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A series of tri- tert-butyl zinc(II) phthalocyanines (Pcs) substituted with pyridyl, carboxyl, or picolinic acid anchoring groups on the periphery were prepared. Photovoltaic (PV) studies on these dyes were carried out revealing some interesting features. In the case of the pyridyl-substituted Pcs, the PV properties were found to depend strongly on the the pyridyl substitution pattern ( meta or para) and the number of pyridyl units at the macrocycle's periphery (one or two). For these four pyridyl-substituted Pcs, higher photovoltaic efficiencies were obtained for 1) the para- versus the meta-substituted Pcs, and 2) the mono- versus the bis-functionalized dyes. In order to improve the poor adsorption of the pyridyl-substituted Pcs onto TiO2, a new dye was tested bearing a picolinic acid unit. This moiety combines a carboxylic acid function, as a strong anchoring group for binding to TiO2, with an electron-withdrawing nitrogen atom for better electron injection into the semiconductor's conduction band. For this latter system, an improvement in the PV efficiency up to 2.1 % was obtained. [ABSTRACT FROM AUTHOR]

The detailed synthesis and characterization of four ruthenium(II) complexes [RuLL′(NCS)2] is reported, in which L represents a 2,2′-bipyridine ligand functionalized at the 4,4′ positions with benzo[1,2- b:4,5- b′]dithiophene derivatives (BDT) and L′ is 2,2′-bipyridine-4,4′-dicarboxylic acid unit (dcbpy) (NCS=isothiocyanate). The reaction conditions were adapted and optimized for the preparation of these amphiphilic complexes with a strong lipophilic character. The photovoltaic performances of these complexes were tested in TiO2 dye-sensitized solar cell (DSSC) achieving efficiencies in the range of 3-4.5 % under simulated one sun illumination (AM1.5G). [ABSTRACT FROM AUTHOR]

Two ruthenium sensitizers TT-230 and TT-232 based on cyclopenta[2,1-b:3,4-b′]dithiophene (CDT) were tested in dye-sensitized solar cells (DSSCs) using a tri-iodide/iodide redox couple, and their performances compared to the benchmark Z907 . Both dyes of general formula Ru(LL′)(NCS) 2 feature the same 4,4′-dicarboxylic acid 2,2′-bipyridine moiety acting as the anchoring group (L) to attach the dye on the TiO 2 surface, and two CDT subunits as ancillary groups (L′) either directly-linked ( TT-230) or vinylene-linked ( TT-232 ) to the bipyridine moiety. In comparison with TT-230 , the π-extended conjugation in TT-232 caused significant redshift and broadening of the absorption bands. However, despite better light-harvesting properties, the DSSC device sensitized with TT-232 strikingly underperformed compared to TT-230 under same conditions (PCE = 3.2% and 6.1%, respectively). The use of co-adsorbent (CHENO) or surfactants did not help to improve the photovoltaic properties of TT-230 , and resulted in a degradation of the overall efficiency of the cell. [ABSTRACT FROM AUTHOR]