OLED Pixel Definition Pits to Block Lateral Leakage Current
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Solution Overview
Problem
The use of shadow masks in OLED display devices leads to sagging, reducing yield, and the formation of common layers without separation results in lateral leakage currents due to continuous current flow through the common layer, causing performance issues.
Innovation Solution
Introducing pits or spacers between subpixels to separate the common layer and the cathode electrode, thereby preventing lateral leakage currents and improving device performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If shadow mask is used for forming organic light-emitting layer, then manufacturing precision is improved, but device reliability deteriorates due to sagging and reduced yield
Solution Approach 1:
The patent removes the shadow mask component from the manufacturing process entirely. Instead of using a shadow mask to define pixel patterns, the invention forms the common organic layer continuously across the substrate and uses pixel definition layers and protrusions to subsequently define the light-emitting regions, thereby eliminating shadow mask sagging and associated yield losses.
Solution Approach 2:
The patent divides the organic layer formation into two distinct parts: a common organic layer formed continuously across the entire substrate, and a light-emitting layer formed only in specific pixel regions using pixel definition layers. This segmentation allows the common layer to be formed without shadow masks while still achieving precise pixel patterning through the pixel definition structure.
2Device complexity
If common layer is continuously formed without separation, then device complexity is reduced, but harmful factors increase due to lateral leakage current
Solution Approach 1:
The patent introduces pixel definition layers and protrusions as intermediary structures between the common organic layer and the electrodes. These intermediaries physically separate the common layer in different pixel regions, blocking the lateral movement of charge carriers while maintaining the continuous common layer structure for simplified manufacturing.
Solution Approach 2:
The patent segments the common organic layer's electrical connectivity by introducing pixel definition layers that create electrical isolation between adjacent pixels. Although the common layer is physically continuous, the pixel definition layers divide it into electrically independent regions, preventing lateral leakage current while maintaining structural simplicity.
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
The implementation of pits or spacers effectively isolates the common organic layer from the cathode electrode, reducing lateral leakage currents and enhancing the overall efficiency and yield of OLED display devices.
Implementation Method 1
When the two electrodes inject electrons and holes into the organic light-emitting layer, electrons and holes recombine to form excitons, and the excitons transition from an excited state to a ground state so as to emit light.
Data Source
AI summary
A display device including a substrate which has a plurality of pixels each including an emission portion and a non-emission portion, a first electrode which is disposed on the emission portion, a pixel definition layer which is disposed on an edge of the first electrode and the non-emission portion, a common organic layer which is disposed on the first electrode and the pixel definition layer, an organic light-emitting layer which is disposed on the common organic layer and overlaps the emission portion, and a second electrode which is disposed on the common organic layer and the organic light-emitting layer. The pixel definition layer includes a plurality of pits between adjacent pixels. The common organic layer and the second electrode are separated by the pits.