Seite - 37 - in Photovoltaic Materials and Electronic Devices

performanceswithrespect toBD[129]. Morerecently, the terminalpyridylunitof the tctpy was replaced with variously substituted quinolines (34, Figure 26) reaching goodperformances (η=10.19%;TiO2: 15+7µm,dye: 0.3mMethanol/ t-butanol 1:1 with 0.6 mM of tetra-butylammonium deoxycholate, electrolyte: 0.6 M DMPII, 0.05MLiI,0.05MI2, 0.5Mt-bupyinCH3CN)[130]. In thisnewfamilyofcomplexes, electron-donating-bulky t-butyl substituentson quinoline gave better performances with respect to the electron-withdrawing COOH group. With the t-butyl group, in fact, a blueshift for transitions at lower energies was reported together with a hyperchromic effect that improved IPCE and Jsc. Further modifications to the bidentateancillaryligandsledtoabestresultefficiency(η=11.16%;withtheaddition of1mMDCAasco-adsorbate to thedyesolutionandelectrolyte: 0.1MLiIand0.1M GuNCS, 0.5 M t-bupy in CH3CN) [22] when tctpy and hexylthiothienyl-substituted pyrazolyl-pyridinewereusedtocomplexruthenium(II) (35,Figure25). Thiscomplex showedworseconversionintheNIRspectralregionbutimprovedIPCEinthevisible onewithrespect toBD, thusdeterminingabetterefficiency in thesameconditions.Materials 2016, 9, 137 19 of 37 Figure 26. Pyridyl-pyrazolate ligand and quinolyl-bipyridine ligand for Ru(II)-complexes [22,127-129]. 3.2.6. Phenyl Bipyridines In 2007 Wadman et al. [132] compared a bis-tpy Ru complex bearing one carboxyl group in the 4- position, with two structurally homolog complexes in which the tpy was replaced by 6-phenylbipyridines, with one or two carboxyl groups (36 and 37, Figure 27). The N^N’^C Ru(II)-complex with two anchoring groups showed performances similar to N719. Thus, in 2010 [133], the same group further extendend the series, including N^C^N’ ligands based on 3,5-bis(2-pyridyl)benzoic acid (38, Figure 27). Figure 26. Pyridyl-pyrazolate ligand and quinolyl-bipyridine ligand for Ru(II)-complexes [22,127–129]. 37