OLED Second Electrode Segmentation for Brightness Uniformity
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Solution Overview
Problem
The high resistance of the second electrode in organic light emitting display apparatuses leads to non-uniform brightness across pixel areas and increased power consumption, limiting the size of the display due to voltage drop and requiring selective etching that can damage the organic layer and reduce reliability.
Innovation Solution
A manufacturing method and apparatus where a bus electrode with lower resistance is connected to the second electrode without removing the organic layer, using a separation pattern with an inverted tapered cross-section to create a crevice for the connection, allowing the second electrode to be formed on the organic layer while avoiding damage to the organic layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the second electrode is made thin to increase light emission efficiency, then brightness is improved, but resistance increases causing non-uniform brightness and higher power consumption
Solution Approach 1:
The second electrode is segmented into multiple bus electrodes that are distributed across the display area. Each bus electrode is connected to the power source independently, allowing the electrical path to be divided into multiple parallel paths. This segmentation reduces the resistance of each individual path and ensures uniform brightness distribution across the display panel.
2Reliability
If a bus electrode is added to reduce resistance, then brightness uniformity is improved, but the organic layer must be selectively etched which damages the layer and reduces reliability
Solution Approach 1:
The connection between bus electrodes and the second electrode is achieved in the vertical dimension through a crevice structure rather than by etching the organic layer horizontally. The crevice is formed by controlling the deposition process to create an exposed portion of the bus electrode that extends vertically, allowing the second electrode to contact the bus electrode through this crevice without removing the organic layer.
3Area of stationary object
If the area of the organic light emitting display apparatus is increased, then display size is improved, but voltage drop and power consumption increase due to higher resistance of the second electrode
Solution Approach 1:
The second electrode is divided into multiple bus electrodes distributed across the display area, creating multiple parallel electrical paths. This segmentation reduces the total resistance of the second electrode by providing multiple conduction paths, thereby reducing voltage drop and power consumption in large-area displays.
Solution Approach 2:
Multiple bus electrodes are connected to the power source at the same potential, creating equipotential regions across the display area. This ensures that voltage distribution remains uniform across large areas, preventing excessive voltage drop even as display size increases.
Data Source
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Figure 3A~3B
AI summary
An organic light emitting display apparatus includes a plurality of pixel areas, each pixel area comprising an emission area and a non-emission area; a first electrode formed in the emission area; a bus electrode formed in the non-emission area; an adherent pattern formed on a portion of the bus electrode; a separation pattern formed on at least a portion of the adherent pattern, the separation pattern having an inverted tapered shape; an organic layer formed on the first electrode, and the separation pattern, the organic layer comprising an emission layer, and a second electrode formed on the organic layer and on a portion of the bus electrode exposed by the separation pattern, and the second electrode electrically contacting the bus electrode.