Perovskite photodiode-based high sensitivity X-ray detector for use in medical diagnosis

2018 Fiscal Year Final Research Report

• Project/Area Number: 17K19108
• Research Category: Grant-in-Aid for Challenging Research (Exploratory)
• Allocation Type: Multi-year Fund
• Research Field: Physical chemistry, Functional solid state chemistry, and related fields
• Research Institution: Toin University of Yokohama
• Principal Investigator: Miyasaka Tsutomu 桐蔭横浜大学, 医用工学部, 特任教授 【東京大学先端科学技術研究センター・フェロー】 (00350687)
• Project Period (FY): 2017-06-30 – 2019-03-31
• Keywords: X線検出 / 医療診断 / ペロブスカイト / 光電変換 / 光ダイオード

Outline of Final Research Achievements

The fine particles granulated from lead halide perovskite single crystal (MAPbI3) were pressed by a high temperature heating and pressing machine to form a semi-transparent film with a thickness of about 400 microns in which perovskite particles are partially fused. A metal electrode was vapor-deposited on this film to construct a planar device. The device irradiated with X-rays with energy of 20 to 50 eV under external bias of 5 to 20 V produced X-ray-induced current response. Current amplitude proportionally increased with X-ray energy. The device produced a stable current of 5 nA/cm2 or more. It has been found that the background current of the device is highly suppressed as the temperature of the device is lowered, leading to achievement of high signal/noise ratio. The perovskite-based X-ray detector showed high sensitivity that can reach a value close to the commercial X-ray detector using CdTe as photoconductor.

Free Research Field

光電気化学

Academic Significance and Societal Importance of the Research Achievements

X線の検出器は医療において画像診断に用いられておりシンチレータ(発光素子)と光ダイオードの２つを使ってX線の線量を間接的に計測するが、もう1つの方法としてX線を直接に半導体素子の電流応答に変換する方法が使われ、画像分解能の点で優れることが期待さる。しかしこの直接法に用いる半導体はCdTeでありCdの有毒性が問題となる。本研究で用いたペロブスカイトはCdTeに代わる環境有害性の低い薄膜材料であり、学術的にX線に対して高い感度で電流応答をする可能性が明らかになったため、今後、ペロブスカイト結晶薄膜の質を高めることによって更なる性能向上が期待できる。