The absorption properties of pi-extended macrocycles such as porphyrins and phthalocyanines have been intensively applied to the light -harvesting process related to organic photovoltaics, with particular focus on polymer cells and Dye-Sensitized Solar Cells. In the last few years a large amount of new phthalocyanines have been synthesized and studied and amongst them an interesting sterically hindered push-pull structure, having a record efficiency value of 6.4% has been prepared and published. Even if porphyrins have obtained higher values in terms of efficiency, having the most efficient ones recently shown an impressive efficiency value of 12%, thus comparable to that of N719, the outstanding stability and high molar extinction coefficients (e> 10E5) of phthalocyanines make them very attractive sensitizers with possible applications in Graetzel cells and justify the intensive study carried on these molecules. It is well known that the metal centers of these macrocyclic compounds can affect their absorption peaks, their HOMO/LUMO energy values as well as their possible charge transfer properties in a DSSC device. Thus our goal was to investigate the performances of dyes possessing the same molecular structure having different central metal ions, in order to understand how their harvesting capabilities could be influenced by this kind of substitution. In particular we have chosen an unsymmetric tri-ter-butyl phthalocyanine bearing an ethynylbenzoic unit as anchoring group to the TiO2, that have been synthesized and fully characterized by our research group some years ago as zinc complex. In the present contribution, the synthesis of different 9(10),16(17),23(24)-tri-ter-butyl-2-[acetynyl-(4-carboxy)phenyl]phthalocyaninato metal complexes and their optical, chemical and electrochemical characterizations will be presented. The related free-base phthalocyanine will also be analyzed. Theoretical calculations of both frontier molecular orbitals and simulated absorption spectra with the preliminary measurements of the related DSSCs, where obtained, will be also discussed.
The effect of the central metal ion on photovoltaic performances of phthalocyanines used as sensitizers in DSSC
G Zanotti;A Amore Bonapasta;N Angelini;G Mattioli;AM Paoletti;G Pennesi;G Rossi;D Caschera;G Gigli
2014
Abstract
The absorption properties of pi-extended macrocycles such as porphyrins and phthalocyanines have been intensively applied to the light -harvesting process related to organic photovoltaics, with particular focus on polymer cells and Dye-Sensitized Solar Cells. In the last few years a large amount of new phthalocyanines have been synthesized and studied and amongst them an interesting sterically hindered push-pull structure, having a record efficiency value of 6.4% has been prepared and published. Even if porphyrins have obtained higher values in terms of efficiency, having the most efficient ones recently shown an impressive efficiency value of 12%, thus comparable to that of N719, the outstanding stability and high molar extinction coefficients (e> 10E5) of phthalocyanines make them very attractive sensitizers with possible applications in Graetzel cells and justify the intensive study carried on these molecules. It is well known that the metal centers of these macrocyclic compounds can affect their absorption peaks, their HOMO/LUMO energy values as well as their possible charge transfer properties in a DSSC device. Thus our goal was to investigate the performances of dyes possessing the same molecular structure having different central metal ions, in order to understand how their harvesting capabilities could be influenced by this kind of substitution. In particular we have chosen an unsymmetric tri-ter-butyl phthalocyanine bearing an ethynylbenzoic unit as anchoring group to the TiO2, that have been synthesized and fully characterized by our research group some years ago as zinc complex. In the present contribution, the synthesis of different 9(10),16(17),23(24)-tri-ter-butyl-2-[acetynyl-(4-carboxy)phenyl]phthalocyaninato metal complexes and their optical, chemical and electrochemical characterizations will be presented. The related free-base phthalocyanine will also be analyzed. Theoretical calculations of both frontier molecular orbitals and simulated absorption spectra with the preliminary measurements of the related DSSCs, where obtained, will be also discussed.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
