Bottom-Emitting OLED With OTFT On Planarization Film
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Solution Overview
Problem
Conventional active matrix organic light emitting devices have a low aperture ratio and are prone to degradation from external air due to their structure, which can lead to contamination and OTFT degradation during the OLED formation process.
Innovation Solution
A bottom-surface emitting organic light emitting device is designed with an OLED on the upper surface of a transparent substrate and a pixel circuit using an OTFT on a planarization film, allowing for high aperture ratio and protection from air degradation by forming the OLED before the OTFT, ensuring the OTFT is not exposed to high process temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the OLED structure is placed adjacent to the TFT structure on the substrate (conventional AM type), then the device is simple to manufacture, but the aperture ratio is low
Solution Approach 1:
The patent merges the TFT structure and OLED structure by forming the TFT on top of the OLED structure. The substrate serves as a common base for both structures, eliminating the need for separate adjacent placements. This integration allows the light emission region to occupy most of the pixel area, achieving high aperture ratio while maintaining manufacturing simplicity through sequential layer formation.
2Area of stationary object
If the OLED structure is placed close to external air (top-surface emitting), then the aperture ratio is high, but the device is prone to contamination from moisture, water vapor, and oxygen
Solution Approach 1:
The patent changes the spatial arrangement from top-surface emitting to bottom-surface emitting by inverting the OLED structure. The substrate is positioned at the bottom of the OLED stack rather than the top, allowing light to emit from the bottom surface. This dimensional change enables the OLED to be protected from air exposure while maintaining high aperture ratio, as the substrate acts as a barrier against moisture, water vapor, and oxygen.
3Object-affected harmful factors
If the OTFT is formed after the OLED (to protect OLED from air), then the OLED is protected from contamination, but the OTFT may be degraded during the OLED formation process due to high temperature
Solution Approach 1:
The patent applies preliminary action by forming the OLED structure first on the substrate, then forming the TFT structure on top of it. This sequence allows the OLED to be protected from air contamination by the subsequent TFT and protection layers. Although the OLED formation process involves high temperatures, the patent manages this by carefully controlling the process parameters and selecting materials that can withstand the thermal conditions, thereby preventing OTFT degradation while achieving protection from air contamination.
4Object-affected harmful factors
If a thick protection film is provided to protect the OLED from air, then the OLED is protected from degradation, but the device thickness and overall size increase
Solution Approach 1:
The patent eliminates the need for thick protection films by inverting the OLED structure to bottom-surface emitting. The substrate itself serves as the primary protection barrier against air, moisture, and oxygen. This dimensional change allows for a thinner overall device structure while maintaining effective protection, as the substrate provides inherent barrier properties without adding significant thickness.
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 solution achieves a high aperture ratio and protects the OLED from air contamination, while preventing OTFT degradation during manufacturing by forming the OLED on a substrate before the OTFT, resulting in a more stable and efficient organic light emitting device.
Implementation Method 1
An organic light emitting diode ("OLED") is a light emitting device that generates light using an organic electroluminescence phenomenon, where light having a particular wavelength is generated by energy of excitons formed by recombining electrons injected from a cathode and holes injected from an anode
Data Source
AI summary
A bottom-surface emitting organic light emitting device and a method of manufacturing the organic light emitting device includes providing a transparent substrate, an organic light emitting diode (“OLED”) that includes a transparent electrode, an organic light emitting layer, and a pixel electrode sequentially stacked on an upper surface of the transparent substrate, a planarization film covering the OLED, and a pixel circuit that drives the OLED using an organic thin film transistor (“OTFT”) located on the planarization film.