Fabrication and photoelectric conversion of densely packed C60-ethylenediamine adduct microparticle films-modified electrode covered with electrochemically deposited polythiophene thin-films.

Polythiophene-modified densely packed C60-ethylenediamine adduct microparticle films were prepared using a combination of liquid-liquid interfacial precipitation of the adduct microparticles and electrochemical polymerization of 2,2'-bithiophene. The amount of polythiophene was varied as a function of scanning cycles of the applied potential during electrochemical polymerization. Fluorescence-emission properties of these composite films suggested the role of C60-ethylenediamine adduct microparticle film as a photosensitizer in addition to an electron acceptor for polythiophene. Furthermore, cathodic photocurrents were generated via excitation of C60-ethylenediamine adduct microparticle film and polythiophenes using the half-photocell properties of the electrode modified with composite film in the presence of methylviologen.

Dependence of electric power flow on solar radiation power in compact photovoltaic system containing SiC-based inverter with spherical Si solar cells.

A photovoltaic power generation system suitable for mobile applications was developed. A SiC integrated converter with the maximum power point tracking circuit provided the smallest photovoltaic inverter in ~200 W level. The SiC-based inverter exhibited a peak direct current (DC)-alternating current (AC) conversion efficiency higher than that of conventional Si inverters. A Li-ion laminated battery was mounted in the same housing as the inverter. The weight of entire system containing spherical Si solar cell panels was well below 6 kg. Continuous operation measurements of this system were carried out using four solar cell modules connected in parallel under irradiation by natural sunlight. The total inverter efficiencies under realistic operation conditions were slightly decreased compared with the DC-AC converter values because of loss by the maximum power point tracking device. Even under unstable weather conditions, the system provided power stability without ripples. The behaviors of the output powers of the solar cell, storage battery, and inverter modules were analyzed as a function of the solar radiation power density. The substantial efficiencies of the solar cell modules were dependent on the weather conditions and were approximately 10% on cloudy days. The present compact photovoltaic power generation system with SiC device and spherical Si solar cells is viable for sub kW-class inverter.

Additive effects of alkali metals on Cu-modified CH3NH3PbI3-δ Cl δ photovoltaic devices.

We investigated the addition of alkali metal elements (namely Na+, K+, Rb+, and Cs+) to Cu-modified CH3NH3PbI3-δ Cl δ photovoltaic devices and their effects on the photovoltaic properties and electronic structure. The open-circuit voltage was increased by CuBr2 addition to the CH3NH3PbI3-δ Cl δ precursor solution. The series resistance was decreased by simultaneous addition of CuBr2 and RbI, which increased the external quantum efficiencies in the range of 300-500 nm, and the short-circuit current density. The energy gap of the perovskite crystal increased through CuBr2 addition, which we also confirmed by first-principles calculations. Charge carrier generation was observed in the range of 300-500 nm as an increase of the external quantum efficiency, owing to the partial density of states contributed by alkali metal elements. Calculations suggested that the Gibbs energies were decreased by incorporation of alkali metal elements into the perovskite crystals. The conversion efficiency was maintained for 7 weeks for devices with added CuBr2 and RbI.

Stability Characterization of PbI2-Added CH3NH3PbI3- xCl x Photovoltaic Devices.

The stability of TiO2/CH3NH3PbI3- xCl x-based photovoltaic devices in ambient air was evaluated upon adding PbI2 and/or PbCl2. X-ray diffraction (XRD) peak intensities corresponding to the perovskite phase were increased by adding PbI2. After 7 weeks, the XRD peak intensities corresponding to the perovskite phase decreased and those corresponding to PbI2 increased. The reaction rate constants for the decomposition of perovskite and formation of PbI2 were estimated from these data. Thermodynamic calculations of the reaction between PbCl2 and I2 suggested that the formation of PbI2 was not related to the added PbCl2 but rather to excess PbI2. Open-circuit voltages and fill factors of the devices were improved with the 7 week time lapse because of the suppression of electron-hole recombination by the PbI2. In addition, the decomposition of perovskite grains was suppressed by the added PbI2. The I content of the perovskite phase decreased with the 7 week time lapse. However, the Cl content was largely constant after the 7 weeks, which suggested that Cl doping effectively stabilized the perovskite photovoltaic devices.

Effects of transition metals incorporated into perovskite crystals on the electronic structures and magnetic properties by first-principles calculation.

Additive effects of transition metals (M = Cr2+, Co2+, Cu2+ and Y3+) on the electronic structures and magnetic properties of formamidinium lead halide perovskite compounds (FAPbI3, where FA = NH2CHNH2+) were investigated by first-principle calculation using density functional theory. In the case of Cr2+, Cu2+ and Y3+-incorporated FAPbI3 perovskite crystals, the electron density distribution of d-p hybrid orbital on the transition metal and iodine halogen-atoms were delocalized at frontier orbital. The total and partial density of state appeared the 3d-p hybrid orbital near the frontier orbital with narrowing band gap, yielding the wide broad absorption in the near-infrared region. The electronic correlation worked in between the localized spin on 3d orbital of the metal, and the itinerant carriers on the 5p orbital of the iodine halogen ligand and the 6p orbital of the lead atom in the perovskite crystal. The vibration behavior of the Raman and Infrared spectra were associated with change of polarization and slight distortion near the coordination structure. The considerable splitting of chemical shift of 127I-NMR and 207Pb-NMR in the Co2+ and Cu2+-incorporated FAPbI3 crystals were caused by crystal field splitting as Jahn-Teller effect with nearest-neighbor nuclear quadrupole interaction based on the charge distribution.

Highly (100)-oriented CH3NH3PbI3(Cl) perovskite solar cells prepared with NH4Cl using an air blow method.

The effects of adding NH4Cl via an air blow process on CH3NH3PbI3(Cl) perovskite solar cells were investigated. CH3NH3PbI3(Cl) solar cells containing various amounts of NH4Cl were fabricated by spin-coating. The microstructures of the resulting cells were investigated by X-ray diffraction, optical microscopy, and scanning electron microscopy. The current density-voltage characteristics of the cell were improved by adding an appropriate amount of NH4Cl and air blowing, which increased the photoconversion efficiency to 14%. Microstructure analysis indicated that the perovskite layer contained dense grains with strong (100) orientation, as a result of NH4Cl addition and air blowing. The ratio of the (100)/(210) reflection intensities for the perovskite crystals was 2000 times higher than that of randomly oriented grains. The devices were stable when stored in ambient air for two weeks.

Role of electrolytes in the preparation of nanoparticles via the emulsion polymerization of vinyl pivalate.

By controlling both the kind of ion and the ionic strength of electrolytes in an emulsion polymerization system of vinyl pivalate containing about 1% sodium lauryl sulfate as a surfactant, nanoparticles of polyvinylpivalate having a diameter of about 25 nm were successfully prepared. The use of high concentrations of lithium chloride and lithium sulfate (approximately 1.0 mol L(-1)) prevented the nanoparticles from aggregating and produced nanoparticles sizes of 25-50 nm. Ammonium acetate and sodium acetate, on the other hand, accelerated the aggregate of the nanoparticles. These phenomena were examined in detail and found to be similar to the Hofmeister phenomena and the combination rule proposed by Craig et al.

Concentration determination of oxygen nanobubbles in electrolyzed water.

Water electrolysis is well known to produce solutions supersaturated with oxygen. The oxygen in electrolyzed solutions was analyzed with a dissolved oxygen meter and the Winkler method of chemical analysis. The concentration of oxygen measured with the dissolved oxygen meter agreed with that obtained using the Winkler method. However, measurements using a 10-fold dilution method showed a larger concentration of dissolved oxygen compared to the above methods. We developed a modified Winkler method to measure total oxygen concentration more accurately, which agreed with the results obtained from the 10-fold dilution experiment. The difference in measurements is due to the existence of oxygen nanobubbles, as confirmed by the observation of dynamic light scattering using a laser. Further analysis of the oxygen nanobubbles demonstrated that the stability of the nanobubbles was sufficient for chemical reaction and solvation to bulk solution.

Controlling the morphology of Ag nanoclusters by ion implantation to different doses and subsequent annealing.

Ag ions were implanted at 200 keV into silica with nominal doses ranging from 5x10(16) to 2x10(17) ions/cm2. We find that nanovoid-containing Ag nanoclusters form in the implanted samples with doses higher than 1x10(17) ions/cm2. When the dose is increased to 2x10(17) ions/cm2, the nanovoids gradually shrink and form a sandwiched nanocluster-nanovoid-nanocluster structure. The evolution of sandwiched nanoclusters during annealing was observed by in situ transmission electron microscopy experiments. Potential mechanisms for the formation and evolution of the irradiation-induced nanovoids and the sandwiched structure nanoclusters with increasing doses are discussed. The structural optimization of the sandwiched structure nanoclusters was performed by molecular mechanics calculations.

Synthesis and structures of iron nanoparticles coated with boron nitride nanomaterials.

Iron (Fe) nanoparticles coated with boron nitride (BN) nanomaterials were synthesized by using Fe(4)N and B powders as raw materials. The Fe(4)N was reduced to alpha-Fe during annealing at 1000 degrees C for several hours with flowing 100 sccm N(2) gas. The reaction was predicted by Ellingham diagram. The atomic structure and magnetic properties were investigated by high-resolution electron microscopy and vibrating sample magnetometer system.

Atomic structures of multi-walled boron nitride nanohorns.

Boron nitride (BN) nanohorns were synthesized by an arc-melting method, and atomic structure models for BN nanohorns with tetragonal BN rings were proposed from high-resolution electron microscopy and image calculation. Stability and electronic structures of the BN nanohorns were investigated by molecular orbital calculations, comparing with carbon nanohorns. The calculation showed that multi-walled BN nanohorns would be stabilized by the stacking of BN nanohorns. An energy gap of BN nanohorn was calculated to be 0.80 eV, which is lower compared to those of BN clusters and nanotubes.

Three-dimensional imaging of YB56 by high-resolution electron microscopy.

The three-dimensional potential map of YB56 was obtained by inverse Fourier transformation of three-dimensional phases and amplitudes in three high-resolution images taken along the [100], [110] and [111] directions of YB56 crystals; the size of the imaging region was 14 nm x 14 nm x approximately 4 nm, and the image directly showed the three-dimensional potential map of the crystal, a useful method for three-dimensional structure analysis in nanoscale regions.

The First Structure Determination of Nanosized Colloidal Particles of Pd3 P by High-Resolution Electron Microscopy.

The exact three-dimensional structure of a nanosized colloidal particle of Pd3 P was determined directly from high-resolution transmission electron microscopy (HRTEM) images that were recorded in several crystallographic directions. An HRTEM image recorded along [011] is shown on the right. The cores of the particles were excluded from the analysis because of severe multiple diffraction.