Kengo Shibuya

Bio: Kengo Shibuya is an academic researcher from University of Tokyo. The author has contributed to research in topics: Scintillator & Detector. The author has an hindex of 13, co-authored 64 publications receiving 601 citations. Previous affiliations of Kengo Shibuya include National Institute of Radiological Sciences.

Scintillation properties of (C6H13NH3)2PbI4 : Exciton luminescence of an organic/inorganic multiple quantum well structure compound induced by 2.0 MeV protons

Abstract: We report a new type of scintillator especially suitable for pulse-radiation detection Thin films of organic/inorganic perovskite compound (n-C6H13NH3)2PbI4, which is characterized by a multiple quantum well structure, were bombarded by 20 MeV protons, and their radiation-induced emission spectra were obtained A single and sharp emission peak due to an exciton was observed at the wavelength of 524 nm This emission was clearly detected even at room temperature, and its quantum efficiency was very high The line shape of this emission did not change, retaining its sharpness, and no other emissions appeared throughout the irradiation The optical response of (n-C6H13NH3)2PbI4 is very fast (n-C6H13NH3)2PbI4 is a promising scintillator material, meeting requirements not satisfied by conventional scintillators

Development of ultra-fast semiconducting scintillators using quantum confinement effect

Abstract: The concept of a "quantum scintillator", satisfying both a large light output and a quick response, is proposed. The temporal behavior of scintillation from (n-C6H13NH3)2PbI4, a natural multiple quantum well structure provided by the lead-halide-based perovskite-type organic-inorganic hybrid compound, was investigated using a short-pulsed electron beam and a streak camera. A decay component of 390 ps was efficiently observed even at room temperature. This response is notably quicker than conventional Ce3+-activated scintillators because of a quantum confinement effect that increases the overlapping region of electron and hole wavefunctions in the low-dimensional system. This achievement would be the next breakthrough in the development of ultra-fast inorganic scintillators.

Subnanosecond time-resolved x-ray measurements using an organic-inorganic perovskite scintillator

Abstract: We have developed a fast x-ray detector using an organic-inorganic perovskite scintillator of phenethylamine lead bromide (PhE-PbBr4) The scintillator had a dominant light emission with a fast decay time of 99 ns An x-ray detector equipped with a 09-mm-thick PhE-PbBr4 crystal was used to detect nuclear resonant scattering in N61i (the first excited level: 6741 keV; lifetime: 76 ns) by using synchrotron radiation With this detector, we could successfully record the decaying gamma rays emitted from N61i with a time resolution of 07 ns (full width at half maximum) and a relatively high detection efficiency of 24%

Quantum confinement for large light output from pure semiconducting scintillators

Abstract: A method for creating a fast scintillator is proposed. Recently, much attention has been paid to pure semiconductors during development of subnanosecond fast solid scintillators. However, the bulky samples rarely exhibit high light yields at room temperature because of thermal instability at the excitonic levels. The authors employed the optimum three- and two-dimensional semiconducting systems provided by lead-halide-based compounds to demonstrate the advantage of low dimensionality in the scintillating efficiency. Their dimensional and temperature dependencies were investigated using a high-energy proton beam. Consequently, the quantum confinement system clearly prevented thermal quenching from excitonic level even at room temperature, and the result proposes the next breakthrough to create ultrafast solid scintillators.

Effect of organic moieties on the scintillation properties of organic–inorganic layered perovskite-type compounds

Abstract: The effects of organic moieties on the scintillation properties of organic–inorganic layered perovskite-type compounds have been investigated. Three kinds of single crystals were fabricated, namely, (C4H9NH3)2PbBr4 (C4), (C6H5CH2NH3)2PbBr4 (Ben), and (C6H5C2H4NH3)2PbBr4 (Phe). Among the single crystals, the light output of Phe was found to have the greatest value when exposed to X-ray radiation (67.4 keV). The light output of Phe was 0.62 times that of YAP:Ce. The relative values of the light outputs among the fabricated single crystals under X-ray radiation correlated well with those of the quantum efficiencies and the luminescence intensity under ultraviolet radiation.

Ruddlesden-Popper Hybrid Lead Iodide Perovskite 2D Homologous Semiconductors

Abstract: The hybrid two-dimensional (2D) halide perovskites have recently drawn significant interest because they can serve as excellent photoabsorbers in perovskite solar cells. Here we present the large scale synthesis, crystal structure, and optical characterization of the 2D (CH3(CH2)3NH3)2(CH3NH3)n−1PbnI3n+1 (n = 1, 2, 3, 4, ∞) perovskites, a family of layered compounds with tunable semiconductor characteristics. These materials consist of well-defined inorganic perovskite layers intercalated with bulky butylammonium cations that act as spacers between these fragments, adopting the crystal structure of the Ruddlesden–Popper type. We find that the perovskite thickness (n) can be synthetically controlled by adjusting the ratio between the spacer cation and the small organic cation, thus allowing the isolation of compounds in pure form and large scale. The orthorhombic crystal structures of (CH3(CH2)3NH3)2(CH3NH3)Pb2I7 (n = 2, Cc2m; a = 8.9470(4), b = 39.347(2) A, c = 8.8589(6)), (CH3(CH2)3NH3)2(CH3NH3)2Pb3I10 (...

Two-Dimensional Hybrid Halide Perovskites: Principles and Promises.

Abstract: Hybrid halide perovskites have become the “next big thing” in emerging semiconductor materials, as the past decade witnessed their successful application in high-performance photovoltaics. This resurgence has encompassed enormous and widespread development of the three-dimensional (3D) perovskites, spearheaded by CH3NH3PbI3. The next generation of halide perovskites, however, is characterized by reduced dimensionality perovskites, emphasizing the two-dimensional (2D) perovskite derivatives which expand the field into a more diverse subgroup of semiconducting hybrids that possesses even higher tunability and excellent photophysical properties. In this Perspective, we begin with a historical flashback to early reports before the “perovskite fever”, and we follow this original work to its fruition in the present day, where 2D halide perovskites are in the spotlight of current research, offering characteristics desirable in high-performance optoelectronics. We approach the evolution of 2D halide perovskites f...