OLED Common Hole Layer Shorted to Bias Path
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Solution Overview
Problem
Organic light-emitting diode displays face issues with lateral leakage currents due to doping levels in the hole layer, causing adjacent pixels to turn on inadvertently, which affects image accuracy and efficiency.
Innovation Solution
A common hole layer is shorted to a metal bias path, which is interposed between adjacent pixels, maintaining a voltage less than ground voltage to block lateral leakage currents, thereby isolating each pixel and preventing unwanted activation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a common hole layer is used in organic light-emitting diode displays, then manufacturing is simplified and device complexity is reduced, but lateral leakage currents occur between adjacent pixels causing image accuracy to deteriorate
Solution Approach 1:
The patent introduces isolation structures (isolation trenches filled with dielectric material or isolation layers) that segment the common hole layer into electrically isolated regions beneath adjacent pixels. This segmentation prevents lateral leakage currents from flowing between pixels while maintaining the manufacturing simplicity of using a common hole layer structure.
Solution Approach 2:
The patent employs dielectric material filled in isolation trenches or isolation layers as intermediary structures between adjacent pixels. These intermediary structures act as electrical barriers that block lateral current flow in the hole layer, preventing leakage between pixels while allowing the common hole layer to function uniformly across the display.
2Reliability
If doping levels in the hole layer are increased to improve charge transport, then electrical conductivity is improved, but lateral leakage currents increase causing pixels to turn on inadvertently
Solution Approach 1:
By segmenting the hole layer through isolation structures, the patent allows higher doping levels to be used within each pixel region to improve vertical charge transport, while the segmentation prevents the resulting high conductivity from causing lateral leakage between adjacent pixels.
Solution Approach 2:
The dielectric intermediary structures block lateral current flow, enabling the hole layer to maintain high doping levels for improved electrical conductivity and charge transport efficiency without generating harmful lateral leakage currents between pixels.
3Productivity
If blanket films are used to cover the entire display, then manufacturing process is simplified and productivity is improved, but lateral leakage paths are created between adjacent diodes
Solution Approach 1:
The patent maintains the productivity advantage of blanket film deposition for the common hole layer, then applies isolation structures that segment the deposited material into electrically isolated regions. This approach preserves manufacturing efficiency while eliminating lateral leakage paths between adjacent diodes.
Solution Approach 2:
The isolation structures with dielectric material act as intermediary barriers that block lateral leakage paths created by blanket films, allowing the manufacturing process to remain simple and productive while preventing harmful current leakage between pixels.
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
This configuration effectively reduces lateral leakage currents, ensuring accurate and efficient operation of organic light-emitting diode displays by isolating each pixel and preventing interference between adjacent diodes.
Implementation Method 1
The bias path may be maintained at a voltage less than the ground voltage
Data Source
AI summary
A display may have an array of pixels. Each pixel may have a light-emitting diode that emits light under control of a drive transistor. The organic light-emitting diodes may have a common cathode layer, a common electron layer, individual red, green, and blue emissive layers, a common hole layer, and individual anodes. The hole layer may have a hole injection layer stacked with a hole transport layer. Pixel circuits for controlling the diodes may be formed from a layer of thin-film transistor circuitry on a substrate. A planarization layer may cover the thin-film transistor layer. Lateral leakage current between adjacent diodes can be blocked by shorting the common hole layer to a metal line such as a bias electrode that is separate from the anodes. The metal line may be laterally interposed between adjacent pixels and may be formed on the planarization layer or embedded within the planarization layer.