OLED Subpixel Layout for Leakage Current and Color Purity
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Solution Overview
Problem
Display apparatuses face issues with leakage current and luminance degradation due to shared organic layers between light emitting diodes, leading to color mixture and reduced display quality.
Innovation Solution
Incorporating a conductive layer between sub pixels with different turn-on voltages, where the conductive layer is closer to the sub pixel with a lower turn-on voltage, to minimize leakage current and maintain luminance by acting as an auxiliary light emitting diode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If light emitting diodes share a common organic layer and cathode to reduce device complexity, then manufacturing cost and structure are simplified, but leakage current occurs between adjacent sub pixels with different turn-on voltages
Solution Approach 1:
An insulating layer is introduced between adjacent light emitting diodes sharing a common organic layer and cathode. This insulating layer acts as a mediator that prevents direct current leakage between adjacent sub pixels with different turn-on voltages, while still allowing the beneficial shared structure to remain in place for simplified manufacturing.
2Reliability
If a conductive layer is added between sub pixels to suppress leakage current, then reliability improves, but device complexity and manufacturing steps increase
Solution Approach 1:
The patent segments the device into distinct functional regions by introducing both insulating and conductive layers at specific locations. The insulating layer segments the current paths to prevent leakage, while the conductive layer segments and redirects leakage current to useful emission regions, creating a more complex but functional structure.
Solution Approach 2:
The conductive layer serves as an intermediary element that captures leakage current between sub pixels and redirects it through the emission layer to produce useful light. This mediator transforms harmful leakage current into beneficial emission, adding functional complexity that justifies the additional structural elements.
3Reliability
If the conductive layer is positioned closer to the sub pixel with lower turn-on voltage to minimize leakage, then leakage current suppression improves, but luminance uniformity may be affected
Solution Approach 1:
The patent applies local quality by positioning the conductive layer asymmetrically closer to the sub pixel with lower turn-on voltage. This localized placement optimizes leakage suppression at the critical interface while the emission layer extends across both regions to maintain uniform luminance output, creating different functional properties in different spatial locations.
Solution Approach 2:
The structure employs asymmetry in the placement of the conductive layer relative to adjacent sub pixels. Rather than symmetric positioning, the conductive layer is deliberately placed closer to one sub pixel to optimize the suppression of leakage current based on the different turn-on voltage characteristics of adjacent pixels, with the emission layer compensating for luminance uniformity.
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 reduces leakage current and minimizes luminance degradation, enhancing display quality by preventing color mixture and maintaining accurate color representation.
Implementation Method 1
even though the current is leaked from the sub pixel, the emission layer on the conductive layer emits light to minimize the degradation of the luminance of the sub pixel
Data Source
AI summary
According to an aspect of the present disclosure, a display apparatus includes a substrate in which a plurality of sub pixels is defined; a plurality of light emitting diodes which are disposed in the plurality of sub pixels, share a common organic layer and a cathode, and have an emission layer and an anode which are separated, respectively; a conductive layer disposed between the plurality of sub pixels; and a bank which is disposed below the cathode between the plurality of light emitting diodes and exposes the anode and the conductive layer. The plurality of sub pixels include a first sub pixel and a second sub pixel having a turn-on voltage lower than that of the first sub pixel, and the conductive layer is disposed to be closer to the second sub pixel between the first sub pixel and the second sub pixel.