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Li L, Tao L, Wang L, Li Y, Li J, Ni Z, Fang Y, Yang D. Monolithic integration of perovskite heterojunction on TFT backplanes through vapor deposition for sensitive and stable x-ray imaging. SCIENCE ADVANCES 2024; 10:eadj8659. [PMID: 38669325 PMCID: PMC11051656 DOI: 10.1126/sciadv.adj8659] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2023] [Accepted: 03/27/2024] [Indexed: 04/28/2024]
Abstract
Metal halide perovskites exhibit substantial potential for advancing next-generation x-ray detection. However, fabricating high-performance pixelated imaging arrays remains challenging due to the substantial dark current density and stability issues associated with common organic-inorganic hybrid perovskites. Here, we develop a vapor deposition method to create the first all-inorganic perovskite heterojunction film. The heterojunction introduction effectively reduces the dark current density of detectors to about 0.8 nA·cm-2, satisfying thin-film transistor (TFT) integration standards, while also increases sensitivity to above 2.6 × 104 μC·Gyair-1·cm-2, thus giving rise to a record low detection limit of <1 nGyair·s-1 among all polycrystalline perovskite-based x-ray detectors. The devices also demonstrate remarkable stability across multifarious demanding working conditions. Last, through monolithic integration of the heterojunction film with a 64 × 64 pixelated TFT array, we have achieved high-resolution real-time x-ray imaging, which paves the way for the application of all-inorganic perovskite in low-dose flat-panel x-ray detection.
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Affiliation(s)
- Liqi Li
- State Key Laboratory of Silicon and Advanced Semiconductor Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou 310027, P. R. China
| | - Liting Tao
- State Key Laboratory of Silicon and Advanced Semiconductor Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou 310027, P. R. China
| | - Lixiang Wang
- State Key Laboratory of Silicon and Advanced Semiconductor Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou 310027, P. R. China
| | - Yuyang Li
- State Key Laboratory of Silicon and Advanced Semiconductor Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou 310027, P. R. China
| | - Jiawen Li
- State Key Laboratory of Silicon and Advanced Semiconductor Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou 310027, P. R. China
| | - Zhenyi Ni
- State Key Laboratory of Silicon and Advanced Semiconductor Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou 310027, P. R. China
| | - Yanjun Fang
- State Key Laboratory of Silicon and Advanced Semiconductor Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou 310027, P. R. China
- Shanxi-Zheda Institute of Advanced Materials and Chemical Engineering, Taiyuan 030024, P. R. China
- Shangyu Institute of Semiconductor Materials, Shaoxing 312366, P. R. China
| | - Deren Yang
- State Key Laboratory of Silicon and Advanced Semiconductor Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou 310027, P. R. China
- Shangyu Institute of Semiconductor Materials, Shaoxing 312366, P. R. China
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Wang Y, Wang C, Men L, Hu Q, Xiao J. Colloidal Synthesis of Hollow Double Perovskite Nanocrystals and Their Applications in X-ray Imaging. Inorg Chem 2024; 63:5734-5742. [PMID: 38478658 DOI: 10.1021/acs.inorgchem.4c00280] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/26/2024]
Abstract
Rare earth-based halide double perovskites are regarded as an emerging class of X-ray scintillation materials. However, the majority of related scintillator applications are still focused on single crystal and powder systems; the application of nanocrystal (NC) scintillators is rarely reported. Here, we present the synthesis of high-purity Cs2NaTbCl6 NCs by an improved hot-injection method. Interestingly, hollow Cs2NaTbCl6 NCs are observed, the monitoring of the growth process indicates that micrometer-sized NaCl is the initial product, and then the NaCl would convert into Cs2NaTbCl6 NCs through the diffusion of Cs+ and Tb3+ into NaCl lattice, and the faster outward diffusion of Na+ results in the formation of hollow NCs. The double perovskite NCs exhibit green light emission, and the photoluminescence intensity can be significantly enhanced through Ce3+ doping. In particular, the Cs2NaTbCl6:5%Ce3+ scintillator exhibits a linear response and a low detection limit of 79.09 nGy/s when exposed to X-rays. Furthermore, a flexible scintillator film for X-ray imaging is prepared by mixing NCs with polymer, showing a high spatial resolution imaging capability of 10 lp/mm. This work provides a new strategy for hollow perovskite NCs and may shed light on the synthesis of related hollow NCs and their applications in X-ray detection.
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Affiliation(s)
- Ying Wang
- Beijing Key Lab of Microstructure and Property of Advanced Materials, College of Materials Science and Engineering, Beijing University of Technology, Beijing 100124, China
| | - Chao Wang
- Beijing Key Lab of Microstructure and Property of Advanced Materials, College of Materials Science and Engineering, Beijing University of Technology, Beijing 100124, China
| | - Luxuan Men
- Beijing Key Lab of Microstructure and Property of Advanced Materials, College of Materials Science and Engineering, Beijing University of Technology, Beijing 100124, China
| | - Qingsong Hu
- Hubei Key Laboratory of Low Dimensional Optoelectronic Materials and Devices, Hubei University of Arts and Science, Xiangyang 441053, China
| | - Jiawen Xiao
- Beijing Key Lab of Microstructure and Property of Advanced Materials, College of Materials Science and Engineering, Beijing University of Technology, Beijing 100124, China
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3
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Guan L, Shi S, Niu X, Guo S, Zhao J, Ji T, Dong H, Jia F, Xiao J, Sun L, Yan C. All-Inorganic Manganese-Based CsMnCl 3 Nanocrystals for X-Ray Imaging. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2022; 9:e2201354. [PMID: 35466546 PMCID: PMC9218781 DOI: 10.1002/advs.202201354] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2022] [Indexed: 06/02/2023]
Abstract
Lead-based halide perovskite nanomaterials with excellent optical properties have aroused great attention in the fields of solar cells, light-emitting diodes, lasing, X-ray imaging, etc. However, the toxicity of lead prompts researchers to develop alternatives to cut down the usage of lead. Herein, all-inorganic manganese-based perovskite derivatives, CsMnCl3 nanocrystals (NCs), with uniform size and morphology have been synthesized successfully via a modified hot-injection method. These NCs have a direct bandgap of 4.08 eV and a broadband emission centered at 660 nm. Through introducing modicum lead (1%) into the CsMnCl3 NCs, the photoluminescence intensity greatly improves, and the quantum yield (PLQY) increases from 0.7% to 21%. Furthermore, the CsMnCl3 :1%Pb NCs feature high-efficiency of X-ray absorption and radioluminescence, which make these NCs promising candidates for X-ray imaging.
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Affiliation(s)
- Lin‐Quan Guan
- Beijing National Laboratory for Molecular SciencesState Key Laboratory of Rare Earth Materials Chemistry and ApplicationsPKU‐HKU Joint Laboratory in Rare Earth Materials and Bioinorganic ChemistryCollege of Chemistry and Molecular EngineeringPeking UniversityBeijing100871P. R. China
| | - Shuo Shi
- Beijing National Laboratory for Molecular SciencesState Key Laboratory of Rare Earth Materials Chemistry and ApplicationsPKU‐HKU Joint Laboratory in Rare Earth Materials and Bioinorganic ChemistryCollege of Chemistry and Molecular EngineeringPeking UniversityBeijing100871P. R. China
| | - Xiao‐Wei Niu
- Institute of Microstructure and Property of Advanced MaterialsBeijing Key Lab of Microstructure and Property of Advanced MaterialsFaculty of Materials and ManufacturingBeijing University of TechnologyBeijing100124P. R. China
| | - Shi‐Chen Guo
- Beijing National Laboratory for Molecular SciencesState Key Laboratory of Rare Earth Materials Chemistry and ApplicationsPKU‐HKU Joint Laboratory in Rare Earth Materials and Bioinorganic ChemistryCollege of Chemistry and Molecular EngineeringPeking UniversityBeijing100871P. R. China
| | - Jian Zhao
- Beijing National Laboratory for Molecular SciencesState Key Laboratory of Rare Earth Materials Chemistry and ApplicationsPKU‐HKU Joint Laboratory in Rare Earth Materials and Bioinorganic ChemistryCollege of Chemistry and Molecular EngineeringPeking UniversityBeijing100871P. R. China
| | - Tian‐Meng Ji
- Beijing National Laboratory for Molecular SciencesState Key Laboratory of Rare Earth Materials Chemistry and ApplicationsPKU‐HKU Joint Laboratory in Rare Earth Materials and Bioinorganic ChemistryCollege of Chemistry and Molecular EngineeringPeking UniversityBeijing100871P. R. China
| | - Hao Dong
- Beijing National Laboratory for Molecular SciencesState Key Laboratory of Rare Earth Materials Chemistry and ApplicationsPKU‐HKU Joint Laboratory in Rare Earth Materials and Bioinorganic ChemistryCollege of Chemistry and Molecular EngineeringPeking UniversityBeijing100871P. R. China
| | - Feng‐Yan Jia
- Beijing National Laboratory for Molecular SciencesState Key Laboratory of Rare Earth Materials Chemistry and ApplicationsPKU‐HKU Joint Laboratory in Rare Earth Materials and Bioinorganic ChemistryCollege of Chemistry and Molecular EngineeringPeking UniversityBeijing100871P. R. China
| | - Jia‐Wen Xiao
- Institute of Microstructure and Property of Advanced MaterialsBeijing Key Lab of Microstructure and Property of Advanced MaterialsFaculty of Materials and ManufacturingBeijing University of TechnologyBeijing100124P. R. China
| | - Ling‐Dong Sun
- Beijing National Laboratory for Molecular SciencesState Key Laboratory of Rare Earth Materials Chemistry and ApplicationsPKU‐HKU Joint Laboratory in Rare Earth Materials and Bioinorganic ChemistryCollege of Chemistry and Molecular EngineeringPeking UniversityBeijing100871P. R. China
| | - Chun‐Hua Yan
- Beijing National Laboratory for Molecular SciencesState Key Laboratory of Rare Earth Materials Chemistry and ApplicationsPKU‐HKU Joint Laboratory in Rare Earth Materials and Bioinorganic ChemistryCollege of Chemistry and Molecular EngineeringPeking UniversityBeijing100871P. R. China
- College of Chemistry and Chemical EngineeringLanzhou UniversityLanzhou730000P. R. China
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Effects of Charge Carrier Trapping on Image Resolution of Multilayer Photoconductive Detectors: Application to Amorphous Selenium X-ray Detectors. RADIATION 2022. [DOI: 10.3390/radiation2010007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
The effects of charge carrier trapping on image resolution in multilayer photoconductive imaging detectors was analyzed by developing an analytical model for calculating the modulation transfer function (MTF) of the imaging detectors. The MTF model was developed by considering the charge carrier trapping/recombination in the blocking layer and the distributed trapping in the bulk photoconductor layer of multilayer photoconductive imaging detectors. The relative importance of the bulk and blocking layer trapping, as well as the K-fluorescence reabsorption on the resolution, was also analyzed. The model was applied to amorphous selenium- (a-Se) based multilayer detectors for both chest radiographic and mammographic applications. The theoretical model agreed well with experimental results. The charge carrier trapping/recombination in the blocking layer and K-fluorescence reabsorption mainly controlled the resolution of the a-Se mammographic detectors. In addition to these two effects, the bulk trapping also had a significant effect on the resolution of chest radiographic detectors. The blocking layer thickness had more of a profound effect on the resolution than the amount of trap centers in the blocking layer. The resolution deteriorated drastically with increased blocking layer thickness.
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Zhou Q, Ren J, Xiao J, Lei L, Liao F, Di H, Wang C, Yang L, Chen Q, Yang X, Zhao Y, Han X. Highly efficient copper halide scintillators for high-performance and dynamic X-ray imaging. NANOSCALE 2021; 13:19894-19902. [PMID: 34761770 DOI: 10.1039/d1nr03996b] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Progress towards high performance X-ray detection and dynamic imaging applications, including nondestructive inspection, homeland security, and medical diagnostics, requires scintillators with a high light yield, a reasonable decay time, low cost, and eco-friendliness. Recently, copper halide scintillators have drawn tremendous attention due to their outstanding radioluminescence performance. Here, we first employed β-Cs3Cu2Cl5 as a high-performance scintillator, with a photoluminescence quantum yield (PLQY) of 94.6%, a radioluminescence light yield of 34 000 ± 4000 photons per MeV, a low detection limit of 81.7 nGyair s-1, and good operational stability under a total X-ray dose of 174.6 Gyair in air. In addition, this scintillator presents a high spatial resolution of 9.6 lp mm-1 at the modulation transfer function of 0.2 and a superb performance at 60 frames per second in our X-ray imaging system. Overall, this highly efficient scintillator demonstrates outstanding comprehensive performance and shows great potential for broad applications in X-ray detection and dynamic imaging.
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Affiliation(s)
- Quan Zhou
- Institute of Materials, China Academy of Engineering Physics, Jiangyou 621908, China.
- Institute of Microstructure and Property of Advanced Materials, Beijing Key Lab of Microstructure and Property of Advanced Materials, Faculty of Materials and Manufacturing, Beijing University of Technology, Beijing 100124, China.
| | - Jiwei Ren
- Institute of Materials, China Academy of Engineering Physics, Jiangyou 621908, China.
| | - Jiawen Xiao
- Institute of Microstructure and Property of Advanced Materials, Beijing Key Lab of Microstructure and Property of Advanced Materials, Faculty of Materials and Manufacturing, Beijing University of Technology, Beijing 100124, China.
| | - Lin Lei
- Institute of Materials, China Academy of Engineering Physics, Jiangyou 621908, China.
| | - Feiyi Liao
- Institute of Materials, China Academy of Engineering Physics, Jiangyou 621908, China.
| | - Haipeng Di
- Institute of Materials, China Academy of Engineering Physics, Jiangyou 621908, China.
| | - Chao Wang
- Institute of Microstructure and Property of Advanced Materials, Beijing Key Lab of Microstructure and Property of Advanced Materials, Faculty of Materials and Manufacturing, Beijing University of Technology, Beijing 100124, China.
| | - Lijun Yang
- Institute of Materials, China Academy of Engineering Physics, Jiangyou 621908, China.
| | - Qi Chen
- School of Materials Science & Engineering, Beijing Institute of Technology, Beijing 100081, China
| | - Xiaofang Yang
- College of Materials Science and Engineering, Chongqing University, Chongqing 400044, China
| | - Yiying Zhao
- Institute of Materials, China Academy of Engineering Physics, Jiangyou 621908, China.
| | - Xiaodong Han
- Institute of Microstructure and Property of Advanced Materials, Beijing Key Lab of Microstructure and Property of Advanced Materials, Faculty of Materials and Manufacturing, Beijing University of Technology, Beijing 100124, China.
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Zhu W, Ma W, Su Y, Chen Z, Chen X, Ma Y, Bai L, Xiao W, Liu T, Zhu H, Liu X, Liu H, Liu X, Yang Y(M. Low-dose real-time X-ray imaging with nontoxic double perovskite scintillators. LIGHT, SCIENCE & APPLICATIONS 2020; 9:112. [PMID: 32637079 PMCID: PMC7327019 DOI: 10.1038/s41377-020-00353-0] [Citation(s) in RCA: 97] [Impact Index Per Article: 24.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2020] [Revised: 06/12/2020] [Accepted: 06/17/2020] [Indexed: 05/03/2023]
Abstract
X-rays are widely used in probing inside information nondestructively, enabling broad applications in the medical radiography and electronic industries. X-ray imaging based on emerging lead halide perovskite scintillators has received extensive attention recently. However, the strong self-absorption, relatively low light yield and lead toxicity of these perovskites restrict their practical applications. Here, we report a series of nontoxic double-perovskite scintillators of Cs2Ag0.6Na0.4In1-yBiyCl6. By controlling the content of the heavy atom Bi3+, the X-ray absorption coefficient, radiative emission efficiency, light yield and light decay were manipulated to maximise the scintillator performance. A light yield of up to 39,000 ± 7000 photons/MeV for Cs2Ag0.6Na0.4In0.85Bi0.15Cl6 was obtained, which is much higher than that for the previously reported lead halide perovskite colloidal CsPbBr3 (21,000 photons/MeV). The large Stokes shift between the radioluminescence (RL) and absorption spectra benefiting from self-trapped excitons (STEs) led to a negligible self-absorption effect. Given the high light output and fast light decay of this scintillator, static X-ray imaging was attained under an extremely low dose of ∼1 μGyair, and dynamic X-ray imaging of finger bending without a ghosting effect was demonstrated under a low-dose rate of 47.2 μGyair s-1. After thermal treatment at 85 °C for 50 h followed by X-ray irradiation for 50 h in ambient air, the scintillator performance in terms of the RL intensity and X-ray image quality remained almost unchanged. Our results shed light on exploring highly competitive scintillators beyond the scope of lead halide perovskites, not only for avoiding toxicity but also for better performance.
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Affiliation(s)
- Wenjuan Zhu
- State Key Laboratory of Modern Optical Instrumentation, College of Optical Science and Engineering, International Research Center for Advanced Photonics, Zhejiang University, Hangzhou, Zhejiang China
| | - Wenbo Ma
- State Key Laboratory of Modern Optical Instrumentation, College of Optical Science and Engineering, International Research Center for Advanced Photonics, Zhejiang University, Hangzhou, Zhejiang China
| | - Yirong Su
- State Key Laboratory of Modern Optical Instrumentation, College of Optical Science and Engineering, International Research Center for Advanced Photonics, Zhejiang University, Hangzhou, Zhejiang China
| | - Zeng Chen
- Center for Chemistry of High-Performance & Novel Materials, department of Chemistry, Zhejiang University, Hangzhou, Zhejiang China
| | - Xinya Chen
- State Key Laboratory of Modern Optical Instrumentation, College of Optical Science and Engineering, International Research Center for Advanced Photonics, Zhejiang University, Hangzhou, Zhejiang China
| | - Yaoguang Ma
- State Key Laboratory of Modern Optical Instrumentation, College of Optical Science and Engineering, International Research Center for Advanced Photonics, Zhejiang University, Hangzhou, Zhejiang China
| | - Lizhong Bai
- State Key Laboratory of Modern Optical Instrumentation, College of Optical Science and Engineering, International Research Center for Advanced Photonics, Zhejiang University, Hangzhou, Zhejiang China
| | - Wenge Xiao
- State Key Laboratory of Modern Optical Instrumentation, College of Optical Science and Engineering, International Research Center for Advanced Photonics, Zhejiang University, Hangzhou, Zhejiang China
| | - Tianyu Liu
- State Key Laboratory of Modern Optical Instrumentation, College of Optical Science and Engineering, International Research Center for Advanced Photonics, Zhejiang University, Hangzhou, Zhejiang China
| | - Haiming Zhu
- Center for Chemistry of High-Performance & Novel Materials, department of Chemistry, Zhejiang University, Hangzhou, Zhejiang China
| | - Xiaofeng Liu
- State Key Laboratory of Modern Optical Instrumentation, College of Optical Science and Engineering, International Research Center for Advanced Photonics, Zhejiang University, Hangzhou, Zhejiang China
| | - Huafeng Liu
- State Key Laboratory of Modern Optical Instrumentation, College of Optical Science and Engineering, International Research Center for Advanced Photonics, Zhejiang University, Hangzhou, Zhejiang China
| | - Xu Liu
- State Key Laboratory of Modern Optical Instrumentation, College of Optical Science and Engineering, International Research Center for Advanced Photonics, Zhejiang University, Hangzhou, Zhejiang China
| | - Yang (Michael) Yang
- State Key Laboratory of Modern Optical Instrumentation, College of Optical Science and Engineering, International Research Center for Advanced Photonics, Zhejiang University, Hangzhou, Zhejiang China
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Arnab SM, Kabir MZ. A Novel Amorphous Selenium Avalanche Detector Structure for Low Dose Medical X-Ray Imaging. IEEE TRANSACTIONS ON RADIATION AND PLASMA MEDICAL SCIENCES 2020. [DOI: 10.1109/trpms.2019.2937678] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Heo JH, Shin DH, Park JK, Kim DH, Lee SJ, Im SH. High-Performance Next-Generation Perovskite Nanocrystal Scintillator for Nondestructive X-Ray Imaging. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2018; 30:e1801743. [PMID: 30141200 DOI: 10.1002/adma.201801743] [Citation(s) in RCA: 129] [Impact Index Per Article: 21.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2018] [Revised: 05/28/2018] [Indexed: 05/12/2023]
Abstract
Readily commercializable and cost-effective next-generation CsPbBr3 perovskite nanocrystals (PNCs) based X-ray detectors are demonstrated. The PNCs-based X-ray detector exhibits higher spatial resolution (9.8 lp mm-1 at modulation transfer function (MTF) = 0.2 and 12.5-8.9 lp mm-1 for a linear line chart), faster response time (≈200 ns), and comparable stability (>40 Gyair s-1 of X-ray exposure) compared with the commercialized terbium-doped gadolinium oxysulfide (GOS)-based detectors (spatial resolution = 6.2 lp mm-1 at MTF = 0.2 and 6.3 lp mm-1 for a linear line chart, response time = ≈1200 ns) because the PNCs-based scintillator has ≈5.6-fold faster average photoluminescence lifetime and stronger emission than the GOS-based one.
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Affiliation(s)
- Jin Hyuck Heo
- Department of Chemical and Biological engineering, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul, 17104, Republic of Korea
| | - Dong Hee Shin
- Department of Chemical and Biological engineering, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul, 17104, Republic of Korea
| | - Jin Kyoung Park
- Department of Chemical and Biological engineering, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul, 17104, Republic of Korea
| | - Do Hun Kim
- Department of Chemical and Biological engineering, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul, 17104, Republic of Korea
| | - Sang Jin Lee
- Department of Chemical and Biological engineering, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul, 17104, Republic of Korea
| | - Sang Hyuk Im
- Department of Chemical and Biological engineering, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul, 17104, Republic of Korea
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Photoconductors for X-Ray Image Detectors. SPRINGER HANDBOOK OF ELECTRONIC AND PHOTONIC MATERIALS 2017. [DOI: 10.1007/978-3-319-48933-9_45] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
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Kasap S, Frey JB, Belev G, Tousignant O, Mani H, Greenspan J, Laperriere L, Bubon O, Reznik A, DeCrescenzo G, Karim KS, Rowlands JA. Amorphous and polycrystalline photoconductors for direct conversion flat panel x-ray image sensors. SENSORS 2011; 11:5112-57. [PMID: 22163893 PMCID: PMC3231396 DOI: 10.3390/s110505112] [Citation(s) in RCA: 114] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/07/2011] [Revised: 04/25/2011] [Accepted: 05/04/2011] [Indexed: 11/29/2022]
Abstract
In the last ten to fifteen years there has been much research in using amorphous and polycrystalline semiconductors as x-ray photoconductors in various x-ray image sensor applications, most notably in flat panel x-ray imagers (FPXIs). We first outline the essential requirements for an ideal large area photoconductor for use in a FPXI, and discuss how some of the current amorphous and polycrystalline semiconductors fulfill these requirements. At present, only stabilized amorphous selenium (doped and alloyed a-Se) has been commercialized, and FPXIs based on a-Se are particularly suitable for mammography, operating at the ideal limit of high detective quantum efficiency (DQE). Further, these FPXIs can also be used in real-time, and have already been used in such applications as tomosynthesis. We discuss some of the important attributes of amorphous and polycrystalline x-ray photoconductors such as their large area deposition ability, charge collection efficiency, x-ray sensitivity, DQE, modulation transfer function (MTF) and the importance of the dark current. We show the importance of charge trapping in limiting not only the sensitivity but also the resolution of these detectors. Limitations on the maximum acceptable dark current and the corresponding charge collection efficiency jointly impose a practical constraint that many photoconductors fail to satisfy. We discuss the case of a-Se in which the dark current was brought down by three orders of magnitude by the use of special blocking layers to satisfy the dark current constraint. There are also a number of polycrystalline photoconductors, HgI2 and PbO being good examples, that show potential for commercialization in the same way that multilayer stabilized a-Se x-ray photoconductors were developed for commercial applications. We highlight the unique nature of avalanche multiplication in a-Se and how it has led to the development of the commercial HARP video-tube. An all solid state version of the HARP has been recently demonstrated with excellent avalanche gains; the latter is expected to lead to a number of novel imaging device applications that would be quantum noise limited. While passive pixel sensors use one TFT (thin film transistor) as a switch at the pixel, active pixel sensors (APSs) have two or more transistors and provide gain at the pixel level. The advantages of APS based x-ray imagers are also discussed with examples.
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Affiliation(s)
- Safa Kasap
- Department of Electrical and Computer Engineering, University of Saskatchewan, Saskatoon, SK, S7N 5A9, Canada; E-Mails: (J.B.F.); (G.B.)
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +1-306-966-5390; Fax: +1-306-966-5407
| | - Joel B. Frey
- Department of Electrical and Computer Engineering, University of Saskatchewan, Saskatoon, SK, S7N 5A9, Canada; E-Mails: (J.B.F.); (G.B.)
| | - George Belev
- Department of Electrical and Computer Engineering, University of Saskatchewan, Saskatoon, SK, S7N 5A9, Canada; E-Mails: (J.B.F.); (G.B.)
| | - Olivier Tousignant
- Anrad Corporation, 4950 rue Lévy, Saint-Laurent, QC, H4R 2P1, Canada; E-Mails: (O.T.); (H.M.); (J.G.); (L.L.)
| | - Habib Mani
- Anrad Corporation, 4950 rue Lévy, Saint-Laurent, QC, H4R 2P1, Canada; E-Mails: (O.T.); (H.M.); (J.G.); (L.L.)
| | - Jonathan Greenspan
- Anrad Corporation, 4950 rue Lévy, Saint-Laurent, QC, H4R 2P1, Canada; E-Mails: (O.T.); (H.M.); (J.G.); (L.L.)
| | - Luc Laperriere
- Anrad Corporation, 4950 rue Lévy, Saint-Laurent, QC, H4R 2P1, Canada; E-Mails: (O.T.); (H.M.); (J.G.); (L.L.)
| | - Oleksandr Bubon
- Department of Physics, Lakehead University, 955 Oliver Road, Thunder Bay, ON, P7B 5E1, Canada; E-Mails: (O.B.); (A.R.)
| | - Alla Reznik
- Department of Physics, Lakehead University, 955 Oliver Road, Thunder Bay, ON, P7B 5E1, Canada; E-Mails: (O.B.); (A.R.)
- Thunder Bay Regional Research Institute, 980 Oliver Road, Thunder Bay, ON, P7B 6V4, Canada; E-Mails: (G.D.); (J.A.R.)
| | - Giovanni DeCrescenzo
- Thunder Bay Regional Research Institute, 980 Oliver Road, Thunder Bay, ON, P7B 6V4, Canada; E-Mails: (G.D.); (J.A.R.)
| | - Karim S. Karim
- Department of Electrical and Computer Engineering, University of Waterloo, Waterloo, ON, N2L 3G1, Canada; E-Mail:
| | - John A. Rowlands
- Thunder Bay Regional Research Institute, 980 Oliver Road, Thunder Bay, ON, P7B 6V4, Canada; E-Mails: (G.D.); (J.A.R.)
- Imaging Research, Sunnybrook Health Sciences Centre, University of Toronto, 2075 Bayview Avenue, Toronto, ON, M4N 3M5, Canada
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