Organic Light Emitting Display Device with Localized Organic Layer Thickness
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Solution Overview
Problem
Conventional organic light emitting display devices face challenges in achieving an appropriate organic layer thickness, leading to high probabilities of dark pixels when the layer is formed thinly or decreased efficiency and lifespan when it is formed thickly, making it difficult to balance these factors.
Innovation Solution
The solution involves individually controlling the combined thickness of the hole injection layer (HIL) and hole transport layer (HTL) for each RGB sub-pixel, ranging from approximately 500 to 700 Å to 2000 to 2400 Å, to optimize the number of dark pixels, efficiency, and lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If the organic layer is formed thinly, then the lifespan of the device is extended, but the probability of dark pixels increases
Solution Approach 1:
The patent applies different thickness values of the organic layer (comprising HIL and HTL) to different pixel regions based on their emission characteristics. Specifically, green pixels with higher emission intensity receive thinner organic layers (500-700 Å) to extend lifespan, while blue pixels with lower emission intensity receive thicker organic layers (2000-2400 Å) to reduce dark pixel probability. This localized differentiation resolves the contradiction by allowing each pixel type to operate at its optimal thickness point.
2Reliability
If the organic layer is formed thickly, then the probability of dark pixels is reduced, but driving electric current increases and efficiency and lifespan decrease
Solution Approach 1:
The patent implements spatially varying organic layer thicknesses matched to the emission characteristics of different pixel types. Green pixels receiving thinner layers (500-700 Å) achieve lower driving current and higher efficiency, while blue pixels receiving thicker layers (2000-2400 Å) achieve adequate dark pixel suppression. This resolves the contradiction by allowing each pixel to operate at its optimal current efficiency point rather than using a uniform thickness that compromises overall performance.
3Ease of manufacture
If a uniform organic layer thickness is used, then the manufacturing process is simplified, but it is difficult to balance dark pixel probability, efficiency, and lifespan
Solution Approach 1:
The patent differentiates organic layer thickness by pixel region (green pixels: 500-700 Å, blue pixels: 2000-2400 Å) to optimize performance. This is achieved through region-specific deposition control during manufacturing, which maintains process simplicity while achieving the performance balance that uniform thickness cannot provide.
Solution Approach 2:
The patent changes the thickness parameter of the organic layer based on pixel emission characteristics. By adjusting this physical parameter differently for green and blue pixels, the patent achieves optimal balance among dark pixel probability, efficiency, and lifespan without complicating the fundamental deposition process.
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 reduces the number of dark pixels and enhances the lifespan and efficiency of the organic light emitting display device by allowing for tailored thickness settings for each color sub-pixel, improving overall display performance.
Implementation Method 1
holes are injected from the pixel electrode into the EML via the HIL and the HTL, and electrons are injected from the counter electrode into the EML via the EIL and the ETL. The holes and electrons injected into the EML are recombined in the EML to create excitons. Light is emitted while the excitons transition from an excited state to a ground state.
Implementation Method 2
In general, a conventional top emitting organic light emitting display device uses a light resonance effect so that it is important to match the thickness of the pixel electrode and the thicknesses of the HIL and HTL disposed between the EML and the pixel electrode with a possible wavelength band.
Data Source
AI summary
An organic light emitting display device and a method of fabricating the same are provided. The device includes: a substrate having a first pixel region, a second pixel region and a third pixel region; a first electrode disposed on the substrate; an organic emission layer disposed on the first electrode; a second electrode disposed on the organic emission layer; and a first organic layer and a second organic layer disposed between the first electrode and the organic emission layer. The first organic layer and the second organic layer have a combined thickness of approximately 500 to 700 Å or approximately 2000 to 2400 Å in the first pixel region, approximately 1600 to 2000 Å in the second pixel region, and approximately 200 to 400 Å in the third pixel region.