Page - 44 - in Photovoltaic Materials and Electronic Devices

Recently, Li used 2,2’-dipyrromethanes as NˆN’ bidentate ligand in order to substitute thiocyanates in the BD structure. The dipyrromethanes having 5-pentafluorophenyl and 2-thienyl substituents gave IPCE curves showing a sensitizationupto950nm(45, Figure36) [146]. Figure 35. Phosphine-coordinated Ru(II) ensitizer by Kinoshita et al. [144]. Recently, Li used 2,2’-dipyrromethanes as N^N’ bidentate ligand in order to substitute thiocyanates in the BD structure. The dipyrromethanes having 5-pentafluorophenyl and 2-thienyl substituents gave IPCE curves showing a sensitization up to 950 nm (45, Figure 36) [146]. Figure 36. 2,2’-Dipyrromethane by Li et al. [146]. A bidentate benzimidazole was tested by Swetha et al. [147] as ancillary ligand in a Ru complex with tctpy, showing blueshifted absorption and a higher molecular extinction coefficient in the high energy region of the solar spectrum with respect to N749, which accounted for a better IPCE in the 400-640 nm range and a 6.07% efficiency (46, Figure 37; dye: 0.3 mM CH3CN / n-butanol 1:1 with 20 mM DCA, electrolyte: 0.5 M DMPII, 0.05 M I2, 0.1 M LiI CH3CN / butanol 1:1). Figure36. 2,2’-DipyrromethanebyLi et al. [146]. A bidentate benzimidazole was tested by Swetha et al. [147] as ancillary ligand in a Ru complex with tctpy, showing blueshifted absorption and a higher molecular extinction coefficient in the high energy region of the solar spectrum with respect to N749, which accounted for a better IPCE in the 400–640 nm range and a 6.07% efficiency (46, Figure 37; dye: 0.3 mM CH3CN / n-butanol 1:1 with 20 mM DCA, electrolyte: 0.5MDMPII,0.05MI2, 0.1MLiICH3CN/butanol1:1). Figure 35. Phosphine-coordinated Ru(II) sensitizer by Kinoshita et al. [144]. Recently, Li used 2,2’-dipyrromethanes as N^N’ bidentate ligand in order to substitute thiocyanates in the BD structure. The dipyrromethanes having 5-pentafluorophenyl and 2-thienyl substituents gave IPCE curves showing a sensitization up to 950 nm (45, Figure 36) [146]. Figure 36. 2,2’-Dipyrromethane by Li et al. [146]. A bidentate benzimidazole was tested by Swetha et al. [147] as ancilla y ligand in a Ru complex with tctpy, showing blueshifted absorption and a higher molecular extinction coefficient in the high energy r gion of the solar sp ctrum with respect to N749, which accounted for a better IPCE in the 400-640 nm range and a 6.07% efficiency (46, Figure 37; dye: 0.3 mM CH3CN / n-butanol 1:1 with 20 mM DCA, electrolyte: 0.5 M DMPII, 0.05 M I2, 0.1 M LiI CH3CN / butanol 1:1). Figure37. Benzimidazole ligandtestedbySwetha et al. [147]. 3.3. ExchangeofMetalCenter Terpyridine complexes with other metals were reported by Bignozzi’s group, who complexed osmium with tctpy, various bipyridines and pyridylquinoline [148–150]. The idea was to further broaden absorption spectra thanks to Os(II) complexes characterized by high spin-orbit coupling constant that allows the direct population of low energy, spin-forbidden, 3MLCT states. No significant differences in IPCE values were found in the case of the various Os complexes showing values up to 50% at 900 nm and 70% in the visible region. 44