OLED Pixel Electrode Segmentation for Luminance and Cost
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Solution Overview
Problem
Organic light-emitting display (OLED) devices manufactured using photo patterning processes suffer from reduced luminance due to the deposition of a cathode electrode twice, which affects light characteristics, increasing manufacturing costs and reducing desired light output.
Innovation Solution
The OLED device design includes a substrate with a pixel electrode, a pixel-defining layer, an intermediate layer with a central and edge portion, a protective layer, and an opposite electrode that is electrically connected to the protective layer, eliminating the need for an opposite electrode over the central portion of the light emitting intermediate layer, thereby reducing residual material and maintaining light characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If photo patterning process is used for depositing organic emission layer, then manufacturing cost is reduced, but light characteristics (luminance) are degraded
Solution Approach 1:
The cathode electrode is segmented into two parts: a first cathode electrode deposited over the entire intermediate layer, and a second cathode electrode deposited only in the non-emission area. This segmentation allows the emission area to remain free of residual material that would degrade luminance, while still providing complete cathode coverage for electrical functionality.
Solution Approach 2:
Different regions of the device are given different qualities: the emission area has no cathode electrode material to maintain high luminance, while the non-emission area has the cathode electrode for proper electrical connection. This local differentiation resolves the contradiction between manufacturing simplicity and light output quality.
2Reliability
If opposite electrode is deposited over the entire intermediate layer, then electrical connection is ensured, but residual material degrades light characteristics
Solution Approach 1:
The cathode electrode structure is divided into two segments: a first cathode electrode that provides baseline coverage, and a second cathode electrode that is selectively deposited only in the non-emission area. This segmentation ensures electrical connection is maintained while preventing residual material from degrading light characteristics in the emission area.
Solution Approach 2:
Instead of depositing the cathode electrode uniformly across the entire device and then removing material from the emission area (which would be complex), the approach is inverted: deposit the cathode electrode only where needed (non-emission area) and leave the emission area clear. This inverse approach simplifies the process while achieving the same functional result.
3Illumination intensity
If fine metal mask is used for deposition, then desired light characteristics are achieved, but manufacturing cost increases
Solution Approach 1:
The complex fine metal mask step is extracted and replaced by a simpler selective deposition process. The first cathode electrode is deposited using a simple mask, then the second cathode electrode is selectively deposited only in the non-emission area using photo patterning, eliminating the need for expensive fine metal masks while maintaining light characteristics.
Data Source
AI summary
A method of manufacturing an organic light-emitting display apparatus includes: forming a pixel electrode on a substrate; forming a pixel-defining layer (PDL) having an opening exposing at least a part of the pixel electrode; forming an intermediate layer including a central portion disposed on the pixel electrode, an edge portion that extends from the central portion and contacts the PDL, at least one common layer, and an organic emission layer; forming a protective layer including a central portion disposed on the central portion of the intermediate layer and an edge portion that extends from the central portion of the protective layer and contacts the PDL; and forming an opposite electrode on the PDL, the opposite electrode having an opening exposing at least a part of the protective layer and electrically connected to the protective layer.