We proposed a compact and radiation-tolerant dosimeter without power supply using the solar cells such as CdTe, Cu(In,Ga)Se₂ (CIGS), and InGaP solar cells. In the CdTe solar cells, linear increase in current due to ⁶⁰Co gamma-ray absorption was confirmed. The change rate of current density increased with increase in the reverse bias voltage, probably due to the increase in the depletion layer width.

We reported the photoluminescence (PL) properties of thallium bromide- (TlBr) crystals exhibiting high performance as γ-ray detectors. The excitation intensity dependence of PL emission intensity and the location dependence of PL spectra were investigated. It was found that the TlBr crystals with higher mobility-lifetime products has higher emission intensity of PL spectrum on the high energy side. The PL of TlBr crystals are attributed to free exciton of indirect band gap and defect levels. Difference in emission intensity is obtained depending on the location of the TlBr crystals as a whole.

Tl-based compound semiconductor shows low-dimensional crystal structure due to the arrangement of Tl atoms. In TlInS₂, Tl atoms show two-dimensional layered structure, Fe doping into TlInS₂ induces broad photo-absorption peaks below the band gap. However, It is unknown how the result of the optical properties originating from the Fe-doping model due to the band structure and density of state. We research clarifies how doping changes electronic structure and optical properties using First-principles calculation. In results, Fe-doping produces d+s-orbital bands within the band gap of TlInS₂. Originating from these bands, new optical transitions appear below the band gap, in agreement with experiment. These transitions might increase the dielectric constant.

The CZTS thin film was immersed in sulfuric acid with iron nitrate (III) nonahydrate. Samples were evaluated by Raman scattering spectroscopy, SEM and EDX. The normalized film thickness decreased with increasing in concentsation of Fe(NO₃)₃・9H₂O. Therefore, sulfuric acid with Fe(NO₃)₃・9H₂O is one of the etchants for CZTS materials.

Solar cells made of lead halide perovskites like CH₃NH₃PbI₃ have attracted much attention because of their high efficiency around 23%. In this work, we study the stability and electronic properties of various substitutional dopants, using the first-principles calculations. We found that the Te and Po dopings are effective to realize the p-type system, while the Bi₂Se codoping is useful to produce the n-type syetem.

Sulfur anneal treatment of CuInS₂ films deposited by PLD method was carried out. For S anneal treatment, the composition ratio of S was performed to be more 50% and the crystal grain size became larger. In addition, it was confirmed that different phases such as Cu₂S which were observed on as-deposited films, disappeared by anneal treatment with temperatures more than 550 ℃.

CuInSe₂ crystals have been prepared at 1050℃ using compound substances as sources. We investigated the possibility of making crystals of using X-ray diffraction and evaluated the samples by surface morphology. The crystals show the X-ray diffraction pattern of CuInSe₂ with chalcopyrite structure.

Cu₂ZnSnS₄ (CZTS) polycrystalline target having a uniform composition were prepared by solid phase reaction method with CZTS polycrystal, ZnS, SnS, and S powders. CZTS films were deposited on a soda-lime glass substrate using the target having Cu-poor, Zn-rich, and S-rich composition ratio by pulse laser deposition (PLD). We confirmed that composition control of CZTS polycrystalline target is effective for improving composition of CZTS thin films.

Cu₂ZnSnS₄ bulk crystals were synthesized by spark plasma sintering (SPS) method. The quantitative ratio of the Cu₂ZnSnS₄ phase was estimated at more than 98 vol.% by Rietveld method. The broad emission band peaked at about 1.25 eV observed in Photoluminescence spectra. This emission was disappeared after the sulfur annealing. At the same time, resistivity decreased and the carrier density increased. After the following annealing in vacuum, those values were returned again. The Hall mobility was quite low.

Cu-Sn-Si (CTSi) precursors were prepared by a solution coating method, which is a low cost and a non-vacuum process, and then the Cu-Sn-Si-S (CTSiS) thin films were fabricated through a sulfurization process. The prepared CTSiS thin films were evaluated by XRD, EPMA, SEM, Raman spectroscopy.

In this research, the Cu-Sn-Si(CTSi) precursors were prepared by applying raw material powder on substrate and heat treatment, and subsequently sulfurized at high temperature to grow Cu-Sn-Si-S(CTSiS) thin films. The thin films were then evaluated by XRD, EPMA and SEM.

Cu₂SnS₃(CTS) can be adjusted to a band gap energy suitable for a solar cell by adding Ge. A method for preparing Cu₂Sn_1-xGe_xS₃(CTGS) thin films by sol-gel sulfurization method was investigated. Precursors were deposited by spin coating of Cu, Sn and Ge containing solution. The precursors were sulfurized at H₂S(3%)+N₂ atmosphere. XRD analysis of the samples showed shifting CTS peaks.

The mist CVD method is a low cost thin film deposition process in a non-vacuum. Cu₂SnS₃ thin films were fabricated by mist CVD method and the thin films were analyzed by XRD, EPMA, SEM and transmittance and reflectance measurement. From the XRD result the deposited film contained (111) of monoclinic Cu₂SnS₃ and (101) of SnO₂.

Tin Sulfide (SnS) layer were annealed at 620℃ for 5 min with SnS powder to enlarge the crystalline grain size. While after annealing the Sn₂S₃ was formed on the surface. This result indicates that a SnS powder may partially evaporated to sulfur vapor while increasing the temperature and react with the SnS thin films.

Intelligent window can be realized by combing transparent thermal insulator and electronic device. The thermal insulator VO₂ thin film using VO₂ target by RF sputtering was demonstrated. The band alignment of NiO-TTFT between p-type NiO and different oxide/nitride-based insulators was investigated.

Visible-light transparent solar cells were fabricated by p-type NiO and n-type ZnO. These solar cells were performed the bending test, then investigated the influence on solar cell characteristics. The p-NiO/n-ZnO solar cells demonstrated outstanding environmental resistance.

ZnO nanorods, which is an n-type transparent semiconductor, and a CuBr_1-xI_x (CuBrI) thin film which is a p-type transparent semiconductor, was deposited on a glass substrates by spin coating and dip coating method to prepare transparent fine structure pn junctions. I-V measurement showed the rectification characteristics of the prepared transparent microstructure pn junction sample.

CuBr_1-xI_x thin films were prepared as a p-type transparent semiconductor by a spin coating method. Photoluminescence (PL) of CuBr_1-xI_x thin films with several chemical composition ratios of x was observed. The shift of PL peak depending on the composition ratio x was observed.

The time-resolved photo-induced deformation phenomena in ternary thallium compounds has been investigated with milliseconds pulsed laser beams. Appropriate pump pulse width to increase the deformation is found by tuning the width of pump pulse in the experiment, and the results show the phenomena is dueto the thermal expansion by the rapid temperature raise around the pump spot region.

Inorganic ternary thallium compounds show a localized and enormous change of the surface relief by light irradiation. In this study, the relationship betweenphoto-induced deformation and crystallographic anisotropy has been investigated for layered ternary thallium compounds. The results show that the anisotropy of the heat conductivity is a key factor for the anisotropic profile of the photo-induced deformation.

In this study, the ellipsometric measurements have been performed to multilayered semiconductor nanocrystals deposited by Layer-by-Layer method. The obtained dielectric function spectra show a change related to the number of nanocrystal layers. The effects of interaction between semiconductor nanocrystal layers are found in the dielectric function spectra.

To obtain the divalent Eu emission from phosphate phosphor which is important for phosphor applications, heat treatments under reducing atmosphere at high temperature are required usually. We have found that the divalent emission can be also obtained by laser irradiation. In this study, the reduction processes in KSr_1-xBa_xPO₄:Eu alloy system have been examined and constructed an optical reduction scheme in order to clarify the difference between the chemical and optical reduction processes.

The temperature dependence of crystal field parameters on Eu³⁺ ion in [Eu(fod)₃]₂(μ-bpm) complex is obtained from ⁵D₀→⁷F₁ transition energies of Eu³⁺ ion with assumption of the simple overlap model for crystal field parameters.