Radiation Imaging Device With Stacked Organic Photoelectric Conversion
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Solution Overview
Problem
Conventional radiation imaging devices using inorganic photoelectric conversion materials suffer from noise interference and reduced image quality due to broad absorption spectra, and the side-by-side configuration of photoelectric conversion and switching elements leads to a large pixel area and small light-receiving area, compromising image quality.
Innovation Solution
A radiation imaging device with a phosphor film that emits light after absorbing radiation, a photoelectric conversion portion using organic materials, and a signal output portion with an amorphous oxide thin-film transistor, where the signal output and photoelectric conversion portions overlap in the thickness direction, optimizing light absorption and noise reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If inorganic photoelectric conversion materials are used, then the device can detect radiation, but noise interference increases and image quality deteriorates due to broad absorption spectra
Solution Approach 1:
The patent changes the material parameter of the photoelectric conversion film from inorganic materials (amorphous silicon) to organic photoelectric conversion materials. This material substitution narrows the absorption spectrum to match the phosphor emission wavelength, thereby reducing noise interference and improving image quality while maintaining radiation detection capability.
2Area of stationary object
If photoelectric conversion portion and switching element are disposed side by side, then the device structure is simplified, but pixel area becomes large and light-receiving area becomes small
Solution Approach 1:
The patent transitions from a planar side-by-side configuration to a three-dimensional stacked configuration where the photoelectric conversion portion and switching element are disposed one above the other in the thickness direction. This dimensional change allows both components to occupy the same pixel footprint area, maximizing the light-receiving area while maintaining functional integration.
3Reliability
If amorphous silicon is used as photoelectric conversion material, then the material is well-established, but broad absorption spectrum causes noise and reduced image quality
Solution Approach 1:
The patent changes the material composition parameter from inorganic amorphous silicon to organic photoelectric conversion materials. Although organic materials were less established previously, this parameter change enables spectral matching between the phosphor emission and photoelectric conversion absorption, significantly improving image quality while the patent ensures material stability through proper material selection and characterization.
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 effectively suppresses noise interference and enhances image quality by maximizing the light-receiving area while minimizing noise, resulting in higher-definition images.
Implementation Method 1
a phosphor film that emits light by absorbing radiation transmitted through an imaging target
Implementation Method 2
a photoelectric conversion portion that includes an upper electrode, a lower electrode, and a photoelectric conversion film disposed between the upper and lower electrodes, the photoelectric conversion film containing an organic photoelectric conversion material that absorbs light emitted from the phosphor film
Data Source
AI summary
A radiation imaging device 12 has a phosphor film 8; a photoelectric conversion portion 13 including an upper electrode 6, a lower electrode 2, and a photoelectric conversion film 4 disposed between the electrodes; a signal output portion 14 including a field effect thin film transistor 10 having an active layer 24 formed from an amorphous oxide and that outputs a signal corresponding to electric charges generated by the photoelectric conversion portion; and a substrate 1 on which the signal output portion, the photoelectric conversion portion and the phosphor film are formed in this order. Each of pixel portions is made up of the signal output portion, the photoelectric conversion portion and the phosphor film, and the signal output portion and the photoelectric conversion portion in each of the pixel portions are formed so as to have an overlapping portion in a thickness direction.