Auxiliary Cathode Electrode for Uniform OLED Brightness
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Solution Overview
Problem
Large area organic light emitting diode displays face issues with uneven brightness and luminance due to high surface resistance of cathode electrodes made from transparent conductive materials like indium-tin-oxide or indium-zinc-oxide, leading to non-uniform voltage distribution.
Innovation Solution
Incorporation of an auxiliary cathode electrode made of metal material with lower specific resistance, such as silver, and a protective electrode to reduce surface resistance and prevent damage during manufacturing, ensuring uniform voltage distribution across the display panel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If transparent conductive materials like indium-tin-oxide or indium-zinc-oxide are used for cathode electrodes, then transparency is improved, but surface resistance increases leading to non-uniform voltage distribution
Solution Approach 1:
The patent applies composite materials by combining transparent conductive materials (for transparency) with metal materials having lower specific resistance (for conductivity) in a layered cathode electrode structure. This composite approach allows the electrode to simultaneously achieve both transparency and low surface resistance, resolving the contradiction between these two properties.
2Reliability
If metal material with lower specific resistance is used for auxiliary cathode electrode, then surface resistance is reduced, but vulnerability to damage during manufacturing increases
Solution Approach 1:
The patent implements beforehand cushioning by introducing a protective electrode layer that covers and protects the auxiliary cathode electrode made of metal material before and during subsequent manufacturing processes. This protective layer prevents damage to the vulnerable metal electrode while maintaining its low resistance function.
Solution Approach 2:
The protective electrode acts as an intermediary element between the auxiliary cathode electrode and the external environment/manufacturing processes. It mediates the protection function, shielding the metal electrode from mechanical damage while allowing the electrical function to proceed.
3Area of stationary object
If large area display is implemented, then display size is increased, but brightness uniformity deteriorates due to high surface resistance
Solution Approach 1:
The patent uses composite materials in the cathode electrode structure, combining transparent conductive materials with metal materials having lower specific resistance. This composite approach reduces overall surface resistance across the large display area, enabling uniform voltage distribution and consistent brightness across the entire large area display.
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 solution effectively lowers the surface resistance of the cathode electrode, maintaining uniform brightness and luminance across the large area organic light emitting diode display by ensuring uniform voltage distribution and protecting the auxiliary cathode electrode from damage.
Implementation Method 1
Incorporation of an auxiliary cathode electrode made of metal material with lower specific resistance, such as silver, and a protective electrode to reduce surface resistance and prevent damage during manufacturing, ensuring uniform voltage distribution across the display panel
Data Source
AI summary
A large area organic light emitting diode display is provided. The organic light emitting diode display comprises a substrate including a display area defining a plurality of pixel areas in a matrix manner and a non-display area surrounding the display area; a thin film transistor disposed in each pixel area; an auxiliary cathode electrode disposed at the same layer with an element of the thin film transistor; a planar layer on the thin film transistor and the auxiliary cathode electrode; an anode electrode connected to the thin film transistor and disposed in each pixel area on the planar layer; an organic light emission layer disposed on the anode electrode; a cathode electrode covering the whole surface of the display area on the organic light emission layer; and a protective electrode covering the auxiliary cathode electrode exposed through a cathode contact hole and contacting the cathode electrode.