OLED Pixel Circuit Using Oxide and LTPS Transistors
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Solution Overview
Problem
Existing OLED devices face challenges in achieving high aperture ratio and high resolution due to the large area required for thin-film transistors and capacitors, limiting the miniaturization of pixels and the manufacturing of high-transparent panels when only one type of thin-film transistor is used.
Innovation Solution
The OLED device employs both oxide semiconductor and LTPS thin-film transistors, with adjacent pixels sharing a gate line, allowing for a composite structure that reduces the area occupied by storage capacitors and enables high-resolution and high-transparency panels by forming multi-layer capacitors without increasing capacitor area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If only one type of thin-film transistor is used, then the device structure is simple, but the area occupied by storage capacitors increases, reducing aperture ratio
Solution Approach 1:
The patent applies different transistor types (oxide semiconductor and LTPS) to different functional requirements within the pixel circuit. Oxide semiconductor transistors are used where low leakage current is critical for storage capacitor performance, while LTPS transistors are used where high mobility is needed for switching performance. This local differentiation optimizes each component's performance without uniformly increasing complexity across the entire device.
Solution Approach 2:
The patent employs a composite approach by integrating two different thin-film transistor technologies (oxide semiconductor and LTPS) within the same pixel circuit. This composite structure allows the storage capacitor to benefit from the low leakage characteristics of oxide semiconductor transistors while the switching function benefits from the high mobility of LTPS transistors, thereby reducing the required capacitor area without compromising overall circuit performance.
2Manufacturing precision
If transistor size is reduced to achieve high resolution, then pixel density increases, but transistor performance deteriorates
Solution Approach 1:
The patent changes the material parameters of the transistor active layers by using oxide semiconductor and LTPS materials, which inherently provide superior electrical characteristics (lower leakage current and higher mobility) compared to conventional amorphous silicon. This material parameter change allows transistors to maintain high performance even when scaled down to smaller dimensions required for high-resolution displays.
3Area of stationary object
If aperture ratio is increased for high transparency, then active emission area increases, but circuit element area must be reduced
Solution Approach 1:
The patent optimizes different regions of the pixel circuit with specialized transistor types matched to their functional requirements. Storage capacitors utilize oxide semiconductor transistors for minimal leakage, allowing smaller capacitor dimensions, while switching transistors use LTPS for high-speed operation. This regional optimization reduces the total circuit element area, thereby increasing the emission area and aperture ratio without compromising circuit functionality.
Data Source
AI summary
Disclosed herein is an OLED (Organic Light Emitting Display) device. A switching thin-film transistor configured to be an oxide semiconductor thin-film transistor is disposed in a first pixel. A second pixel is adjacent to the first pixel in the direction in which data lines are extended. A switching thin-film transistor configured to be an LTPS (Low Temperature Poly-Silicon) thin-film transistor is disposed in the second pixel. The switching thin-film transistor of the first pixel and the switching thin-film transistor of the second pixel are connected to the same gate line. A pixel and another pixel adjacent to the pixel connected to a gate line in common, so that it is possible to provide an OLED device with high aperture ratio and high resolution.