Radiation Image Detector Charge Transport Layer Interface Purity
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Solution Overview
Problem
Radiation image detectors face image quality degradation due to charge traps at the interface between the charge transport layer and X-ray detection layer, caused by impurities like oxygen and chlorine, which affect both short-term and long-term lag characteristics.
Innovation Solution
The radiation image detection apparatus includes a bias electrode, a photoconductive layer, and an active matrix substrate with charge transport layers that minimize oxygen and chlorine density at the interface, using antimony sulfide with specific compositions and an organic polymer layer with electron hole blocking materials to reduce charge traps and improve image lag characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a charge transport layer is introduced between the photoconductive layer and active matrix substrate, then injection of electron holes into the photoconductive layer is prevented and image quality degradation is avoided, but impurities such as oxygen and water may deposit at the interface and cause charge traps that worsen image lag characteristics
Solution Approach 1:
The patent applies local quality by creating a charge transport layer with non-uniform composition - specifically, the antimony sulfide layer has varying sulfur content across its thickness, with higher sulfur content (lower antimony content) at the interface region with the photoconductive layer. This local compositional variation reduces impurity deposition and charge trap formation at the critical interface while maintaining charge transport functionality throughout the layer.
Solution Approach 2:
The patent uses composite materials by combining antimony sulfide with controlled stoichiometry (Sb2-xS3 layer) and incorporating it into a multi-layer structure with the photoconductive layer and active matrix substrate. The composite nature of the charge transport layer, with its specific composition gradient, allows simultaneous achievement of charge transport and impurity rejection functions.
2Manufacturing precision
If the interface between charge transport layer and photoconductive layer is optimized to reduce impurities, then charge trap density is reduced and image lag characteristics improve, but manufacturing process complexity increases due to controlled deposition requirements
Solution Approach 1:
The patent applies parameter changes by controlling the stoichiometry of the antimony sulfide charge transport layer, specifically varying the sulfur content (Sb2-xS3 composition) across the layer thickness. This compositional parameter variation during deposition allows optimization of the interface region to minimize impurity traps while maintaining overall layer functionality, achieving high interface purity through material composition control rather than complex process steps.
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
This configuration reduces charge trap density, enhancing image quality by improving short-term and long-term lag characteristics and preventing light from reaching the photoconductive layer, thus minimizing dark current and image lag.
Implementation Method 1
a photoconductive layer that generates electric charges by receiving a recording electromagnetic wave representing a radiation image
Implementation Method 2
a substrate side charge transport layer that transports the electric charges generated in the photoconductive layer
Data Source
AI summary
In a radiation image detection apparatus having a radiation image detector that includes the following stacked in the order listed below: a bias electrode, a photoconductive layer, a substrate side charge transport layer, and an active matrix substrate, the radiation image detector does not include an area adjacent to the interface between the substrate side charge transport layer and photoconductive layer having an oxygen or chlorine element density not less than two times the average density of oxygen or chlorine element in the substrate side charge transport layer.