Coupling of Zinc Porphyrin Dyes and Copper Electrolytes: A Springboard for Novel Sustainable Dye-Sensitized Solar Cells.

The combination of ß-substituted Zn2+ porphyrin dyes and copper-based electrolytes represents a sustainable route for economic and environmentally friendly dye-sensitized solar cells. Remarkably, a new copper electrolyte, [Cu(2-mesityl-1,10-phenanthroline)2]+/2+, exceeds the performance reached by Co2+/3+ and I-/I3- reference electrolytes.

Electronic and charge transfer properties of bio-inspired flavylium ions for applications in TiO2-based dye-sensitized solar cells.

We present here a complete study on four synthetic environmentally friendly flavylium salts employed as sensitizers for dye-sensitized solar cells (DSSCs). The effect of several donor groups on the molecular structure of flavylium ions was investigated by combining electrochemical, spectroscopic and computational means. The computational investigation indicated that these molecules can interact strongly with the TiO2 surface by a single OH group of the dihydroxybenzene moiety, and can efficiently inject electrons into the TiO2 following the excitation of their lowest singlet states exhibiting charge transfer (CT) character. In general, all dyes within the explored series exhibited quite good regeneration efficiencies, often ≥70%, in the presence of an iodide electron donor, explaining the high IPCEs and photocurrents recorded in the presence of high lithium content electrolytes. The combination of molecular orbital calculations and electrochemical measurements has also revealed that the introduction of donor groups on the benzopyrylium ring has a generally positive effect resulting in an extended low energy light harvesting and in a potential improvement of the photoinduced charge separation at the semiconductor/dye/electrolyte interface. It also increases the reversibility of the oxidative redox processes of these bio-inspired species, a feature in favour of their long-term stability. At present the best dye within the explored series is 7-(N,N-diethylamino)-3',4'-dihydroxyflavylium chloride based on a dialkylamine donor which is capable of delivering, under optimized conditions, a short-circuit current density of 15 mA cm-2. This is the highest value so far obtained for synthetic analogues of anthocyanins.

Rapid Static Sensitizer Regeneration Enabled by Ion Pairing.

An anionic CoII complex, [Co(TTT) (NCS)3]- (TTT = 4,4',4″-tri-tert-butyl-2,2':6',2″-terpyridine and NCS = isothiocyanate), was synthesized for use in dye-sensitized solar cells (DSSCs). The CoII complex was found to ion-pair with the hexacationic sensitizer [Ru(tmam)2(dcb)]6+ (tmam = 4,4'-bis(trimethylaminomethyl)-2,2'-bipyridine and dcb = 4,4'-(CO2H)2-2,2'-bipyridine) anchored to TiO2 thin films immersed in acetonitrile solution. Visible light excitation of the ion pairs resulted in excited-state injection followed by rapid static regeneration of the oxidized sensitizer (<10 ns). The static component to regeneration gave an ion-pair equilibrium constant of 6000 M-1. This value is an order of magnitude smaller than the equilibrium constant determined for [Ru(tmam)2(deeb)]6+ (deeb = 4,4'-(CO2Et)2-2,2'-bipyridine) dissolved in acetonitrile. DSSC studies employing [Co(TTT) (NCS)3]- or the cationic [Co(DTB)3]2+ (DTB = 4,4'-di-tert-butyl-2,2'-bipyridine) as redox mediators revealed a 3 fold photocurrent increase in the presence of the anionic cobalt complex. As the regeneration step was greatly enhanced through the formation of Coulombic ion pairs, both electron injection and regeneration were complete within 10 ns which is unprecedented for dye-sensitization. The results obtained reveal that ground-state ion-pairing can be a powerful strategy for DSSC optimization.

Correction: On the stability of manganese tris(ß-diketonate) complexes as redox mediators in DSSCs.

Correction for 'On the stability of manganese tris(ß-diketonate) complexes as redox mediators in DSSCs' by Stefano Carli et al., Phys. Chem. Chem. Phys., 2016, 18, 5949-5956.

Single Walled Carbon Nanohorns as Catalytic Counter Electrodes for Co(III)/(II) Electron Mediators in Dye Sensitized Cells.

The electrochemical properties of both pristine single walled carbon nanohorns (SWCNHS) and their chemically oxidized form (ox-SWCNHS) spray coated onto fluorine doped SnO2 (FTO) were investigated in the framework of the fabrication of cobalt based transparent dye sensitized solar cells (DSSCs). These new nanocarbon substrates, evaluated in conjunction with the Co(bpy)3(2+/3+) (bpy = 2,2'-bipyridine) redox mediator, are endowed with excellent electrocatalytic properties, ease of fabrication, and very promising stability and display a great potential for replacing the best noble metal and conductive polymer catalytic materials in the building of semitransparent counter electrodes in new generation photoelectrochemical devices.

On the stability of manganese tris(ß-diketonate) complexes as redox mediators in DSSCs.

The photoelectrochemical properties and stability of dye sensitized solar cells containing Mn(ß-diketonato)3 complexes, [Mn(III)(acac)3] () (acac = acetylacetonate), [Mn(III)(CF2)3] () (CF2 = 4,4-difluoro-1-phenylbutanate-1,3-dione), [Mn(III)(DBM)3] () (DBM = dibenzoylmethanate), [Mn(II)(CF2)3]TBA (TBA = tetrabutylammonium) () and [Mn(II)(DBM)3]TBA (), have been evaluated. At room temperature, the complexes undergo ligand exchange with 4-tert-butyl-pyridine, an additive commonly used in the solar device to reduce charge recombination at the photoanode. An increased device stability was achieved by using the Z907 dye and passivating the photoanode with short chain siloxanes. It was also found that the Mn(ii)/(iii) couple is involved in the dye regeneration process, instead of Mn(iii)/(iv) (E1/2 > 1 V vs. SCE) previously indicated in the literature.