Up to now, the best performance in a dye-sensitized solar cell (DSSC) has been reached by a well-engineered meso disubstituted push-pull ZnII-porphyrinate.1 Porphyrins, in fact, are a very promising class of dyes because of their high chemical and photochemical stability and their very strong absorption bands. In addition, they have many reaction sites, both in meso and ?-pyrrolic position which make their spectroscopic, electrochemical and therefore light harvesting properties tunable by specific chemical functionalization: thus, now the literature defines porphyrin-sensitized solar cells as PSSCs.2 Recently, we have pointed out that ? mono or disubstituted push-pull metal porphyrinic dyes, characterised by a higher HOMO-LUMO energy gap than their meso counterparts, show nevertheless comparable or better efficiencies when acting as sensitizers in PSSCs.3 In particular, the ? mono substitution produces incident photon-to-current conversion efficiency (IPCE) spectra with a relevant intensity over a broad range of wavelengths (350-650 nm), while in the case of push-pull meso disubstitution IPCE spectra are characterised by two well-separated peaks, corresponding to the Soret and the Q absorption bands.2 In order to obtain extended and intense IPCE spectra also in the case of push-pull meso disusbtituted dyes, a possible strategy may be the introduction of a dithienylethylene (DTE) system to bridge the ZnII-porphyrinic ring and the anchoring carboxylic group of the dye.4 This extended ? system produces a relevant absorption between 450 and 650 nm and, consequently, intense IPCE values in this region.4 In the present contribution, by an electrochemical and theoretical investigation together with the comparative evaluation of their performances as dyes in PSSCs, we will discuss this latter effect on a series of ? substituted ZnII-porphyrinates with a DTE system carrying a cyanoacrylic anchoring group and linked to the ? position through an ethynyl or ethenyl or 4-ethynylstyryl bridge.
ZnII-porphyrinates with a dithienylethylene moiety linked in ?-pyrrolic position by different ? bridges: a panchromatic-dye approach to PSSCs
A Orbelli Biroli;
2013
Abstract
Up to now, the best performance in a dye-sensitized solar cell (DSSC) has been reached by a well-engineered meso disubstituted push-pull ZnII-porphyrinate.1 Porphyrins, in fact, are a very promising class of dyes because of their high chemical and photochemical stability and their very strong absorption bands. In addition, they have many reaction sites, both in meso and ?-pyrrolic position which make their spectroscopic, electrochemical and therefore light harvesting properties tunable by specific chemical functionalization: thus, now the literature defines porphyrin-sensitized solar cells as PSSCs.2 Recently, we have pointed out that ? mono or disubstituted push-pull metal porphyrinic dyes, characterised by a higher HOMO-LUMO energy gap than their meso counterparts, show nevertheless comparable or better efficiencies when acting as sensitizers in PSSCs.3 In particular, the ? mono substitution produces incident photon-to-current conversion efficiency (IPCE) spectra with a relevant intensity over a broad range of wavelengths (350-650 nm), while in the case of push-pull meso disubstitution IPCE spectra are characterised by two well-separated peaks, corresponding to the Soret and the Q absorption bands.2 In order to obtain extended and intense IPCE spectra also in the case of push-pull meso disusbtituted dyes, a possible strategy may be the introduction of a dithienylethylene (DTE) system to bridge the ZnII-porphyrinic ring and the anchoring carboxylic group of the dye.4 This extended ? system produces a relevant absorption between 450 and 650 nm and, consequently, intense IPCE values in this region.4 In the present contribution, by an electrochemical and theoretical investigation together with the comparative evaluation of their performances as dyes in PSSCs, we will discuss this latter effect on a series of ? substituted ZnII-porphyrinates with a DTE system carrying a cyanoacrylic anchoring group and linked to the ? position through an ethynyl or ethenyl or 4-ethynylstyryl bridge.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
