OLED Anode Sheet Resistance Gradient for Brightness Uniformity
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Solution Overview
Problem
In OLED display substrates, the nonuniform thickness of the organic functional layer due to ink climbing during ink-jet film deposition leads to brightness uniformity issues, with central regions being brighter and peripheral regions being dimmer, resulting in nonuniform light emission.
Innovation Solution
The solution involves adjusting the sheet resistance of anodes by creating anode structures with varying resistances, such as first, second, and third anodes with different thicknesses and positions, to control the electric current strength and brightness levels across the pixel regions, ensuring uniform light emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If ink-jet film deposition is used to form organic functional layers, then manufacturing flexibility and patternability are improved, but nonuniform thickness distribution occurs causing brightness uniformity deterioration
Solution Approach 1:
The patent applies local quality by creating anodes with spatially varying sheet resistance characteristics. Specifically, the anode structure includes a first anode region with higher sheet resistance and a second anode region with lower sheet resistance, allowing different regions to compensate for the nonuniform organic functional layer thickness. This local differentiation of electrical properties enables uniform current distribution despite thickness variations caused by ink-jet deposition.
2Ease of manufacture
If the organic functional layer thickness varies across the pixel, then manufacturing process simplicity is improved, but light emission uniformity deteriorates
Solution Approach 1:
The patent employs parameter changes by modifying the sheet resistance parameter of the anode across different spatial regions. The anode is designed with a gradient or stepped resistance profile where the sheet resistance value changes from one region to another. This parameter variation compensates for the thickness nonuniformity of the organic functional layer, ensuring uniform current density and light emission without complicating the manufacturing process.
3Device complexity
If uniform anode sheet resistance is used, then device structure simplicity is improved, but current distribution uniformity deteriorates due to thickness variations
Solution Approach 1:
The patent applies segmentation by dividing the anode into multiple functional regions with different sheet resistance characteristics. The anode is segmented into a first anode region and a second anode region, each with tailored electrical properties. This segmentation allows independent optimization of current distribution in different areas, compensating for thickness variations while maintaining overall structural simplicity and manufacturability.
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 approach effectively addresses the nonuniform brightness issue by adjusting anode resistance values, improving light emission uniformity and overall display performance by optimizing electric current distribution across the pixel regions.
Implementation Method 1
the sheet resistance of the portion of the anodes that is proximal to the pixel defining layer is smaller than the sheet resistance of the portion of the anodes that is opposite from the pixel defining layer
Data Source
AI summary
An organic light-emitting diode (OLED) display panel includes: a base substrate; one or more thin-film transistor (TFT) structures provided over the base substrate; a planarization layer provided over the TFT structures; anodes provided on an upper surface of the planarization layer; a pixel defining layer provided over the planarization layer defining a plurality of pixel regions, wherein each anode includes an upper surface being exposed in each of the pixel regions; an organic functional layer provided over the anodes; and a cathode provided over the organic functional layer; wherein a sheet resistance of the portion of the anodes that is proximal to the pixel defining layer is smaller than a sheet resistance of the portion of the anodes that is opposite from the pixel defining layer.