OLED Storage Capacitor Overlap and Moisture Barrier
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In organic electroluminescent devices (OLEDs), reducing the size of pixel regions to achieve higher resolution leads to a decrease in storage capacitance and aperture ratio, and flexible OLEDs face issues with moisture and oxygen permeation, static electricity, and TFT malfunction.
Innovation Solution
The OLED design includes a storage capacitor that overlaps switching and driving TFTs, using a metal material for electrodes and inorganic insulating materials for buffer layers, and incorporates a moisture blocking layer on a flexible substrate to prevent degradation and improve capacitance and aperture ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the pixel region size is reduced to achieve higher resolution, then the resolution is improved, but the storage capacitance and aperture ratio decrease
Solution Approach 1:
The storage capacitor is repositioned from a planar configuration to a three-dimensional structure that overlaps with the TFT in the vertical dimension. This allows the capacitor to utilize the space above and below the TFT layer, effectively increasing its area without expanding the pixel region footprint, thereby maintaining high resolution while increasing storage capacitance.
Solution Approach 2:
The storage capacitor is nested within the pixel region by positioning it to overlap with the TFT structure. The capacitor's electrodes are arranged such that one electrode is formed on the TFT structure while the other is formed on the opposite side, creating a nested configuration that maximizes space utilization within the constrained pixel area.
2Measurement precision
If the pixel region size is reduced to achieve higher resolution, then the resolution is improved, but the aperture ratio decreases
Solution Approach 1:
By moving the storage capacitor into the vertical dimension through overlapping with the TFT, the horizontal area available for light emission is preserved. This dimensional transition allows the aperture ratio to remain high while the resolution is improved through smaller pixel pitch.
3Adaptability or versatility
If a flexible substrate is used to enable flexible OLED, then the flexibility is improved, but moisture and oxygen permeation increases causing TFT malfunction
Solution Approach 1:
A moisture blocking layer is introduced as a thin film structure between the flexible substrate and the TFT. This film acts as a barrier to moisture and oxygen permeation, protecting the TFT from environmental degradation while maintaining the overall flexibility of the device.
Solution Approach 2:
The moisture blocking layer serves as an intermediary between the flexible substrate and the TFT. It mediates the interaction by blocking harmful moisture and oxygen molecules from reaching the TFT, thereby preventing malfunction while allowing the flexible substrate to maintain its mechanical properties.
Data Source
Figure 1
Figure 2~3
Figure 4A~4B
AI summary
Disclosed is an organic electroluminescent device (OELD) (100) that includes a first substrate (101) including a pixel region (P) that includes an element region (DA) and a light emission region (EA); a storage capacitor (StgC) disposed at the element region (DA), and including a first storage electrode (103), a first buffer layer (104) on the first storage electrode (103), and a second storage electrode (106) on the first buffer layer (104); a second buffer layer (108) on the storage capacitor (StgC); a plurality of TFTs (STr, DTr) on the second buffer layer (108) at the element region (DA); and a passivation layer (160) on the plurality of TFTs (STr, DTr), wherein the storage capacitor (StgC) overlaps at least one of the plurality of TFTs (STr, DTr).