Composite Transistor for Display Panel Node Voltage Stability
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Solution Overview
Problem
The stability of the node voltage and operation state in pixel driving circuits of display panels is unstable due to deviations in the driving current provided to organic light-emitting elements, affecting display performance.
Innovation Solution
Incorporating composite transistors, specifically a series connection of low-temperature polysilicon and oxide transistors, which have a composite active layer, gate electrode, source electrode, and drain electrode, and are electrically connected to a storage capacitor or in an off state during the light-emitting phase, to minimize leakage current and maintain stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional transistors are used in the pixel driving circuit, then the device complexity is low, but the node voltage stability and operation state stability deteriorate due to leakage current affecting the storage capacitor
Solution Approach 1:
The transistor is divided into two separate sub-transistors connected in series: a first sub-transistor (oxide semiconductor transistor) and a second sub-transistor (low-temperature polysilicon transistor). This segmentation allows each sub-transistor to contribute different characteristics - the oxide transistor provides low leakage current while the low-temperature polysilicon transistor provides good stability, thereby improving node voltage stability without requiring a completely new transistor design
Solution Approach 2:
The patent uses composite transistor structures combining different semiconductor materials - oxide semiconductor material for the first sub-transistor and low-temperature polysilicon material for the second sub-transistor. This composite approach leverages the complementary advantages of different materials to achieve both low leakage current and high stability, resolving the contradiction between reliability and device complexity
2Manufacturing precision
If the transistor leakage current is not minimized, then the manufacturing process is simpler, but the storage capacitor potential becomes unstable affecting light-emitting brightness accuracy
Solution Approach 1:
By segmenting the transistor into series-connected sub-transistors with different material compositions, the design achieves precise control over leakage current characteristics. The oxide semiconductor sub-transistor specifically targets leakage reduction, while the low-temperature polysilicon sub-transistor maintains manufacturing compatibility with existing processes, thus improving brightness accuracy without excessive manufacturing complexity
Solution Approach 2:
The patent changes the material parameters and structural parameters of the transistor - using oxide semiconductor material with specific electrical characteristics for the first sub-transistor and low-temperature polysilicon for the second. These parameter changes optimize the leakage current characteristics and stability without requiring complete process retooling, balancing manufacturing precision and ease of manufacture
Data Source
AI summary
A display panel includes a substrate and a plurality of pixel driving circuits disposed on the substrate, and the plurality of pixel driving circuits include a storage capacitor and transistors. The transistors include transistors of a first type and a second type. The transistor of the first type is a composite transistor and includes a first sub-transistor and a second sub-transistor that are connected in series. The first sub-transistor is a low-temperature polysilicon transistor, and the second sub-transistor is an oxide transistor. The transistor of the first type includes a composite active layer, a composite gate electrode, a composite source electrode, and a composite drain electrode. The composite source electrode or the composite drain electrode of the transistor of the first type is electrically connected to the storage capacitor, or the transistor of the first type is in an off state during a light-emitting phase.