Why does the open-circuit voltage in a micro-crystalline silicon PIN solar cell decrease with increasing crystalline volume fraction?

In hydrogenated micro-crystalline silicon (μc-Si:H) thin film solar cells, the open-circuit voltage (V_OC) shows a decline when the crystalline volume fraction (F_c) of the intrinsic μc-Si:H layer increases from 60% to over 90%. In this article we have simulated the experimental characteristics of solar cells, having intrinsic layers of different degrees of crystallinity to understand the reasons why. In order to model all aspects of the characteristics, we had to assume (a) wider band tails, (b) a higher mid-gap defect density and (c) a lower band gap for the more crystallized material. Modeling reveals that all three factors lower the field in the volume of the device and hence V_OC, due to higher photo-generated hole-trapping close to the P/I interface. The third factor brings the quasi-Fermi levels closer to the band-edges, resulting in higher free and trapped carrier densities throughout the device, with the trapped hole population particularly high at the P/I interface. We further show that V_OC is higher in a crystalline silicon PN cell, in spite of a sharply reduced band gap, because the lower effective density of states at the band-edges and sharply reduced band gap defect density overcome the effect of the smaller band gap.     

Organylthiochloroacetylenes: IV. Reaction with Thiourea

Alkylthiochloroacetylenes react with thiourea in acetone to form S-(alkylthioethynyl)isothiuronium chlorides and N-[1-(alkylthio)ethylidene]thioureas; phenylthiochloroacetylene reacts with thiourea to give 4-(phenylthio)-2-imino-1,3(3H)-thiazole hydrochloride.     

Metal Complexes of Phthalocyanine Structural Analogs with Oxygen- or Nitrogen-containing Heterorings. Synthesis and Properties

Nucleophilic substitution of the bromine atom and nitro group in 4-bromo-5-nitrophthalodinitrile and reduction of 4-benzoylamino-5-nitrophthalodinitrile gave, respectively, tribenzo[b,e,g][1,4]dioxocine-7,8-dicarbonitrile and 2-phenylbenzimidazole-5,6-dicarbonitrile. These compounds were used to synthesize new structural analogs of phthalocyanine, having oxygen- and nitrogen-containing heterorings, (tetratribenzo[b,e,g][1,4]dioxocino[7,8-b,g,l,q]-5,10,15,20-tetraazaporphyrinato)copper(II) and (23,73,123,173-tetraphenyl-tetrabenzimidazolo[5,6-b,g,l,q]-5,10,15,20-tetraazaporphyrinato)cobalt(II). Spectral properties of the resulting complexes were studied.     

Nucleophilic substitution in 4-bromo-5-nitrophthalodinitrile: XI. Preparation,properties, and prediction of mesomorphism in mixed-substituted phthalocyanines containing aryloxy and benzotriazole fragments

Stepwise nucleophilic substitution of bromine and nitro group in 4-bromo-5-nitrophthalodinitrile has led to a series of phthalonitriles containing benzotriazole and aryloxy fragments; basing on them, the mixed-substituted phthalocyanines have been prepared. The spectral properties of products have been studied. According to simulation of columnar mesomorphism only one of the products is not capable of mesomorphism characteristic of discotic mesogens; the result has been confirmed with the experiment.     

Synthesis and properties of magnetite-poly(aminopropylsiloxane) composites

A method is developed for the synthesis of nanosized Fe₃O₄-(SiO₂) _x [NH₂(CH₂)₃SiO_3/2] _y magnetic composites with varied SiO₂: NH₂(CH₂)₃SiO_3/2, weight/weight, ratios. The structure, texture, morphology, and magnetic properties of the obtained materials are studied by several physicochemical methods. It is shown that the composites represent systems of magnetite nanoparticles coated with poly(aminopropylsiloxane). The specific surface areas, pore volumes, and saturation magnetizations of the composites are in the ranges of 21–27 m²/g, 0.03–0.04 cm³/g, and 59–62 G cm³/g, respectively.     

Branched-chain nature of hydrogen combustion in the detonation mode

Minor admixtures of the simplest hydrocarbons can prevent detonation and break down a steady-state detonation wave in hydrogen-air mixtures at atmospheric and higher pressures. Therefore, the determining role in the appearance and propagation of the detonation wave is played by the branched mechanism and, accordingly, by the competing chain branching and termination reactions. Without taking into account these reactions, combustion theory cannot explain the basic regularities of the process, including the concentration limits of detonation.     

Synthesis and investigation of the properties of α-(6-methyl-2-benzothiazolyl)-α-phenyl-β-(2,6-dinitrophenyl)hydrazyl, α-(2-methyl-6-benzothiazolyl)-α-phenyl-β-(2,6-dinitrophenyl)-hydrazyl,and the correspondinghydrazines

-(6-Methyl-2-benzothiazolyl)--phenyl--(2,6-dinitrophenyl)hydrazyl and -(2-methyl-6-benzothiazolyl)--phenyl--(2,6-dinitrophenyl)hydrazyl and their corresponding hydrazines were synthesized. The properties of the compounds obtained were investigated by IR, UV, and visible spectroscopy. Their complexing ability was studied by an optical method and from their electrical conductivity. The ESR spectra of the radicals were recorded. The limiting currents and reduction potentials of the hydrazines on a dropping mercury electrode were found. The charge and spin densities of the compounds were calculated by means of the Hückel MO and MacLachlan methods. It was demonstrated that the hydrazines form unstable charge-transfer complexes in benzene—piperidine solutions; the characteristics of these complexes depend on the structure of the RRN-NH-hydrazine residue.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1484–1490, November, 1971.     

Characteristics of a localized gas discharge

The rf capacitive gas discharge with an interelectrode distance of 15–200 µm is studied, and possible forms of its existence are established. The conditions for the formation of discrete microdischarges with a preset geometry, which are localized near some elements of the surfaces of the electrodes, are formulated.     

Use of a fluorine-containing solvent in the synthesis of YBa<Subscript>2</Subscript>Cu<Subscript>3</Subscript>O<Subscript>7 − δ</Subscript> single crystals

A laboratory technological procedure has been developed for the synthesis of high-temperature superconducting YBa₂Cu₃O_{7 ? δ} single crystals (T _c ～ 90 K, ΔT _c ～ 1.0 K) up to 0.25 cm² in size from a nonstoichiometric fluorine-containing flux of (YO_1.5)(BaO)_{4 ? x}(BaF₂)_x(CuO)₁₀, where 2 ≥ x ≥ 0, using a combination of enhanced nucleation and directional crystallization by the Czochralski method. Studies using differential thermal analysis demonstrated that the addition of BaF₂ decreased the eutectic-crystallization temperature and increased the crystal-growth rate. The optimum concentration of BaF₂ in the starting melt composition was found (x = 0.2). The single-crystal surface was studied by atomic-force nanoscopy. The morphology of single crystals that have been synthesized from a melt of their own components differs substantially from that of crystals grown from a BaF₂-containing melt.     

Interaction of [Mo6Cl14]2− with H2Se: Selective Preparation of [Mo6SeCl13]3−

Reaction of [Mo₆(μ₃-Cl)₈Cl₆]²⁻ with H₂Se, generated in situ from ZnSe and 4 M HCl under hydrothermal conditions lead to the substitution of one or two bridging chlorides, depending on the reagents ratio. With the Mo₆/ZnSe 1:3 molar ratio [Mo₆(μ₃-SeCl₇)Cl₆]³⁻ forms selectively in high yield. Further substitution is more hindered, and even at 1:20 cluster-to-selenide molar ratio a mixture of [Mo₆(μ₃-SeCl₇)Cl₆]³⁻ and [Mo₆(μ₃-Se₂Cl₆)Cl₆]⁴⁻ is formed. The products were characterized by X-ray, Raman spectra and electrospray ionization mass spectrometry.