TFT Substrate Height Adjustment Layer for OLED Uniformity
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Solution Overview
Problem
AMOLED displays face defects due to the configuration of TFTs on the lower side, leading to non-uniform light emission and brightness issues caused by height differences in the substrate, which affect the formation and uniformity of the OLED layer.
Innovation Solution
A TFT substrate with a height adjustment layer, made of metal or inorganic materials, is used to minimize height differences, allowing for a planarization layer that ensures a flat surface for the pixel electrode, enabling a uniform thickness of the intermediate layer with an emission layer, thereby improving brightness uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a TFT is disposed on the substrate to control light emission in each sub-pixel, then light emission control is improved, but height differences are created in the substrate areas
Solution Approach 1:
The patent applies preliminary action by forming the height adjustment layer in advance before depositing the OLED layers. This layer is created to compensate for future height variations caused by TFT placement, ensuring that when the OLED layers are added, the entire structure maintains uniform height and enables consistent light emission across all sub-pixels.
2Manufacturing precision
If height adjustment layer is added to minimize height differences, then substrate height uniformity is improved, but device complexity increases
Solution Approach 1:
The height adjustment layer serves multiple functions simultaneously: it acts as a height compensation layer to minimize substrate height differences, provides a planarization surface for subsequent OLED layer deposition, and can function as an additional protective or insulating layer. This multi-functionality reduces the need for separate dedicated layers, thereby limiting the increase in device complexity.
3Shape
If planarization layer is disposed to cover height adjustment layer and TFT, then surface flatness is improved, but manufacturing steps increase
Solution Approach 1:
The patent merges the planarization function with the OLED layer deposition process. The planarization layer is formed as part of the same deposition sequence that creates the emission layer and other OLED components, rather than as a separate intermediate step. This integration reduces the total number of manufacturing steps and maintains productivity while achieving the necessary surface flatness.
Data Source
AI summary
A thin film transistor (TFT) substrate having reduced differences in heights in areas thereof so as to facilitate subsequent processing is disclosed. In one aspect, the TFT substrate includes a substrate having a first area in which a TFT is not disposed and a second area in which a TFT is disposed, a height adjustment layer disposed on the substrate in an area corresponding to at least a part of the first area. The TFT substrate also includes a TFT disposed on the substrate in an area corresponding to the second area.