Top Emission EL Display Aperture Ratio
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Solution Overview
Problem
Conventional bottom emission type electro-luminescent (EL) devices have a limited light-emitting area due to thin film transistors, leading to reduced aperture ratio and increased power consumption, which shortens the device's lifetime.
Innovation Solution
A top emission type electro-luminescent display device is designed with a substrate having distinct regions for transistors and light-emission, featuring a thin film transistor, interlayer insulator, opaque electrode, opaque layer, and transparent electrode, where the electro-luminescent medium layer is exposed through openings in the opaque layer, allowing light to be emitted upwards, thus increasing the aperture ratio and maintaining brightness without increased power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the number of thin film transistors is increased to improve display functionality, then the aperture ratio is reduced, but power consumption must be increased to maintain brightness
Solution Approach 1:
The patent inverts the conventional bottom emission architecture to a top emission architecture, where the electro-luminescent medium layer is positioned above the opaque electrode rather than below it. This inversion allows light to exit through the transparent electrode on top, enabling the opaque electrode to be positioned lower in the structure where it does not block the light emission path, thereby increasing the aperture ratio while maintaining display functionality
Solution Approach 2:
The patent repositions the electro-luminescent medium layer and light emission path to a different dimensional arrangement by placing the medium layer above the opaque electrode. This dimensional reorganization allows the opaque electrode to be located in a position that does not interfere with light emission, effectively increasing the aperture ratio without compromising display functionality
2Device complexity
If the aperture ratio is reduced to accommodate more thin film transistors, then device complexity is improved, but power consumption increases, reducing device lifetime
Solution Approach 1:
By inverting the emission direction to top emission, the patent allows the opaque electrode to be positioned in the lower structure without blocking light output. This enables a higher aperture ratio that reduces the number of transistors needed, thereby lowering power consumption while maintaining device complexity
Solution Approach 2:
The patent changes the aperture ratio parameter by repositioning the electro-luminescent medium layer and opaque electrode. This parameter change allows for fewer transistors to be required, which directly reduces power consumption and extends device lifetime
3Ease of manufacture
If a bottom emission design is used, then manufacturing simplicity is maintained, but light-emitting area is limited
Solution Approach 1:
The patent inverts the conventional bottom emission design to a top emission design, where the electro-luminescent medium layer is positioned above the opaque electrode. This inversion enables the light-emitting area to be increased without significantly complicating the manufacturing process, as the layer stacking order is reversed but the fabrication steps remain similar
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 top emission design enhances the light-emitting area and reduces power consumption, potentially extending the device's lifetime by maintaining brightness even with increased thin film transistors, and improves display quality by blocking lateral light scattering.
Implementation Method 1
Electro-luminescent (EL) devices, such as organic light-emitting diodes (OLEDs), are active lighting devices using organic materials. When an electrical potential difference is applied between the anode and the cathode, electrons and holes are injected into the EL-medium layer from the cathode and the anode, respectively. The injected electrons and holes are then recombined, releasing energy as light.
Data Source
AI summary
A top emission type electro-luminescent display device comprising a thin film transistor, an opaque electrode, an opaque layer, and an electro-luminescent medium layer. The thin film transistor overlies a substrate and is covered by an interlayer insulator. The opaque electrode and the opaque layer are successively disposed on the interlayer insulator, in which the opaque electrode is electrically connected to the thin film transistor and the opaque layer comprises an opening exposing a portion of the underlying opaque electrode. The electro-luminescent medium layer is disposed over the exposed portion of the opaque electrode. The transparent electrode is disposed on the opaque layer and conformally covers the surfaces of the opening and the electro-luminescent medium layer.