Donor−acceptor pair luminescence in compensated Si for solar cells

A broad band with a fine structure on the higher energy side has been commonly observed in photoluminescence at 4.2 K from compensated Si for solar cells involving P donors and B acceptors on the order of 1016 cm⁻³. We calculated the theoretical spectrum of donor−acceptor (DA) pair luminescence from the density distribution of pairs as a function of the transition energy of respective pairs with separations ranging from 1.9 to 3.3 nm. A close agreement was obtained between the observed spectral structure and the theoretical curve using the generally accepted P donor and B acceptor ionizationenergies, where a systematic deviation was explained by the Van der Waals interaction between shallow P donors and B acceptors. This allows us to conclude that the band with the fine structure is due to the P-donor−B-acceptor pair recombination. This identification was confirmed by the observation of As-donor−B-acceptor pair luminescence in an As-doped sample. The present findings indicate that P and B impurities with concentrations on the order of 1016 cm⁻³ are unlikely to form complexes and that their ionizationenergies are not changed from those in the low concentration range.This work was partly supported by the New Energy and Industrial Technology Development Organization (NEDO) under the Ministry of Economy, Trade and Industry (METI)

Efficient generation of an oxidopyrylium ylide using a Pd catalyst and its [5+2] cycloadditions with several dipolarophiles

An efficient method for the generation of an oxidopyrylium ylide from 6-acetoxy-6-acetoxymethyl-2H-pyran-3(6H)-one using a Pd catalyst and [5+2] cycloadditions of the resulting ylide are described. Among substituted styrene derivatives as dipolarophiles, electron-rich styrenes showed higher yield (up to 80%). The [5+2] cycloaddition reactions can also be applied to exo-methylene cyclic compounds, and an improved method for the synthesis of polygalolide intermediate has been demonstrated.ArticleCHEMICAL COMMUNICATIONS.54(9):1109-1112(2018)journal articl

Characteristic expression of twelve rice PR1 family genes in response to pathogen infection, wounding, and defense-related signal compounds (121/180)

Pathogenesis-related (PR) proteins have been used as markers of plant defense responses, and are classified into 17 families. However, precise information on the majority members in specific PR families is still limited. We were interested in the individual characteristics of rice PR1 family genes, and selected 12 putatively active genes using rice genome databases for expressed genes. All were upregulated upon compatible and/or incompatible rice-blast fungus interactions; three were upregulated in the early infection period and four in the late infection period. Upon compatible rice–bacterial blight interaction, four genes were upregulated, six were not affected, and one was downregulated. These results are in striking contrast to those among 22 ArabidopsisPR1 genes where only one gene was pathogen-inducible. The responses of individual genes to salicylic acid, jasmonic acid, and ethylene induced defense signaling pathways in rice are likely to be different from those in dicot plants. Transcript levels in healthy leaves, roots, and flowers varied according to each gene. Analysis of the partially overlapping expression patterns of rice PR1 genes in healthy tissues and in response to pathogens and other stresses would be useful to understand their possible functions and for use as characteristic markers for defense-related studies in rice