Light-Emitting Device With Mixed TFT Structures
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Solution Overview
Problem
Current light-emitting devices with organic compounds face challenges in achieving high-speed operation and reliable switching characteristics for thin film transistors, particularly in high-definition displays where multiple circuits are integrated over a single substrate, requiring distinct transistor structures for pixel and driver circuits.
Innovation Solution
A light-emitting device is designed with a pixel thin film transistor having an inverted coplanar structure and a driver circuit thin film transistor with a channel-etched structure, both utilizing oxide semiconductor layers, where the driver circuit transistor includes a high-resistance drain region and source region to enhance switching performance, and the manufacturing method involves specific heat treatment and material selection to optimize electrical characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single type of thin film transistor structure is used for both pixel portion and driver circuit, then device complexity is reduced, but switching characteristics and operation speed cannot be optimized for different circuit requirements
Solution Approach 1:
The patent applies different transistor structures to different functional regions: inverted coplanar TFTs for pixel portions requiring excellent switching characteristics, and channel-etched TFTs for driver circuits requiring high operation speed. This local differentiation allows each region to have optimized performance for its specific function while maintaining overall device integration.
2Productivity
If high-definition display is implemented with multiple circuits over one substrate, then integration density is improved, but writing time increases and operation speed decreases
Solution Approach 1:
The patent implements local optimization by using channel-etched TFTs specifically in driver circuit regions where high operation speed is critical for handling increased circuit complexity in high-definition displays. This allows the driver circuits to operate at high speeds even when multiple circuits are integrated over one substrate.
3Ease of manufacture
If oxide semiconductor layers are used in both pixel and driver circuit transistors, then manufacturing consistency is improved, but electrical characteristics cannot be differentiated for different circuit functions
Solution Approach 1:
The patent maintains manufacturing consistency by using oxide semiconductor layers throughout, but achieves differentiated electrical characteristics through local structural variations: inverted coplanar structure for pixel TFTs provides excellent switching characteristics, while channel-etched structure for driver TFTs provides high operation speed. This combines ease of manufacture with functional reliability.
Data Source
AI summary
It is an object to provide a light-emitting device in which plural kinds of circuits are formed over one substrate and plural kinds of thin film transistors corresponding to characteristics of the plural kinds of circuits are provided. An inverted coplanar thin film transistor in which an oxide semiconductor layer overlaps with a source electrode layer and a drain electrode layer is used for a pixel, and a channel-etched thin film transistor is used for a driver circuit. A color filter layer is provided between the pixel thin film transistor and a light-emitting element which is electrically connected to the pixel thin film transistor so as to overlap with the light-emitting element.