auxiliary interconnect structures while maintaining the electrical conductivity function, thereby reducing device complexity and space occupation.
Solution Approach 2:
The pixel electrode is designed to perform multiple functions: it serves as both the electrical connection terminal and the auxiliary interconnect for reducing resistance. This multi-functionality eliminates the need for dedicated auxiliary interconnect structures, reducing overall device complexity while maintaining improved electrical conductivity.
2Reliability
If auxiliary interconnect contacts are placed between adjacent sub-pixels, then upper electrode resistance is reduced, but pixel density and aperture ratio decrease due to space occupation
Solution Approach 1:
The patent merges the auxiliary interconnect contact function with the pixel electrode itself by extending the pixel electrode to the edge of the organic EL element. This eliminates the need for separate auxiliary contacts between sub-pixels, freeing up space that can be used to increase pixel density and aperture ratio while maintaining the conductivity improvement.
3Area of moving object
If pixel electrodes are extended to edge of organic EL elements, then aperture ratio is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent designs the pixel electrode to extend to the edge of the organic EL element, creating an equipotential surface that serves both as the electrical connection and auxiliary interconnect. This design simplifies the manufacturing process by reducing the number of precise alignment steps needed, as the extended electrode naturally provides the necessary electrical pathways without requiring additional precision positioning of separate components.
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 enables a higher density of sub-pixels, improved aperture ratio, and enhanced display definition by reducing the space required for auxiliary interconnects, thus increasing the pixel area and extending the life of the organic EL elements.
Implementation Method 1
The organic EL element is a so-called current-driven electro-optical element whose light emission luminance varies depending on the value of the current that flows through the element, and is based on a phenomenon that light emission occurs in response to electric field application to an organic thin film
Data Source
AI summary
A display device including: a plurality of sub-pixels arranged in a matrix, each including an electro-optical element having a structure in which a display functional layer is sandwiched between an upper electrode and a lower electrode; and an auxiliary interconnect contact in a pixel area in which the plurality of sub-pixels are arranged in a matrix and electrically connecting the upper electrode to an auxiliary interconnect, wherein m (m is an integer equal to or larger than two) sub-pixels adjacent to each other along an arrangement direction of the sub-pixels are regarded as one group, and n (n is a natural number smaller than m) auxiliary interconnect contacts are formed for each group.