Parallel-Transistor Pixel Driving Circuit for Low-Brightness Uniformity
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Solution Overview
Problem
Existing display panels suffer from color unevenness at low brightness due to large leakage currents and uneven electrical properties of transistors, primarily caused by low temperature polysilicon technology limitations.
Innovation Solution
The display panel incorporates a pixel driving circuit with driving transistors comprising a first transistor and a second transistor connected in parallel, where the absolute value of the threshold voltage of the first transistor is greater than that of the second transistor, and the carrier mobility of the first transistor is higher. The active layer of the first transistor is made of silicon semiconductor, while the second transistor's active layer is made of oxide semiconductor, ensuring the second transistor turns on earlier, thereby controlling the driving current to mitigate color unevenness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If low temperature polysilicon technology is used for pixel driving circuits, then manufacturing process is simplified, but leakage current increases and electrical properties become uneven
Solution Approach 1:
The driving transistor is segmented into two parallel transistors (first and second transistors) with different active layer materials. This segmentation allows each transistor to contribute differently to the overall current, with the oxide semiconductor transistor providing low leakage current and the silicon semiconductor transistor providing higher current capability, thus resolving the contradiction between ease of manufacture and reliability.
Solution Approach 2:
The invention uses composite materials by combining two different semiconductor materials (oxide semiconductor and silicon semiconductor) in parallel within the same pixel driving circuit. This composite structure leverages the low leakage current特性 of oxide semiconductors while maintaining the high current capability of silicon semiconductors, solving the reliability issues of pure low temperature polysilicon technology.
2Reliability
If transistor leakage current is reduced, then color uniformity improves, but driving current control becomes more difficult
Solution Approach 1:
Different regions of the pixel driving circuit use transistors with locally optimized properties: the oxide semiconductor transistor provides low leakage current for stable voltage holding and color uniformity, while the silicon semiconductor transistor provides high current capability for adequate driving current. This local quality differentiation resolves the contradiction between color uniformity and driving current control.
3Reliability
If oxide semiconductor transistor is used, then leakage current decreases, but carrier mobility is lower
Solution Approach 1:
The invention merges two transistor types with complementary characteristics into a parallel configuration. The oxide semiconductor transistor contributes low leakage current, while the silicon semiconductor transistor contributes high carrier mobility. Together, they provide both reliability and speed, resolving the contradiction between low leakage current and high carrier mobility.
Data Source
AI summary
A display panel, a pixel driving circuit, and a display device are provided. Driving transistors include a first transistor and a second transistor connected in parallel. An absolute value of a threshold voltage of the first transistor is greater than an absolute value of a threshold voltage of the second transistor. A carrier mobility of the first transistor is greater than a carrier mobility of the second transistor. A driving current is affected by characteristics of the second transistor and an increase speed is slowed down, which improves a problem of color unevenness of the display panel at low brightness.