Conductive Layer Mediator for OLED TFT Mobility and Uniformity
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Solution Overview
Problem
Conventional organic light-emitting display devices face challenges with low mobility in amorphous silicon TFTs and non-uniform threshold voltage in poly-silicon TFTs, along with high equipment costs and complexity in manufacturing large-sized substrates due to the need for high-priced laser heat treatment processes.
Innovation Solution
The organic light-emitting display device incorporates a substrate with a thin film transistor, a conductive layer overlapping the semiconductor layer, an insulating layer, a passivation layer, a pixel electrode, an emission layer, and an opposite electrode, where the conductive layer is connected to the opposite electrode through a hole in the insulating layer, and auxiliary electrodes are used to reduce resistance and brightness deviations, while a method involving laser irradiation and intermediate layers simplifies the manufacturing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If amorphous silicon is used for the active layer, then manufacturing cost is reduced and manufacturing process is simplified, but carrier mobility is low
Solution Approach 1:
A conductive layer is introduced as an intermediary component between the substrate and the semiconductor layer. This conductive layer has high carrier mobility and serves as a mediator to improve the overall electrical performance of the device while allowing the use of amorphous silicon in the semiconductor layer, thus maintaining manufacturing simplicity.
2Speed
If poly-silicon is used for the active layer, then carrier mobility is improved, but threshold voltage becomes non-uniform requiring compensation circuits
Solution Approach 1:
The conductive layer acts as an intermediary that provides a stable electrical reference and uniform charge distribution, compensating for the threshold voltage non-uniformity inherent in poly-silicon based TFTs without requiring additional compensation circuits.
3Speed
If conventional TFT manufacturing method using LTPS is used, then carrier mobility is improved, but equipment investment and management costs are high
Solution Approach 1:
The device structure is segmented into distinct functional layers: a conductive layer for high mobility charge transport, an insulating layer for electrical isolation, and an amorphous silicon semiconductor layer for switching functionality. This segmentation allows each layer to be optimized independently using standard manufacturing processes, avoiding the need for expensive LTPS equipment.
4Reliability
If conventional TFT manufacturing method is used, then TFT performance is improved, but application to large-sized substrates becomes difficult
Solution Approach 1:
The invention changes the material parameters and structural configuration of the TFT, using amorphous silicon with a conductive layer instead of LTPS. This parameter change enables the manufacturing process to be scaled to large-sized substrates while maintaining acceptable TFT performance, as the process does not require high-temperature laser annealing that is difficult to scale.
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 configuration enhances the mobility of carriers, maintains constant brightness, reduces resistance and IR drops, and simplifies the manufacturing process, making it suitable for large-sized substrates with improved light emission stability.
Implementation Method 1
a conductive layer between the substrate and the semiconductor layer of the thin film transistor
Implementation Method 2
an insulating layer between the conductive layer and the thin film transistor
Implementation Method 3
a method involving laser irradiation and intermediate layers simplifies the manufacturing process
Data Source
AI summary
An organic light-emitting display device includes: a substrate; a thin film transistor over the substrate, the thin film transistor including a semiconductor layer and a gate electrode overlapping the semiconductor layer; a conductive layer between the substrate and the semiconductor layer of the thin film transistor; an insulating layer between the conductive layer and the thin film transistor; a passivation layer covering the thin film transistor; a pixel electrode over the passivation layer, the pixel electrode being electrically connected to the thin film transistor via a contact hole defined in the passivation layer; an emission layer over the pixel electrode; and an opposite electrode over the emission layer, the opposite electrode being electrically connected to the conductive layer.