OLED P-Doping Layer for Contrast Ratio Improvement
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Solution Overview
Problem
Organic light emitting diode displays face issues with increased black luminance and deteriorated contrast ratio due to uneven driving voltages and efficiencies across red, green, and blue light-emitting layers, as current tends to concentrate in pixels with lower resistance, leading to higher emission efficiency but reduced contrast.
Innovation Solution
Incorporating a p-doping layer between the first electrode and the light-emitting layer, specifically in red and blue pixels, to control relative driving voltage and efficiency, using materials like hexanitril hexaazatriphenylene, trifluoro-tetracyanoquinodimethane, or metal oxides, to divert current and reduce black luminance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If current is concentrated in pixels with lower resistance to achieve high emission efficiency, then luminance is increased, but contrast ratio is deteriorated due to increased black luminance
Solution Approach 1:
The patent applies different doping conditions to different color pixels (red, green, blue) to create local variations in electrical characteristics. Specifically, red pixels receive a higher doping concentration or additional doping layers compared to green and blue pixels, thereby locally adjusting the hole injection efficiency to balance the overall current distribution across all sub-pixels.
2Use of energy by moving object
If materials with high charge mobility are used in hole injection layer and hole transport layer, then power consumption is reduced and efficiency is increased, but uneven driving voltage across red, green, and blue pixels causes current concentration and black luminance increase
Solution Approach 1:
The patent introduces localized doping adjustments in the hole injection layer or additional doping layers between the hole injection layer and the emitting layer. Red pixels are doped at a higher concentration or receive additional doping treatment compared to green and blue pixels, creating local differences in charge mobility that compensate for the inherent voltage differences and achieve uniform current distribution.
Solution Approach 2:
The patent changes the doping concentration parameter locally across different color pixels. By increasing the doping concentration in red pixels relative to green and blue pixels, the hole injection efficiency is adjusted to balance the driving voltages. This parameter change allows the use of high charge mobility materials while maintaining voltage uniformity across all sub-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
The p-doping layer effectively lowers the driving voltage of red pixels, dispersing leakage current and reducing black luminance, thereby improving the contrast ratio by optimizing the relative efficiencies and voltages across different color pixels.
Implementation Method 1
a p-doping layer between the first electrode and the light-emitting layer
Data Source
AI summary
An organic light emitting diode display including a substrate, a first electrode on the substrate, a light-emitting layer on the first electrode, a second electrode on the light-emitting layer, and a p-doping layer between the first electrode and the light-emitting layer.