Hybrid OLED Pixel Circuit With Top-Gate TFTs for Low Leakage
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Solution Overview
Problem
Thin-film transistor circuitry in displays may exhibit non-uniformity, excessive leakage currents, insufficient drive strengths, poor area efficiency, hysteresis, and other issues if not properly designed and constructed.
Innovation Solution
The implementation of a display pixel structure that includes an organic light-emitting diode (OLED), a semiconducting-oxide top-gate thin-film transistor (drive transistor), a silicon top-gate thin-film transistor (switching transistor), and a storage capacitor coupled to the drive transistor, with specific configurations such as a top-gate design and the use of conductive semiconducting-oxide materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional thin-film transistor circuitry is used in displays, then device complexity is reduced and ease of manufacture is improved, but non-uniformity, excessive leakage currents, insufficient drive strengths, and hysteresis occur
Solution Approach 1:
The transistor circuit is segmented into two distinct transistor types: a first transistor with a semiconducting-oxide semiconductor layer and a second transistor with a silicon-based semiconductor layer. This segmentation allows each transistor type to be optimized for specific functions, with the semiconducting-oxide transistor providing low leakage current and the silicon transistor providing high drive strength, thereby resolving the contradiction between reliability and device complexity.
Solution Approach 2:
Different semiconductor materials are applied locally to different transistors within the same display device. The semiconducting-oxide material is used specifically for transistors requiring low leakage current, while silicon-based material is used for transistors requiring high drive strength. This local quality differentiation enables each transistor to perform optimally for its specific function without requiring complex overall structure.
2Reliability
If conventional thin-film transistor circuitry is used in displays, then area efficiency is improved, but excessive leakage currents and insufficient drive strengths occur
Solution Approach 1:
The display pixel circuit is segmented into specialized transistor units, with semiconducting-oxide transistors handling switching functions requiring low leakage and silicon transistors handling drive functions requiring high current. This functional segmentation achieves high drive strength without proportionally increasing total pixel area, as each segment is optimized for its specific role.
Solution Approach 2:
The display device employs a composite transistor architecture combining semiconducting-oxide semiconductor layers and silicon-based semiconductor layers within the same pixel circuit. This composite approach leverages the complementary strengths of different materials: semiconducting-oxide provides low leakage current for efficient area utilization, while silicon provides high drive strength, together resolving the contradiction between drive strength and area efficiency.
Data Source
AI summary
An electronic device may include a display having an array of display pixels on a substrate. The display pixels may be organic light-emitting diode display pixels, that include hybrid thin-film transistor structures formed using semiconducting-oxide thin-film transistors, silicon thin-film transistors, and capacitor structures. A drive transistor in the display pixel may be a top-gate semiconducting-oxide thin-film transistor and a switching transistor in the display pixel may be a top-gate silicon thin-film transistor. A storage capacitor in the display may include a conductive semiconducting-oxide electrode.