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Measurements have been made of the variation of the quantum efficiency of electroluminescence as a function of applied field in ZnS:Mn and ZnSe:Mn Schottky diodes. Under very high fields, the quantum efficiency unexpectedly reaches a maximum and then drops. An explanation is proposed which depends on the details of the band structures of ZnS and ZnSe.

The work reported here establishes the existence of $\mathrm{He}_{3}^{}{}_{}{}^{+}$ and $\mathrm{He}_{4}^{}{}_{}{}^{+}$ at room temperature (300\ifmmode^\circ\else\textdegree\fi{}K) in a helium afterglow. The data presented in this paper indicate that the often-measured electron-ion recombination coefficient in 300\ifmmode^\circ\else\textdegree\fi{}K helium afterglows is mainly attributable to electron recombination with $\mathrm{He}_{3}^{}{}_{}{}^{+}$ rather than, as is usually assumed, with the dominant ion $\mathrm{He}_{2}^{}{}_{}{}^{+}$.

In this chapter we treat collision-induced dissociation (CID) within the framework of classical mechanics. Such an approach is of great practical use not only in the calculation of CID cross sections for their own sake, but also in the fields of hot-atom chemistry, high-energy molecular beam reactions, electron recombination and detachment, and charge transfer, where CID, although not the main process of interest, is present alongside other processes and must be properly taken into account. Indeed, CID cannot be treated independently of other product channels, since dissociation competes with these as soon as the collision energy increases beyond the dissociation threshold. A decent CID calculation must treat this competition adequately.

We review the ramifications of non-LTE effects on the determination of nebular properties made by interpreting radio recombination line observations. In particular we focus on the effect that departures from b = 1 and τc << 1 have on the determination of nebular temperatures, and we discuss the effect of impact broadening on the interpretation of radio recombination lines (hydrogen and helium) from inhomogeneous nebulae.

Different excitation mechanisms that have been proposed as responsible for the strength of the Fe II multiplet UV 191 in stellar spectra are discussed. Dielectronic recombination is suggested as an alternative explanation. Some theoretical atomic data are presented.

Herein, the energy level alignment and electron recombination kinetics in solid state dye-sensitized solar cells (DSCs) employing a solid polymer electrolyte (SPE) have been quantitatively characterized. In order to determine the microscopic origin of the enhanced characteristics in polymer electrolytes, we carried out an extensive study of the photovoltaic properties with respect to the electrolyte type and composition, including a liquid electrolyte (LE) and various salt types and concentrations. We observed a smaller downward shift in the conduction band energy of the TiO2 layer upon contact with the SPE as well as a retarded electron recombination rate. These led to an increase in the Voc for DSCs with an SPE, which is mostly attributable to the coordinative interactions of the ethylene oxide (EO) units in poly(ethylene oxide) (PEO) and poly(ethylene glycol) dimethyl ether (PEGDME) with metallic Li+ ions and Ti atoms. Such coordinative interactions induce 1) the capture of Li+ cations in the bulk of the polymer electrolyte, thereby reducing their effective concentration and 2) the facile formation of a PEO passivation layer on top of the TiO2 layer. Therefore, it was concluded that the high Voc in solid state DSCs employing a polymer electrolyte is attributable to the coordinative properties of the EO units in PEO and PEGDME in the SPE. This work was financially supported by the Korea Center for Artificial Photosynthesis (KCAP) (Number 2009-0093883). This project was funded by the Deanship of Scientific Research (DSR) at King Abdulaziz University, under Grant No HiCi/2-130-36. Therefore, the authors acknowledge and thank the KCAP and DSR for technical and financial support. S.D.G.

Mesoporous TiO2 nanoparticle films are used as photoanodes for high efficiency dye-sensitized solar cells (DSC). In spite of excellent photovoltaic power conversion efficiencies (PCE) displayed by titanium dioxide nanoparticle structures, the transport rate of electrons is known to be low due to low electron mobility. So the alternate oxides including ZnO, that possesses high electron mobility, are being investigated as a potential candidate for photoanodes. However, the PCE with ZnO is still lower than TiO2 and this is typically attributed to the low internal surface area. In this work, we attempt to make a one-to-one comparison of the photovoltaic performance and the electron transfer dynamics involved in DSC, with ZnO and TiO2 as photoanodes. Previously such comparative investigations were hampered due to the morphological differences (internal surface area, pore diameter, porosity) that exist between zinc oxide and titanium dioxide films. We circumvent this issue by depositing different thickness of these oxides, by atomic layer deposition (ALD), on an arbitrary mesoporous insulating template and subsequently used them as photoanodes. Our results reveal that at an optimal thickness, ZnO exhibits photovoltaic performances similar to TiO2, but the internal electron transfer properties differ. The higher photogenerated electron transport rate contributed to the performances of ZnO but in the case of TiO2, it’s the low recombination rate, dye loading and fast electron injection.

Herein, we present the first use of a gallium oxide tunnelling layer to significantly reduce electron recombination in dye-sensitized solar cells (DSC). The sub-nanometer coating is achieved using atomic layer deposition (ALD) and leading to a new DSC record open-circuit potential of 1.1V with state-of-the-art organic D-π-A sensitizer and cobalt redox mediator. After ALD of only a few angstroms of Ga2O3, the electron back reaction is reduced by more than an order of magnitude while charge collection efficiency and fill factor are increased by 30% and 15% respectively. The photo-generated exciton separation processes of electron injection into the TiO2 conduction band and the hole injection into the electrolyte are characterized in detail.

The present invention provides a porous semiconductor electrode passivated by way of a layer applied by an atomic layer deposition (ALD) process. The semiconductor electrode can be advantageously used in dye-sensitized solar cells (DSCs) having increase open current voltages (Voc). By selecting the thickness and the material of the passivating or blocking layer, high Voc without substantial reduction of short circuit current (JSC) is achieved, thereby resulting in devices exhibiting excellent power conversion efficiencies.

We propose a mechanism whereby electron capture by neutral donors can become significant in electron recombination in n-type semiconductors at liquid helium temperatures.

The absolute cross-sections, (Q), for the charge-exchange between positive ions of known electron recombination energies (eVi) and the neutral molecules CCl4, CHCl3, CH2Cl2, CH3Cl and HCl have been determined. The cross-sections are independent of the kinetic energy of the primary ions within the range studied. A plot of Q against eVi for each secondary ion constitutes a charge-exchange mass spectrum (CEMS) from which appearance potentials of the secondary ions have been determined: CCl+3(from CCl4), 11.75 ± 0.2 eV; CHCl+2(from CHCl3), 11.5 ± 0.2 eV; CH2Cl+2(from CH2Cl2), 11.3 ± 0.2 eV; CH2Cl+(from CH2Cl2), 11.9 ± 0.2 eV. The CEMS are compared with the corresponding photoelectron spectra.

La recherche du radical HCCO interstellaire a permis de placer des limites superieures de HCCO/H 2 CCO

The absolute cross-sections, Q, for the charge exchange in the gas phase between twenty eight primary positive ions of known electron recombination energy, E, and three isomeric esters, ethyl acetate, methyl proprionate and propyl formate, have been measured. A plot of Q against E for a particular product ion constitutes a charge-exchange mass spectrum, c.e.m.s., from which the product ion's appearance potential is directly obtained. The appearance potentials of the three esters and eleven of their principle ionic fragments are reported.