Light Shielding Layer for X-ray Detection Leakage Current
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Solution Overview
Problem
Current X-ray detection technologies, such as XRD sensors, suffer from poor imaging accuracy due to leakage currents generated by light-sensitive thin film transistors, which are not effectively shielded, leading to misjudgment in imaging processes.
Innovation Solution
A photoelectric conversion array substrate with a thin film transistor and photodetection unit is designed, where a first light shielding layer is positioned directly over the source and drain electrodes of the thin film transistor, and a second light shielding layer is integrated with the signal line, reducing the distance between the shielding layer and the transistor to enhance light shielding and minimize leakage currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the thin film transistor is made light-sensitive to enable photodetection function, then the photodetection capability is improved, but leakage current increases causing imaging inaccuracy
Solution Approach 1:
The patent divides the device into functionally independent regions: a photodetection region with light-sensitive thin film transistor and a control region with light-shielded thin film transistor. The light shielding layer segments the optical path, allowing only the photodetection region to receive light while blocking light from reaching the control region, thereby preventing leakage current generation in the control transistor.
Solution Approach 2:
A light shielding layer is introduced as an intermediary element between the light source and the control thin film transistor. This intermediary blocks harmful light from reaching the control transistor, preventing it from generating leakage current, while allowing the photodetection transistor to maintain its light-sensitive functionality.
2Object-generated harmful factors
If a light shielding layer is added to block light from the thin film transistor, then leakage current is reduced, but the device structure becomes more complex
Solution Approach 1:
The light shielding layer is merged with existing device layers, specifically integrating it into the pixel electrode structure or as part of the encapsulation layers. This merging approach adds the necessary light shielding function without significantly increasing overall device complexity, as the shielding layer shares space and fabrication processes with other device components.
Solution Approach 2:
The light shielding layer is applied locally only where needed - specifically over the control thin film transistor and signal transmission regions - rather than covering the entire device. This localized application maintains the light-sensitive properties of the photodetection transistor while providing shielding only where leakage current would be problematic, thus minimizing added complexity.
3Object-generated harmful factors
If the distance between the light shielding layer and the thin film transistor is reduced to improve shielding effect, then light shielding performance is enhanced, but manufacturing precision requirements increase
Solution Approach 1:
Instead of relying solely on vertical distance for light shielding, the patent utilizes horizontal dimension strategies - the light shielding layer is positioned laterally adjacent to the control transistor with optimized lateral spacing. This dimensional approach provides effective light blocking while maintaining larger vertical distances that are easier to manufacture with standard precision tolerances.
Solution Approach 2:
The light shielding layer is designed and positioned in advance during the fabrication process, with its lateral extent and position pre-calculated to provide adequate shielding at manufacturable distances. This preliminary design approach accounts for manufacturing tolerances and ensures effective light blocking without requiring ultra-precise alignment that would be difficult to achieve in production.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The improved light shielding effectively reduces leakage currents, enhancing the imaging accuracy of the photoelectric detection unit and preventing misjudgment during X-ray imaging.
Implementation Method 1
a first light shielding layer is disposed on the first protective layer, an orthographic projection of the first light shielding layer on the base substrate covers at least an orthographic projection of the active layer on the base substrate
Implementation Method 2
the photodetection unit includes a signal output electrode located on the base substrate, a photosensitive layer located on the signal output electrode, and a transparent electrode located on the photosensitive layer
Data Source
AI summary
The present disclosure provides a photoelectric conversion array substrate and a photoelectric conversion device, and the photoelectric conversion array substrate includes: a base substrate; a thin film transistor located on the base substrate and including a gate, a gate insulating layer disposed on the gate, an active layer disposed on the gate insulating layer, and a source electrode and a drain electrode located on the active layer; a photodetection unit located on the base substrate and including a signal output electrode, a photosensitive layer and a transparent electrode that are located on the base substrate, the signal output electrode electrically connected to the drain electrode, wherein an orthographic projection of the transparent electrode on the base substrate is located within an orthographic projection of the photosensitive layer on the base substrate; a first protective layer covering the source electrode and the drain electrode.