Electronic Tuning of Nickel-Based Bis(dicarbollide) Redox Shuttles in Dye-Sensitized Solar Cells

Carboranylphosphines: B9-Substituted Derivatives with Enhanced Reactivity for the Anchoring to Dendrimers

Several ortho-carboranes bearing a phenoxy or a phenylamino group in the B9 position were prepared employing various protection and deprotection strategies. Following established protocols, dendritic compounds were synthesized from a hexachlorocyclotriphosphazene or thiophosphoryl chloride core, and possible anchoring options for the B9-substituted ortho-carboranes were investigated experimentally and theoretically (DFT). Furthermore, 1- or 1,2-phosphanyl-substituted carborane derivatives were obtained. The resulting diethyl-, diisopropyl-, di-tert-butyl-, diphenyl- or diethoxyphosphines bearing a tunable ortho-carborane moiety are intriguing ligands for future applications in homogeneous catalysis or the medicinal sector.

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.

Redox Active Compounds in Controlled Radical Polymerization and Dye-Sensitized Solar Cells: Mutual Solutions to Disparate Problems

Controlled radical polymerization (CRP) and dye-sensitized solar cells (DSSCs) are two fields of research that at an initial glance appear to have little in common. However, despite their obvious differences, both in application and in scientific nature, a closer look reveals a striking similarity between many of the compounds widely used as control agents in radical polymerization and as redox couples in dye-sensitized solar cells. Herein, we review the various redox active compounds used and examine the characteristics that give them the ability to perform this dual function. In addition we explore the advances in the understanding of the structural features that enhance their activity in both CRP and DSSCs. It is hoped that such a comparison will be conducive to improving process performance in both fields.

Dyes and Redox Couples with Matched Energy Levels: Elimination of the Dye-Regeneration Energy Loss in Dye-Sensitized Solar Cells

In dye-sensitized solar cells (DSSCs), a significant dye-regeneration force (ΔG(reg)(0)≥0.5 eV) is usually required for effective dye regeneration, which results in a major energy loss and limits the energy-conversion efficiency of state-of-art DSSCs. We demonstrate that when dye molecules and redox couples that possess similar conjugated ligands are used, efficient dye regeneration occurs with zero or close-to-zero driving force. By using Ru(dcbpy)(bpy)2(2+) as the dye and Ru(bpy)2(MeIm)2(3+//2+) as the redox couple, a short-circuit current (J(sc)) of 4 mA cm(-2) and an open-circuit voltage (V(oc)) of 0.9 V were obtained with a ΔG(reg)(0) of 0.07 eV. The same was observed for the N3 dye and Ru(bpy)2(SCN)2(1+/0) (ΔG(reg)(0)=0.0 eV), which produced an J(sc) of 2.5 mA cm(-2) and V(oc) of 0.6 V. Charge recombination occurs at pinholes, limiting the performance of the cells. This proof-of-concept study demonstrates that high V(oc) values can be attained by significantly curtailing the dye-regeneration force.

Iodide-free ionic liquid with dual redox couples for dye-sensitized solar cells with high open-circuit voltage

A novel ionic-liquid mediator, 1-butyl-3-{2-oxo-2-[(2,2,6,6-tetramethylpiperidin-4-yl)amino]ethyl}-1H-imidazol-3-ium selenocyanate (ITSeCN), has been successfully synthesized for dye-sensitized solar cells (DSSCs). ITSeCN possesses dual redox channels, imidazolium-functionalized 2,2,6,6-tetramethylpiperidine N-oxyl (TEMPO) and selenocyanate, which can serve as the cationic redox mediator and the anionic redox mediator, respectively. Therefore, ITSeCN has a favorable redox nature, which results in a more positive standard potential, larger diffusivity, and better kinetic heterogeneous rate constant than those of iodide. The DSSC with the ITSeCN electrolyte shows an efficiency of 8.38 % with a high open-current voltage (VOC ) of 854.3 mV, and this VOC value is about 150 mV higher than that for the iodide-based DSSC. Moreover, different electrocatalytic materials were employed to trigger the redox reaction of ITSeCN. The ITSeCN-based DSSC with the CoSe counter electrode achieved the best performance of 9.01 %, which suggested that transition-metal compound-type materials would be suitable for our newly synthesized ITSeCN mediator.

Transition metal complex redox shuttles for dye-sensitized solar cells

This review provides an in-depth investigation into exciting alternative electrolyte shuttles in DSSCs and the various advantages that they provide, such as high conversion efficiency and non-corrosive properties.

Thiocyanate-free ruthenium(II) sensitizers for dye-sensitized solar cells based on the cobalt redox couple

Two thiocyanate-free ruthenium(II) sensitizers, TFRS-41 and TFRS-42, with distinctive dialkoxyphenyl thienyl substituents were successfully prepared and tested for potential applications in making dye-sensitized solar cells (DSCs). Subsequent device fabrication was conducted by using a [Co(bpy)3 ](2+/3+) -based (bpy=2,2'-bipyridine) electrolyte, for which the best performance data, namely, JSC =13.11 mA cm(-2) , VOC =862 mV, fill factor=0.771, and η=8.71%, were recorded for the sensitizer TFRS-42 with a 2,6-dialkoxyphenyl substituent under AM 1.5G irradiation. The markedly higher Voc value was confirmed by the longer electron lifetime revealed in transient photovoltage (TPV) measurements versus the TFRS-1 sensitizer. In addition, DFT calculation and detailed first-principles computational analysis were conducted to provide a rationale for the observed trends in their photovoltaic performances and electron lifetimes, with reference to different performances exhibited by three thiocyanate-free sensitizers, TFRS-1, TFRS-41 and TFRS-42, versus Z907 reference. Through the proper control of peripheral substituents, the thiocyanate-free ruthenium(II)-based DSC sensitizers can positively influence the performances of DSCs, with better light-harvesting capability and suppressed charge recombination, for DSC cells fabricated by using a [Co(bpy)3 ](2+/3+) -based electrolyte.

Efficient dye-sensitized solar cells using a tetramethylthiourea redox mediator

An organic redox couple tetramethylthiourea/tetramethylformaminium disulfide (TMTU/TMFDS(2+) ) is evaluated in dye-sensitized solar cells in conjunction with a series of indoline and ruthenium-based dyes. Of these, devices with indoline dye D205 show the best performance, with an optimized power conversion efficiency of 7.6 % under AM 1.5G 1 sun illumination. Charge collection and injection are highly efficient in all TMTU-based DSCs studied. Regeneration of indoline dyes is highly efficient, whereas regeneration of ruthenium dyes by TMTU is less efficient, accounting for their inferior performance. Impedance spectroscopy results reveal that using an optimized TMTU/TMFDS(2+) electrolyte solution, the TiO2 conduction band edge is 300-400 meV lower than when an optimized I3 (-) /I(-) electrolyte is used. The would-be loss in open-circuit voltage caused by the downward conduction band shift is mostly compensated by approximately the 200 meV lower redox level of the TMTU/TMFDS(2+) electrolyte and up to 1000 times slower recombination rates. This makes TMTU/TMFDS(2+) a promising redox couple in the development of highly efficient solar energy conversion devices.