Takeo Oku

Fabrication and characterization of CuO/ZnO solar cells

Cuprous oxide (CuO) and zinc oxide (ZnO) heterojunction solar cells fabricated on indium tin oxide-coated glass were studied. CuO and ZnO films were deposited using a galvanostatic method. Structural, morphological and optoelectronic properties of the CuO/ZnO heterojunction were studied by using X-ray diffraction, atomic force microscopy and light current-voltage characteristics.

Microstructures and photovoltaic properties of perovskite-type CH3NH3PbI3 compounds

TiO2/CH3NH3PbI3-based photovoltaic devices were fabricated. The microstructures of these devices were investigated by X-ray diffraction, transmission electron microscopy, and their calculations. Structure analysis indicated phase transformation of the perovskite structure from a tetragonal to a cubic system by annealing, which resulted in the improvement of photovoltaic properties of the devices. Effects of a multiple spin-coating method using a mixture solution were also investigated. The result showed an increase in the efficiencies of the devices, due to the microstructural change of the perovskite compound layers.

Fabrication and Characterization of ZnO/Cu2O Solar Cells Prepared by Electrodeposition

Cuprous oxide (Cu2O)-based solar cells containing zinc oxide (ZnO) were fabricated on F-doped tin oxide (FTO) by electrodeposition. Cu2O layers were deposited from a pH-adjusted electrolyte consisting of LiOH, NaOH or KOH. A photovoltaic device based on a FTO/ZnO/Cu2O/Au heterojunction structure was prepared using LiOH, and it gave a power conversion efficiency of 1.43% under air mass 1.5 illumination.

Fabrication, nanostructures and electronic properties of nanodiamond-based solar cells

Abstract Nanodiamond-based solar cells were fabricated and the photovoltaic properties were investigated. Fullerene (C 60 ) and fullerenol (C 60 (OH) 10–12 ) were used as n-type semiconductors, and diamond nanoparticles and metal phthalocyanine derivative were used as p-type semiconductors. The nanostructures of the solar cells were investigated by transmission electron microscopy and X-ray diffracometry, and the electronic property was discussed.

Fabrication and characterization of perovskite-based CH3NH3Pb1-xGexI3, CH3NH3Pb1-xTlxI3 and CH3NH3Pb1-xInxI3 photovoltaic devices

Perovskite-type CH3NH3PbI3-based photovoltaic devices were fabricated and characterized. Doping effects of thallium (Tl), indium (In), or germanium (Ge) element on the photovoltaic properties and surface structures of the perovskite phase were investigated. The open circuit voltage increased by Ge addition, and fill factors were improved by adding a small amount of Ge, Tl or In. In addition, the wavelength range of incident photon conversion efficiencies was expanded by the Tl addition.

Effects of hole-transporting layers of perovskite-based solar cells

Fabrication and characterization of the photovoltaic and optical properties, and microstructure of perovskite-based solar cells with lead phthalocyanine (PbPc), zinc phthalocyanine, poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine], and copper(I) thiocyanate as hole-transporting layers were investigated. X-ray diffraction analysis and energy-dispersive X-ray spectroscopy were used to identify surface morphologies of the crystal structure and the elemental composition. Introducing PbPc into perovskite solar cells extended the retaining period of photovoltaic activity and performance. The effects of the hole-transporting layer on incident photon-to-current efficiency were investigated. The energy diagram and photovoltaic mechanism of the perovskite solar cells with the hole-transporting layer are discussed.

Fabrication and Characterization of Copper System Compound Semiconductor Solar Cells

Copper system compound semiconductor solar cells were produced by a spin-coating method, and their cell performance and structures were investigated. Copper indium disulfide- (CIS-) based solar cells with titanium dioxide () were produced on F-doped (FTO). A device based on an FTO/CIS/ structure provided better cell performance compared to that based on FTO//CIS structure. Cupric oxide- (CuO-) and cuprous oxide- (-) based solar cells with fullerene () were also fabricated on FTO and indium tin oxide (ITO). The microstructure and cell performance of the CuO/ heterojunction and the : bulk heterojunction structure were investigated. The photovoltaic devices based on FTO/CuO/ and ITO/: structures provided short-circuit current density of 0.015  and 0.11 , and open-circuit voltage of 0.045 V and 0.17 V under an Air Mass 1.5 illumination, respectively. The microstructures of the active layers were examined by X-ray diffraction and transmission electron microscopy.

Microstructures, optical and photoelectric conversion properties of spherical silicon solar cells with anti-reflection SnOx:F thin films

The microstructures and optical and photoelectric conversion properties of spherical silicon (Si) solar cells were investigated and discussed. The surface of the spherical Si with a pn junction provided high crystallinity, and the lattice constant of the center of Si spheres is larger than that of the surface, which would be due to the lattice distortion by defect structures at the center of Si. The conversion efficiencies of spherical Si solar cells coated with SnOx:F anti-reflection thin films were improved by annealing. The optical absorption and fluorescence of the solar cells increased, and the lattice constants of SnOx:F anti-reflection layers decreased after annealing. The mechanisms of chemical reactions at the Si/metal interface were also discussed.

Microstructures and Photovoltaic Properties of Polysilane-Based Solar Cells

Polysilane/C60-based solar cells were fabricated and investigated. Two-types of devices with bulk heterojunction and heterojunction structures were examined and characterized. Addition of silicon-based polymer to the organic solar cells improved the conversion efficiency by wide optical absorption and high carrier mobility. Microstructures of the solar cells were investigated by using X-ray diffraction and transmission electron microscopy. Energy levels in the present solar cells were discussed.

Microstructures and properties of CH3NH3PbI3−xClx hybrid solar cells

Halide-perovskite CH3NH3PbI3 was produced on mesoporous TiO2 layer by spin-coating a precursor solution of PbCl2 and CH3NH3I in dimethylformamide. The role of the annealing process and chlorine (Cl) doping for the perovskite-phase formation was investigated. It was found that crystallization of the perovskite materials was stimulated by the annealing process, and that longer annealing time is necessary for the Cl-doped perovskite compared with that of non-doped perovskite phase.