OLED Subpixel Carrier Leak Suppression via Edge-Defined Layers
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Solution Overview
Problem
In OLED display devices, unintended light-emission from red and green subpixels occurs when blue subpixels are driven, causing degradation of color purity and abnormal display in lower gradation due to carrier leak through the carrier supply layer, especially noticeable at closer subpixel distances.
Innovation Solution
The OLED display device incorporates a lower carrier supply layer that covers the entire surface of the lower electrode and has an edge on the top surface of the pixel defining layer, with the organic light-emitting layer covering the entire surface including the edge of the carrier supply layer, reducing or eliminating the leak path between adjacent subpixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the subpixel distance is reduced to increase display resolution, then the display density is improved, but carrier leak between adjacent subpixels increases causing unintended light-emission
Solution Approach 1:
The patent divides the carrier supply function into separate layers for each subpixel. The lower carrier supply layer is formed in correspondence with each lower electrode, creating isolated carrier supply paths that prevent carrier leak between adjacent subpixels while maintaining high display resolution
Solution Approach 2:
The patent applies different structural configurations to different regions. The lower carrier supply layer is selectively formed only in regions where lower electrodes are present, with its edge positioned on the top surface of the pixel defining layer. This localized structure provides carrier supply where needed while preventing carrier migration to adjacent subpixels
2Productivity
If the lower carrier supply layer covers the entire lower electrode surface, then carrier supply efficiency is improved, but the edge of the carrier supply layer may expose and create leak paths
Solution Approach 1:
The patent positions the edge of the lower carrier supply layer on the top surface of the pixel defining layer, utilizing the vertical dimension to create an overlapping structure. The organic light-emitting layer is formed to cover this edge region, and the upper carrier supply layer is positioned above, creating a multi-layer barrier that prevents carrier leak while maintaining efficient carrier supply to the light-emitting region
3Reliability
If the organic light-emitting layer covers the entire carrier supply layer including edges, then carrier leak is suppressed, but manufacturing complexity increases
Solution Approach 1:
The patent combines the coverage function into the standard organic light-emitting layer formation process. The organic light-emitting layer is formed to inherently cover the entire lower carrier supply layer including its edges, integrating the leak prevention function with the light-emitting function rather than adding separate structural elements
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 suppresses carrier leak between subpixels of different colors, preventing unintended light-emission and improving the purity and accuracy of displayed colors, especially in low gradation displays.
Implementation Method 1
The OLED element is a light-emitting element driven by an electric current
Implementation Method 2
supply carriers from the lower electrode to the organic light-emitting layer
Data Source
AI summary
Each of subpixels includes: an upper electrode; a lower electrode; an organic light-emitting layer sandwiched between the upper electrode and the lower electrode; and a lower carrier supply layer sandwiched between the lower electrode and the organic light-emitting layer. The lower carrier supply layer is configured to: make contact with the lower electrode and the organic light-emitting layer, respectively; supply carriers from the lower electrode to the organic light-emitting layer; cover the lower electrode entirely in an opening of the pixel defining layer; and have an edge at a top surface of the pixel defining layer surrounding the lower electrode. The organic light-emitting layer covers an entire surface of the lower carrier supply layer including the edge of the lower carrier supply layer.