Amoled N-Type TFT Inverted Structure for Image Sticking
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Solution Overview
Problem
Inverted OLEDs face challenges such as oxidation of the cathode layer and high operational voltage, leading to potential damage and reduced lifespan in display panels, along with image sticking defects in active-matrix organic light-emitting diode (AMOLED) displays.
Innovation Solution
A method of fabricating an organic light-emitting diode structure using a substrate with a switching structure comprising a thin-film transistor and a planarization layer, where the organic active layer is formed with an electron transport layer, hole transport layer, and emissive layer, and the cathode is electrically connected to the drain terminal of the transistor, minimizing image sticking and reducing operational voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If inverted OLED structure is used, then cathode is disposed first on substrate, but operational voltage becomes relatively high
Solution Approach 1:
The patent inverts the conventional OLED structure by placing the cathode layer first on the substrate, followed by the organic active layer, then the anode. This inversion allows the cathode to be deposited before the organic layers, simplifying the manufacturing process. The inverted structure is explicitly described in the background section and forms the basis of the invention.
Solution Approach 2:
The patent modifies the operational parameters of the inverted OLED by adjusting the thickness and material composition of the organic active layer and electrode layers. These parameter changes optimize the electrical characteristics to reduce the high operational voltage issue inherent in inverted OLED structures while maintaining the manufacturing advantages.
2Ease of manufacture
If inverted OLED structure is used, then cathode is disposed first on substrate, but cathode layer is subject to oxidation and anode sputtering process can seriously damage underlying organic active layer
Solution Approach 1:
The patent applies preliminary protective actions by introducing barrier layers and optimizing the deposition sequence. The cathode is deposited first with protective measures in place, and the organic active layer is deposited subsequently under controlled conditions to prevent oxidation. The anode sputtering process is carefully controlled to avoid damaging the underlying organic layers.
Solution Approach 2:
The patent introduces intermediary protective layers between the electrodes and organic active layer. These intermediary layers serve as barriers against oxidation and sputtering damage, allowing the inverted structure to be manufactured without the harmful effects mentioned. The protective layers mediate between the deposition processes and the sensitive organic material.
3Ease of operation
If conventional pixel circuit is used, then image display can be achieved, but image sticking defect occurs
Solution Approach 1:
The patent modifies the pixel circuit parameters by changing the transistor type from p-type to n-type. This parameter change in the semiconductor material fundamentally alters the electrical characteristics of the pixel circuit, eliminating the image sticking defect while maintaining the image display function. The n-type TFT is explicitly described as the solution to the image sticking problem.
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 minimizes image sticking and reduces operational voltage, enhancing the lifespan and performance of OLEDs in display panels by ensuring uniform layer thickness and brightness, while protecting the pixel structure from damage.
Implementation Method 1
a thin-film transistor having a source terminal, a gate terminal and a drain terminal
Implementation Method 2
an organic light-emitting diode typically comprises a cathode layer, an electron transport layer (ETL), an emissive layer (EML), a hole transport layer (HTL), a hole injection layer (HIL) and an anode layer
Data Source
Figure 1a~1b
Figure 2a~2b
Figure 3~4
AI summary
A stratified organic light-emitting diode structure includes a thin-film transistor (40) and an organic light-emitting diode (OLED) (60). The OLED (60) is fabricated on a planarization layer (50) that has a top surface substantially parallel to the substrate, and the layers in the organic light-emitting diode (OLED) (60) are substantially parallel to each other. The major part of each OLED layer has a uniform thickness so that the OLED produces a uniform brightness. The planarization layer (50) covers the thin-film transistor entirely and the planarization layer (50) on top of the thin-film transistor is also covered by an insulation layer (52). In order to electrically connect the top electrode of the OLED (60) to the drain terminal (36) of the thin-film transistor (40), an opening (150) is made through both the top insulating layer (52) and the planarization layer (50) to expose part of the drain terminal (36). Spacers (71, 72) with uniform height are fabricated on the top insulating layer (52) to protect the pixel structure.