Yoshihiko Kanemitsu

Bio: Yoshihiko Kanemitsu is an academic researcher from Kyoto University. The author has contributed to research in topics: Photoluminescence & Exciton. The author has an hindex of 58, co-authored 525 publications receiving 14685 citations. Previous affiliations of Yoshihiko Kanemitsu include University of Tokyo & Columbia University.

Photocarrier recombination dynamics in perovskite CH3NH3PbI3 for solar cell applications.

Abstract: Using time-resolved photoluminescence and transient absorption measurements at room temperature, we report excitation-intensity-dependent photocarrier recombination processes in thin films made from the organo-metal halide perovskite semiconductor CH3NH3PbI3 for solar-cell applications. The photocarrier dynamics are well described by a simple rate equation including single-carrier trapping and electron–hole radiative recombination. This result provides clear evidence that the free-carrier model is better than the exciton model for interpreting the optical properties of CH3NH3PbI3. The observed large two-carrier recombination rate suggests the promising potential of perovskite semiconductors for optoelectronic device applications. Our findings provide the information about the dynamical behaviors of photoexcited carriers that is needed for developing high-efficiency perovskite solar cells.

Visible photoluminescence of Ge microcrystals embedded in SiO2 glassy matrices

Abstract: Ge microcrystals embedded in SiO2 glassy matrices were formed by a radio‐frequency magnetron cosputtering technique and then annealed at 800 °C for 30 min. The average radius of the Ge microcrystals in SiO2 was determined to be about 3 nm by means of Raman spectroscopy and high resolution electron microscope. The annealed sample showed a strong room temperature luminescence with a peak at 2.18 eV. This is consistent with quantum confinement of electrons and holes.

Blue-light emission at room temperature from Ar + -irradiated SrTiO 3

Abstract: Oxide-based electronic devices are expected to have fascinating properties, unlike those made from conventional semiconductors. SrTiO3 (STO) is a key material for this new field of electronics1,2,3,4,5,6,7,8,9,10,11. Here we report on blue-light emission at room temperature from Ar+-irradiated, metallic STO. The irradiation introduces oxygen deficiencies to a depth of ∼20 nm from the crystal surface. These deficiencies generate conduction carriers and stabilize a hole level in a self-trapped state. We propose a model by which the doped conduction electrons and the in-gap state produce a radiative process that results in blue-light emission. The emitting region can be patterned into any size and shape with conventional microscopic fabrication techniques.

Visible photoluminescence from oxidized Si nanometer-sized spheres: Exciton confinement on a spherical shell.

Abstract: We report strong visible photoluminescence (PL) at room temperature from oxidized Si nanometer-sized spheres with a spherical crystalline Si (c-Si) core and an amorphous ${\mathrm{SiO}}_{2}$ (a-${\mathrm{SiO}}_{2}$) surface layer. The peak energy of the broad PL spectrum is about 1.65 eV, which is independent of the core diameter. We propose a model in which excitons are confined on a spherical shell, an interfacial layer between the c-Si core and the a-${\mathrm{SiO}}_{2}$ surface layer, and in which the exciton confinement enhances the oscillator strength and the PL intensity.

Microstructure and optical properties of free-standing porous silicon films: Size dependence of absorption spectra in Si nanometer-sized crystallites.

Abstract: We have studied the microstructure and optical properties of free-standing porous Si thin films fabricated by electrochemical anodization. Raman-spectroscopy and transmission-electron-microscopy examinations show that Si crystallite spheres with diameters of several nanometers are dispersed in the amorphous phase. The blueshift of the optical-absorption spectrum is observed for decreasing average diameter of the Si crystallites. However, there is no clear size dependence of the peak energy of the broad photoluminescence (PL) spectrum. Spectroscopic analysis strongly suggests that the photogeneration of carriers occurs in the c-Si core, whose band gap is modified by the quantum-confinement effect, while the strong PL comes from the near-surface region of small crystallites.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Gold nanoparticles: assembly, supramolecular chemistry, quantum-size-related properties, and applications toward biology, catalysis, and nanotechnology.

Abstract: Although gold is the subject of one of the most ancient themes of investigation in science, its renaissance now leads to an exponentially increasing number of publications, especially in the context of emerging nanoscience and nanotechnology with nanoparticles and self-assembled monolayers (SAMs). We will limit the present review to gold nanoparticles (AuNPs), also called gold colloids. AuNPs are the most stable metal nanoparticles, and they present fascinating aspects such as their assembly of multiple types involving materials science, the behavior of the individual particles, size-related electronic, magnetic and optical properties (quantum size effect), and their applications to catalysis and biology. Their promises are in these fields as well as in the bottom-up approach of nanotechnology, and they will be key materials and building block in the 21st century. Whereas the extraction of gold started in the 5th millennium B.C. near Varna (Bulgaria) and reached 10 tons per year in Egypt around 1200-1300 B.C. when the marvelous statue of Touthankamon was constructed, it is probable that “soluble” gold appeared around the 5th or 4th century B.C. in Egypt and China. In antiquity, materials were used in an ecological sense for both aesthetic and curative purposes. Colloidal gold was used to make ruby glass 293 Chem. Rev. 2004, 104, 293−346

Understanding TiO2 photocatalysis: mechanisms and materials.

Abstract: Jenny Schneider,*,† Masaya Matsuoka,‡ Masato Takeuchi,‡ Jinlong Zhang, Yu Horiuchi,‡ Masakazu Anpo,‡ and Detlef W. Bahnemann*,† †Institut fur Technische Chemie, Leibniz Universitaẗ Hannover, Callinstrasse 3, D-30167 Hannover, Germany ‡Faculty of Engineering, Osaka Prefecture University, 1 Gakuen-cho, Sakai Osaka 599-8531, Japan Key Lab for Advanced Materials and Institute of Fine Chemicals, East China University of Science and Technology, Shanghai 200237, China

Control of valley polarization in monolayer MoS2 by optical helicity

Abstract: Circularly polarized light has been used to confine charge carriers in single-layer molybdenum disulphide entirely to a single energy-band valley, representing full valley polarization.