Importance of binding states between photosensitizing molecules and the TiO2 surface for efficiency in a dye-sensitized solar cell

Vibrational Spectroscopy of Complex Synthetic and Industrial Products

“…This was concluded from a shift in the FTIR spectrum for the ν(C=O) mode which was higher for the N719-adsorbed TiO 2 than for that of the pure compound. Finnie et al (1998) contradicted previous reports (Murakoshi et al, 1995;Falaras, 1998) on the ester-like type of bonding and reported that the N3 molecule (same as N719 but has all acid groups and no carboxylates) complexes to TiO 2 in a bidentate chelating or bridging type of mode. In this case, Finnie et al (1998) used the splitting of carboxylate stretching bands (∆ν= ν asym (COO -) -ν sym (COO -)) to distinguish possible modes of coordination of carboxylate ion to the TiO 2 .…”

“…As a result of our large demands for energy consumption as our world population increases, the need for alternative energy sources are currently intensively investigated, in particular Dye-sensitized solar cells (DSSCs) have been given major attention due to their application in solar energy conversion and photovoltaic systems (Gratzel, 2001;Kroon et al,2007;Murakoshi et al, 1995;Falaras, 1998;Finnie et al, 1998;Nazeeruddin et al, 2003;Leon et al, 2006;Kay & Gratzel, 2002;Shklover et al, 1998;Hagfelt, 2010). In particular, the anatase TiO 2 semiconductor/Ru complex [cis -(2,2'-bipyridyl -4,4'-dicarboxylate) 2 (NCS) 2 ruthenium(II): N719] interface has been studied to understand the sensitization event via the use of spectroscopic [vibrational (Murakoshi et al, 1995;Falaras, 1998;Finnie et al, 1998;Nazeeruddin et al, 2003;Leon et al, 2006;Hagfelt, 2010) and X-ray absorption (Kay & Gratzel, 2002;Shklover et al, 1998)] and computational studies (De Angelis et al, 2007a, 2007b.…”

“…In particular, the anatase TiO 2 semiconductor/Ru complex [cis -(2,2'-bipyridyl -4,4'-dicarboxylate) 2 (NCS) 2 ruthenium(II): N719] interface has been studied to understand the sensitization event via the use of spectroscopic [vibrational (Murakoshi et al, 1995;Falaras, 1998;Finnie et al, 1998;Nazeeruddin et al, 2003;Leon et al, 2006;Hagfelt, 2010) and X-ray absorption (Kay & Gratzel, 2002;Shklover et al, 1998)] and computational studies (De Angelis et al, 2007a, 2007b. In spite of this research efforts, the binding mechanism ( Figure 11) has been debated for decades and remains of importance as it relates to electron transfer and ultimately to the performance of the dye-sensitized photoanode.…”

“…In spite of this research efforts, the binding mechanism ( Figure 11) has been debated for decades and remains of importance as it relates to electron transfer and ultimately to the performance of the dye-sensitized photoanode. For example, strong bonding interactions such as covalent bonding (owing to the strong electronic coupling between the semiconductor d-states of TiO 2 and the N719 dye molecular orbital) lead to fast electron injection processes and impact the electronic performance of the DSSC (Murakoshi et al, 1995;Wang and Lin, 2010;Bazzan et al, 2011 Murakoshi et al (1995) and Falaras (1998) were the first researchers to report that the N719 photosensitzer bonded to the TiO 2 surface via ester-like bond. This was concluded from a shift in the FTIR spectrum for the ν(C=O) mode which was higher for the N719-adsorbed TiO 2 than for that of the pure compound.…”

Solid-state carbon-13 NMR and computational characterization of the N719 ruthenium sensitizer adsorbed on TiO2 nanoparticles

“…14 We report here the characterization by MAS-NMR of carbon-13 resonances of the common DSC sensitizing dye N719 adsorbed on TiO 2 . Attempts have been made to characterize the TiO 2 -N719 interface using vibrational, [15][16][17][18][19] X-ray absorption (XAFS and XANES) 20 and photoelectron spectroscopy 21 techniques. These investigations indicate that the dye binds to the TiO 2 surface through carboxylate groups, but their number is still a matter of debate.…”