Segmented Common Electrodes in Organic EL Displays
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Solution Overview
Problem
In organic EL display devices, increasing the thickness of the common electrode to reduce resistance leads to internal stress, cracking, and deposition damage, while also increasing the time for the deposition step.
Innovation Solution
A display device configuration with a first common electrode, a light transmissive layer, and a second common electrode, where the light transmissive layer is stacked between the first and second common electrodes, reducing the occurrence of cracks and deposition damage while achieving lower resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the thickness of the common electrode is increased to reduce resistance, then the lower resistance is achieved, but internal stress increases causing cracks and deposition damage
Solution Approach 1:
The common electrode is divided into multiple separate common electrodes (first common electrode, second common electrode, third common electrode) arranged in a matrix pattern. Each common electrode has a smaller individual area but collectively provides the necessary electrical conductivity. This segmentation reduces the thickness required for each individual electrode while maintaining overall low resistance, thereby preventing internal stress and cracking.
2Reliability
If the thickness of the common electrode is increased to reduce resistance, then the drive voltage is reduced, but the time for deposition step is increased
Solution Approach 1:
By dividing the common electrode into multiple smaller electrodes arranged in a matrix, the total deposition time is reduced compared to depositing a single thick electrode. The segmented structure achieves the required electrical conductivity with thinner individual layers, thereby reducing both deposition time and drive voltage while maintaining structural integrity.
Data Source
AI summary
A display device includes: pixel electrodes corresponding to pixels; an insulating layer provided so as to overlie peripheral edge portions of the pixel electrodes; a light-emitting layer provided so as to be stacked on and in contact with each of the pixel electrodes; a first common electrode stacked on the light-emitting layer so as to be in contact therewith and provided so as to overlie the insulating layer; a light transmissive layer stacked on the first common electrode above the pixel electrodes, the light transmissive layer avoiding stacking thereof on the first common electrode above the insulating layer; and a second common electrode stacked on the light transmissive layer above the pixel electrodes and stacked on the first common electrode so as to be in contact therewith above the insulating layer.