First-principles materials design of CuInSe2-based high-efficiency photovoltaic solar cells

Based on ab initio   electronic structure calculations by self-interaction-corrected local-density-approximation (SIC-LDA) with the Korringa–Kohn–Rostoker coherent potential approximation (KKR-CPA), we propose a materials design for high efficiency photovoltaic solar cells (PVSCs). It is shown that (i) the concentration dependence of the mixing energy of CuIn_1−xGa_xSe₂${\mathrm{CuIn}}_{1-x}{\mathrm{Ga}}_x{\mathrm{Se}}_2$ shows upward convexity, thus this system favors phase separation. Due to the type II band alignment between CuInSe₂${\mathrm{CuInSe}}_2$ and CuGaSe₂${\mathrm{CuGaSe}}_2$, efficient electron–hole separation is realized in decomposed phase of this system. (ii) CuIn_1−xZn_0.5xSn_0.5xSe₂${\mathrm{CuIn}}_{1-x}{\mathrm{Zn}}_{0.5x}{\mathrm{Sn}}_{0.5x}{\mathrm{Se}}_2$ has a direct band gap and no impurity state appears in the gap. Therefore, cost reduction is possible by using Zn and Sn instead of In. (iii) n-type CuAl_1−xSn_xS₂${\mathrm{CuAl}}_{1-x}{\mathrm{Sn}}_x{\mathrm{S}}_2$ and p-type Cu_1−xV_CuxAlS₂${\mathrm{Cu}}_{1-x}{\mathrm{V}}_{\mathrm{Cu}x}{\mathrm{AlS}}_2$ have negative activation energy for doped impurities and are expected to be low-resistive transparent conducting sulfides, which should be useful for CuInSe₂${\mathrm{CuInSe}}_2$-based PVSCs.     

First-principles study of the magnetic properties of nitrogen-doped alkaline earth metal oxides

We present a first-principles study of the magnetic properties of N-doped MgO, CaO and SrO, which have been proposed to constitute a new class of dilute magnetic semiconductors (DMSs) with no magnetic elements. In this study, it was found that under a homogeneously distributed condition, Curie temperatures could reach room temperature at sufficient N concentrations in the range of 20–30 at.%; however, an inhomogeneous N distribution in these DMSs is the favored configuration, which indicates that spinodal decomposition leads to a room-temperature blocking temperature at smaller N concentrations than those estimated for room-temperature ferromagnetism in the homogeneous distribution condition.     

Liquid crystal devices for optical communication and information processing systems

This paper reviews liquid crystal optical devices including tunable filters, photonic switches and spatial light modulators, and examines their application to optical communication and information processing systems. Optical processing has three major advantages: massive parallelism, high speed and broad wavebands. Compared with typical optical materials including silica, semiconductors and inorganic electrooptic crystals used in communication systems, a liquid crystal has a number of outstanding features including its large refractive index change and large polarization rotation power at a low voltage. These features make it possible to develop new optical components.     

The relation between lattice-parameter and particle size in ZnS:Cu Phosphor

The effect of particle size on life time in electroluminescent phosphor was investigated using fractionated samples. The life time of large-particle size phosphors was longer than that of small-particle size phosphor. It was found that particle size has a close relation with the lattice-parameter magnitude; the lattice parameter was larger in a small-particle size phosphor when the activator and coactivator content were the same. It was concluded that the lattice parameter was an important brightness life-time factor.     

Ajugamarin,a new bitter diterpene from ajuga nipponensis makino

The structure of a new bitter neo-clerodane, ajugamarin, isolated from $\text{Ajuga nipponensis}$ Makino, has been elucidated by spectroscopic studies and confirmed by X-ray crystallographic analysis.     

Synthesis of some 10-alkyl-5-deazaflavins and their use in the oxidation of benzyl alcohol and benzylamine

A series of 3-methyl- and 3-phenyl-10-alkyl-5-deazaflavins were synthesized in order to examine whether the length of 10-alkyl-substituents influences the oxidizing power.     

Electronic structure of ferrocyanide ion calculated by the SCF Xα-scattered wave generalized partitioning method

A generalized partitioning (GP) version of the Xα scattered-wave (SW) method is used to carry out self-consistent calculations of the electronic states for the ferrocyanide ion. The GP scheme is based on a generalization of the standard muffin-tin partitioning of the molecular space in which the neighboring atomic regions are maintained into local clusters. The calculated energy spectrum leads to interpretation for the X-ray photoelectron emission and optical transitions for the ion in fairly good agreement with the experimental results. It is concluded that the self-consistent GP scheme offers very good possibilities to improve the physical realism of the SW theory for a wide range of open structures.     

Synthesis of thiosaccharides employing the Pummerer rearrangement of tetrahydrothiopyran oxides

The Pummerer rearrangement of 1-deoxy-5-thioglucopyranose derivatives carrying acetonides at the C3,4-positions proceeded regioselectively at the C1 position by treating with TFAA in the presence of pyridine. Studies employing deuterium-labelled derivatives revealed that the reaction was induced by E2 1,2-elimination of trifluoroacetic acid of the trifluoroacetoxy sulfonium intermediate. This methodology was applied to the synthesis of an isomaltotriose derivative consisting of 5-thioglucopyranoside units.     

Positron lifetimes and distributions in the infinite-layer compound SrCuO2 and related materials

We have calculated distributions and lifetimes of positrons in the infinite-layer compound SrCuO₂ and those trapped at possible point defects therein. In the delocalized state, positrons show their density maxima at interstitial sites in the Sr planes and have a significant overlap also with Cu and O atoms. The corresponding positron lifetime is 149 ps. It has been revealed that the Sr vacancy strongly localizes positrons with the binding energy of 2.8 eV and the lifetime of 238 ps, while the O vacancy does not trap positrons. Calculations are also performed on related materials Sr₂Cu₄O₆ and Sr₄Cu₆O₁₀, which are characterized by one-dimensional networks of edge-sharing CuO₄ squares. Positrons are predominantly distributed between these networks in these materials and their corresponding lifetimes are 170–171 ps.