OLED Common Blue Emission Layer and Optical Thickness Auxiliary Layers
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Solution Overview
Problem
Conventional OLED manufacturing processes face challenges such as misalignment of micro-patterns and reduced lifetime of green diodes due to the formation of a blue emission layer as a common layer, which degrades the characteristics of OLEDs, particularly affecting the green diode's performance.
Innovation Solution
An organic light-emitting diode structure is implemented with a first, second, and third sub-pixel, featuring a common blue organic emission layer, accompanied by specific optical thickness auxiliary layers and hole transporting compounds, including cyano group-containing compounds and hole transporting materials, to optimize the optical thickness and hole transport properties, thereby enhancing image quality and longevity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a blue emission layer is formed as a common layer in the lower portion of the emission layer, then the number of patterning processes decreases, but the characteristics of the OLED, particularly the green diode, are degraded and the lifetime is shortened
Solution Approach 1:
The emission layer is segmented into distinct red, green, and blue emission layers with the blue layer positioned in the upper portion rather than as a common lower layer. This segmentation allows each color to have its own dedicated emission region, preventing the degradation and lifetime shortening issues that occur when a common blue layer is used in the lower portion.
Solution Approach 2:
The blue emission layer is repositioned from the lower portion to the upper portion of the emission layer structure, changing its vertical dimension position. This dimensional rearrangement allows the blue layer to function as a common layer while avoiding the harmful effects on green diode characteristics and lifetime that occur when it is positioned in the lower portion.
2Device complexity
If a blue emission layer is formed as a common layer, then manufacturing complexity is reduced, but misalignment of micro-patterns may occur
Solution Approach 1:
By repositioning the blue emission layer to the upper portion of the emission layer structure, the patent changes the vertical dimension arrangement to eliminate misalignment issues. This dimensional change allows the blue layer to be formed as a common layer without causing micro-pattern misalignment, as it no longer interferes with the underlying red and green emission layer patterns.
3Speed
If holes move faster than electrons in each pixel unit, then a hole blocking layer must be formed on the emission layer, but this adds process complexity
Solution Approach 1:
The patent extracts or removes the need for a separate hole blocking layer by positioning the blue emission layer in the upper portion. This configuration inherently manages hole transport without requiring additional hole blocking structures, thereby reducing process complexity while still addressing the faster hole movement issue.
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 results in an OLED with low driving voltage, high image quality, and extended lifetime by adjusting optical thickness and hole transport properties, preventing color mixing and panel defects, and ensuring satisfactory performance across sub-pixels.
Implementation Method 1
The holes and electrons recombine in the EML to generate excitons. When the excitons drop from the excited state to the ground state, light is emitted.
Data Source
AI summary
An organic light-emitting diode (OLED) having first, second and third sub-pixels of different colors includes: a substrate; first and second electrodes; an organic emission layer (OEL) between the electrodes including a first OEL in the first sub-pixel, a second OEL in the second sub-pixel, and a common third OEL in the first, second and third sub-pixels; a hole transport layer (HTL) between the first electrode and OEL; a hole injection layer (HIL) between the first electrode and HTL; an intermediate layer between the HTL and HIL; a first optical thickness auxiliary layer (OTAL) between the first OEL and third OEL in the first sub-pixel and including a first hole transporting compound and a cyano group-containing compound; and a second OTAL including a second hole transporting compound between the third OEL and HTL in the first sub-pixel, and between the second OEL and HTL in the second sub-pixel.