Dye-sensitized solar cells (DSCs) using ionic liquids, 1-alkyl-3-methylimidazolium iodide (alkyl:  C3−C9), were fabricated with and without a low molecular weight gelator. The highest energy conversion efficiency of 5.0% was obtained from a quasi-solid-state DSC using 1-hexyl-3-methylimidazolium iodide (HMImI). Gelation of these ionic liquids demonstrated better high-temperature durability without decreasing the solar cell efficiency. However, the short-circuit currents (JSC) obtained from these DSCs were about 70% of that obtained from DSCs using organic liquid electrolyte (OLE). To explain the difference of the JSC values between the DSCs using ionic liquid electrolyte (ILE) and OLE, four primitive processes in DSCs, that is, charge transport in the electrolytes, light absorption by I3-, electron diffusion in a TiO2 electrode, and charge recombination, were examined. Viscosities of the ILE decreased with increasing I3- concentration and alkyl chain length. In ILE, measured JSC values increased with incr...

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Photocurrent-determining processes in quasi-solid-state dye-sensitized solar cells using ionic gel electrolytes

Bromination is one of the most important transformations in organic synthesis and can be carried out using bromine and many other bromo compounds. Use of molecular bromine in organic synthesis is well-known. However, due to the hazardous nature of bromine, enormous growth has been witnessed in the past several decades for the development of solid bromine carriers. This review outlines the use of bromine and different bromo-organic compounds in organic synthesis. The applications of bromine, a total of 107 bromo-organic compounds, 11 other brominating agents, and a few natural bromine sources were incorporated. The scope of these reagents for various organic transformations such as bromination, cohalogenation, oxidation, cyclization, ring-opening reactions, substitution, rearrangement, hydrolysis, catalysis, etc. has been described briefly to highlight important aspects of the bromo-organic compounds in organic synthesis.

Use of Bromine and Bromo-Organic Compounds in Organic Synthesis

Electrical oxidation of bis(ethylenedithiolo)tetrathiofulvalene (BEDT-TTF) 1 in a nitrogen saturated tetrahydrofurane solution containing (n-C4H10)4N+I3 as electrolyte results in the deposition of crystal plates of (BEDT-TTF)+ 2I3 (C10H8S8)2I3. These two dimensional crystals are triclinic, space group P1, a = 9.211(2), b=10.850(4), c = 17.488(5) A, α=96.95(2), β = 97.97(2), γ = 90.75(2)°, V = 1717 A3, Mr = 1150.01, Z=2, Dx =2.22 g cm−3. Rw = 0.037 for 2462 observed reflections. Sheets of alternating cations and anions occur in the compound. The most prominent intermolecular S-S contacts (∼3.5A) are found between the stacks of BEDT-TTF. The stacking of the molecules and the interstack contacts give the compound a two-dimensional character which influences the physical properties. The room temperature conductivities in the ab plane range typically between 60 and 250 (ω cm)−1. The conductivity anisotropy in this plane is small with a ratio of σa/σb⩽ 2, while in the direction perpendicular to the ab-...

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Synthesis, Structure and Physical Properties of a Two-Dimensional Organic Metal, Di[bis(ethylenedithiolo)tetrathiofulvalene] triiodide, (BEDT-TTF)+ 2 I− 3

A microporous three-dimensional hydrogen-bonded organic framework (HOF-5) has been constructed from a new organic linker 4,4′,4″,4‴-tetra(2,4-diamino-1,3,5-triazin-6-yl)tetraphenylethene. Activated HOF-5a exhibits a stepwise N2 adsorption isotherm at 77 K, suggesting framework flexibility. The structure of activated HOF-5a has been established by powder X-ray diffraction studies, indicating a significant framework contraction from as-synthesized HOF-5 to activated HOF-5a of ∼21% by volume. HOF-5a shows moderately high porosity with a Brunauer–Emmett–Teller (BET) surface area of 1101 m2/g, and takes up a large amount of acetylene and carbon dioxide under ambient conditions. Powder neutron diffraction studies and theoretical calculations reveal that suitable pore sizes, curvatures, and functional sites collectively enable HOF-5a to encapsulate a high density of carbon dioxide molecules packed in a pseudo-one-dimensional array along the pore channel.

A Flexible Microporous Hydrogen-Bonded Organic Framework for Gas Sorption and Separation

The current status of the long-term stability of dye solar cells (DSCs) and factors affecting it is reviewed. The purpose is to clarify present knowledge of degradation phenomena and factors in these cells by critically separating the assumptions from the solid experimental evidence reported in the literature. Important degradation processes such as dye desorption, decrease in the tri-iodide concentration, degradation at the photoelectrode and counter electrode, affect of ultraviolet light and moisture, and issues related to the sealing, are covered. It is concluded that techniques giving chemical information are needed for the stability investigations of DSCs to reveal possible ways to improve their lifetime. In this regard, experimental methods suitable for separating degradation mechanisms in complete cells during long-term testing are proposed employing specifically designed sealed cell structures, called segmented cells, that provide windows to measure specific cell components without being obscured by the others.

Robert E. Buckles

Papers

Crystal structure of the chlorine complex of bis(p-chlorophenyl) sulfide

The Stability of the Tetramethylammonium Polyiodides in Ethylene Chloride1

Stereospecificity of the Addition of Bromine to cis- and trans-Stilbene1

Spectrophotometric Study of Tetrabutylammonium Tribromide

The Action of Bromine Vapor on Solid Aromatic Compounds1