Electrolytes for Dye-Sensitized Solar Cells Based on Interhalogen Ionic Salts and Liquids

Dye-sensitized solar cells strike back

Dye-sensitized solar cells (DSCs) are celebrating their 30th birthday and they are attracting a wealth of research efforts aimed at unleashing their full potential. In recent years, DSCs and dye-sensitized photoelectrochemical cells (DSPECs) have experienced a renaissance as the best technology for several niche applications that take advantage of DSCs' unique combination of properties: at low cost, they are composed of non-toxic materials, are colorful, transparent, and very efficient in low light conditions. This review summarizes the advancements in the field over the last decade, encompassing all aspects of the DSC technology: theoretical studies, characterization techniques, materials, applications as solar cells and as drivers for the synthesis of solar fuels, and commercialization efforts from various companies.

Ionic-liquid-assisted synthesis of the phosphorus interhalides [PBr4][IBr2] and [PBr4][I5Br7]

Ionic-liquid based synthesis results in the phosphorus interhalides [PBr₄][IBr₂] and [PBr₄]₂[I₅Br₇] whereof the latter shows thermal halogen release of 96.8 wt% (≤300 °C).

Electrolytes based on alkoxysilyl-functionalized ionic liquids: viscoelastic properties and conductivity

Ionic liquids can be successfully used as electrolytes in electrochemical devices when they are in their quasi-solid state. Among several methods of solidification, a sol-gel process was chosen and a set of alkoxysilyl-functionalized iodide imidazolium-based ionic liquids were synthesized. The electrolytes were prepared by mixing these ionic liquids with a non-polymerisable ionic liquid (1-methyl-3-propylimidazolium iodide (MPIm(+)I(-))). Iodine was dissolved in an electrolyte matrix in order to form an I3(-)/I(-) redox couple. The change of the structure from sol to gel was followed by rheological tests in order to show the effect of different rheological parameters on the gelation process. The solvolysis with glacial acetic acid and condensation were followed by rheological experiments on the samples taken from a batch, and in situ on the rheometer. The formed three-dimensional sol-gel networks of various alkoxysilyl-functionalized ionic liquids differed in their microstructures and viscoelastic properties that were correlated with conductivity. The results show that the conductivity of approximately 10(-3) S cm(-1) at room temperature was achieved for the gels with relatively high values of elastic modulus and noticeable viscous contribution. It is shown that not only the viscosity but also the viscoelastic behavior and especially the relationship between viscous and elastic moduli (phase shift) together with the time of gelation are essential for the high conductivity of electrolytes.

Electrochemical synthesis of indium(0) nanoparticles in haloindate(III) ionic liquids

A synthetic route to indium(0) nanoparticles via an electrochemical reduction of haloindate(III) ionic liquids to indium(I), and its subsequent disproportionation to indium(0) and indium(III) in the bulk electrolyte, is described. In this sustainable method, the ionic liquid acts simultaneously as metal source, templating agent, and stabilising agent, with the electron as the only reducing agent. The nature of the ionic liquid cation is demonstrated to strongly affect the morphology and size distribution of the indium(0) nanoparticles.

Benzimidazolyl functionalized ionic liquids as an additive for high performance dye-sensitized solar cells

Benzimidazolyl functionalized ionic liquids were synthesized and applied as additives for dye-sensitized solar cells. The fabricated devices show an overall power conversion efficiency of ~7.79% under AM 1.5 radiation (50 mW cm(-2)), and an excellent long-term stability.

Liquid electrolytes for dye-sensitized solar cells

The present review offers a survey of liquid electrolytes used in dye-sensitized solar cells from the beginning of photoelectrochemical cell research. It handles both the solvents employed, and the prerequisites identified for an ideal liquid solvent, as well as the various effects of electrolyte solutes in terms of redox systems and additives. The conclusions of the present review call for more detailed molecular insight into the electrolyte-electrode interface reactions and structures.

Structural Characterization of Novel Ionic Salts Incorporating Trihalide Anions

The crystal structures of several low-melting salts containing trihalide ions, namely 1-ethyl-3-methylimidazolium tribromide ([C2mim][Br3]), 1-ethyl-1-methylpyrrolidinium tribromide ([C2mpyr][Br3]), and 1-propyl-1-methylpyrrolidinium triiodide ([C3mpyr][I3]), are reported for the first time. Thermal analysis reveals that the tribromide salts are lower-melting than their monohalide analogues. Analysis of the crystal structures allows examination of the influence of the anions on the physical properties of the salts.

Radial electron collection in dye-sensitized solar cells

We introduce a new photoelectrode architecture consisting of concentric conducting and semiconducting nanotubes for use in dye-sensitized solar cells (DSSCs). Atomic layer deposition is employed to grow indium tin oxide (ITO) within a porous template and subsequently coat the high area photoelectrode with amorphous TiO 2. Compared with control devices lacking a current collector within the pores, the new photoelectrode geometry exhibits dramatically higher current densities, an effect attributed to the radial collection of electrons.