Blue Common Light Emitting Layer for OLED Color Purity
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Solution Overview
Problem
Existing organic light emitting displays face issues with color purity and efficiency due to the deterioration of the blue light emitting layer when formed by a general deposition process, particularly when it contacts a hole transport layer formed by a solution process, leading to surface non-uniformity and reduced lifespan.
Innovation Solution
The introduction of a blue common light emitting layer formed over the entire surface of sub-pixels, with a buffer layer or hole transport layer containing a blue host and dopant, which prevents interfacial instability and improves hole and electron injection capacities, allowing for the emission of blue light without affecting red and green light emission, thereby enhancing color purity and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a blue light emitting layer is formed commonly in red, green and blue sub-pixels by deposition, then the fabrication process is simplified, but color purity of red and green light is deteriorated due to blue spectrum emission
Solution Approach 1:
The patent applies local quality by creating different light emitting layer configurations for different sub-pixels. Specifically, the red and green sub-pixels have their respective light emitting layers formed only in those specific regions, while the blue light emitting layer is formed commonly across all sub-pixels. This spatial differentiation ensures that blue light is emitted only in blue sub-pixels, maintaining color purity while allowing process simplification through common layer formation.
2Productivity
If a blue light emitting layer formed by deposition contacts a hole transport layer formed by solution process, then the fabrication process is continuous, but surface non-uniformity occurs at the interface leading to reduced lifespan and efficiency
Solution Approach 1:
The patent introduces an intermediary layer between the blue light emitting layer (formed by deposition) and the hole transport layer (formed by solution process). This intermediary layer acts as a buffer that reconciles the interface between the two differently-formed layers, ensuring surface uniformity and preventing the deterioration of the blue light emitting layer while maintaining continuous fabrication process.
3Reliability
If a blue light emitting layer is formed in red and green sub-pixels, then hole and electron injection is improved, but blue light emission during red and green light emission reduces color purity
Solution Approach 1:
The patent applies segmentation by dividing the light emitting layer formation into sub-pixel-specific segments. The blue light emitting layer is segmented to be formed only in blue sub-pixels, while red and green light emitting layers are formed only in their respective sub-pixels. This segmentation allows each sub-pixel to have optimized charge injection characteristics without cross-contamination of light emission, maintaining both reliability and color purity.
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 improves the luminance and color purity of red and green light emitting layers by inhibiting blue light emission during red and green light emission, extends the lifespan of the blue light emitting layer, and simplifies the fabrication process by eliminating the need for a shadow mask during deposition.
Implementation Method 1
Holes injected from the anode recombine with electrons injected from the cathode in the light emitting layer to form electron-hole pairs, i.e., excitons. Light is emitted by energy generated upon transition of the excitons to a ground state.
Implementation Method 2
a blue common light emitting layer formed in the first to third sub-pixels between the first and second electrodes
Data Source
AI summary
Discussed are an organic light emitting display and a method for fabricating the same to improve color purity and efficiency. The organic light emitting display includes a substrate having first to third sub-pixels, first and second electrodes formed on the substrate, the first and second electrodes facing each other, a red light emitting layer formed in the first sub-pixel between the first and second electrodes, a green light emitting layer formed in the second sub-pixel between the first and second electrodes, and a blue common light emitting layer formed in the first to third sub-pixels between the first and second electrodes, wherein a thin film layer formed between the first electrode and the blue common light emitting layer and contacting the blue common light emitting layer includes a blue host.