OLED Cathode Segmentation for Brightness Uniformity
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Solution Overview
Problem
Top emission type OLED display devices face issues with non-uniform brightness due to high resistance in the cathode, which is necessary for light emission but slows down current flow and causes brightness inconsistencies.
Innovation Solution
The OLED display device incorporates a thin film transistor, insulating layers, connecting and auxiliary electrodes, an anode, bank layer, and a cathode connected to a second auxiliary electrode to reduce cathode resistance, with the auxiliary electrodes forming a double-layered structure to enhance conductivity and uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the cathode is made thin to enable light emission in top emission type OLED, then the thin profile is achieved, but the cathode resistance increases causing non-uniform brightness
Solution Approach 1:
The cathode is divided into multiple segments: a first cathode layer (thin, for light emission) and a second cathode layer (thicker, for low resistance). This segmentation allows each layer to fulfill its specific function - the first layer enables top emission while the second layer ensures uniform current distribution and brightness
Solution Approach 2:
The cathode uses a composite structure with two different metal layers having complementary properties. The first cathode layer uses a material optimized for light emission transparency, while the second cathode layer uses a material optimized for electrical conductivity, creating a composite cathode that achieves both thin profile and low resistance
2Illumination intensity
If the cathode thickness is reduced for light emission, then top emission is enabled, but current flow slows down due to high resistance
Solution Approach 1:
The cathode is segmented into two functional layers: the first cathode layer (thin) handles light emission by being transparent to emitted light, while the second cathode layer (thicker) handles current transport by providing low electrical resistance, thus separating the optical function from the electrical function
Solution Approach 2:
The composite cathode structure performs multiple functions simultaneously: the first layer provides light emission transparency while the second layer provides electrical conductivity, making the cathode both an optical component and an electrical conductor without compromise
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 reduces cathode resistance, improving brightness uniformity and fabrication efficiency, enabling the production of large-sized OLED displays with consistent performance.
Implementation Method 1
The organic emitting layer contacting the anode and the cathode emits a light
Data Source
AI summary
An organic light emitting diode display device, comprises: a thin film transistor on a substrate; a first insulating layer on the thin film transistor; a connecting electrode connected to the thin film transistor and a first auxiliary electrode on the first insulating layer; a second insulating layer on the connecting electrode and the first auxiliary electrode; an anode connected to the connecting electrode and a second auxiliary electrode spaced apart from the anode and connected to the first auxiliary electrode on the second insulating layer; a bank layer having a first contact hole exposing the anode and a second contact hole exposing the second auxiliary electrode on the anode and the second auxiliary electrode; an organic emitting layer on the anode in the first contact hole; and a cathode electrically connected to the second auxiliary electrode on the organic emitting layer.