Page - 31 - in Photovoltaic Materials and Electronic Devices

BD tested in the same conditions (η= 7.5 vs 6.1%; TiO2: 10 + 4µm, dye: 0.5 mM t-butanol / acetonitrile 1:1 with with CDCA 0.5 mM, electrolyte: 0.6 M [bmim][I], 0.03MI2, 0.1MGuSCNand0.5Mt-bupyinCH3CN/valeronitrile85:15). Figure 17. Ancillary ligands modifications of complex 6 [101]. In the same paper, a Ru complex was reported, in which the bipyridine bears two carboxyl substituents. While having four anchoring groups, this complex led to lower efficiencies (23, Figure 18). With similar purposes, Kanniyambatti [76] modified complex 5, achieving a three-anchored sensitizer (24, Figure 18) with higher molar extinction coefficient and higher efficiency with respect to both complex 5 and BD tested in the same conditions ( = 7.5 vs 6.1%; TiO2: 10 + 4 μm, dye: 0.5 mM t-butanol / acetonitrile 1:1 with with CDCA 0.5 mM, electrolyte: 0.6 M [bmim][I], 0.03 M I2, 0.1 M GuSCN and 0.5 M t-bupy in CH3CN / valeronitrile 85:15). Figure 18. Four (23) and three (24) anchored complexes by Pavan Kumar [101] and Kanniyambatti [76]. All these modifications were in line with the results from Giribabu, who proposed a Ru complex with 4,4’-dicarboxybipyridine and a tpy ligand bearing the same electron donor in 4,4’,4’’- positions (t-butyl or biphenyl amino substituted styryl moieties) (25a-b, Figure 19) [102]. In this case, a further enhancement in π-conjugation led to increased molar extinction coefficients and improved performances. Similar complexes that bear donating groups on the terpyridine and electron withdrawing/grafting moieties on a bidentate ligand have been proposed by Mosurkal [103], Erten-Ela [104] and, more recently, by Mongal [105]. In the first case, the anchoring moiety was provided by 4,4’-dicarboxy-2,2’-bipyridine. Mono and dinuclear ruthenium complexes were compared on the device, where the latter one gave better performances. In the second case, the bidentate ligand was represented by a phenantroline substituted with phenyl sulfonic acid moieties in order to graft and sensitize TiO2 and ZnO. Figure18. Four (23) and three (24) anchored complexes by Pavan Kumar [101] and Kanniyambatti [76]. All these modifications were in line with the results from Giribabu, who proposed a Ru complex with 4,4’-dicarboxybipyridine and a tpy ligand bearing thesameelectrondonor in4,4’,4”-positions (t-butylorbiphenylaminosubstituted s yryl moieties) (25a-b, Figure 19) [102]. In this case, a further enhancement in pi-conjugation led to increased molar extinction coefficients and i proved performances. Similar complexes that bear donating groups on the terpyridine and electronwithdrawing/graftingmoietiesonabidentateligandhavebeenproposedby Mosurkal [103], Erten-Ela [104] and, more recently, by Mongal [105]. In the first case, the anchoring moiety was provided by 4,4’-dicarboxy-2,2’-bipyridine. Mono and dinuclearrutheniumcomplexeswerecomparedonthedevice,where the latterone gavebetterperformances. In thesecondcase, thebidentate ligandwasrepresented byaphenantrolinesubstitutedwithphenylsulfonicacidmoieties inorder tograft andsensitizeTiO2 andZnO. 31