Synthesis and characterization of porphyrin sensitizers with various electron-donating substituents for highly efficient dye-sensitized solar cells

Abstract

A series of porphyrin dyes with an electron-donating group (EDG) attached at a meso-position (YD1-YD8) have been designed and synthesized for use as sensitizers in dye-sensitized solar cells (DSSC). The nature of the EDG exerts a significant influence on the spectral, electrochemical and photovoltaic properties of these sensitizers. Absorption spectra of porphyrins having an amino group show broadened Soret band and red-shifted Q bands with respect to those of reference porphyrin YD0. This phenomenon is more pronounced for porphyrins YD7 and YD8 that have a pi-conjugated triphenylamine at the meso-position opposite the anchoring group. Upon introduction of an EDG at the meso-position, the potential for the first oxidation alters significantly to the negative whereas that for the first reduction changes inappreciably, indicating a decreased HOMO-LUMO gap. Results of density-functional theory (DFT) calculations support the spectroelectrochemical data for a delocalization of charge between the porphyrin ring and the amino group in the first oxidative state of diarylamino-substituted porphyrins YD1-YD4, which exhibit superior photovoltaic performance among all porphyrins under investigation. With long-chain alkyl groups on the diarylamino substituent, YD2 shows the best cell performance with J(SC) = 13.4 mA cm(-2), V(OC) = 0.71 V, and FF = 0.69, giving an overall efficiency 6.6% of power conversion under simulated one-sun AM1.5 illumination

Porphyrin Based Dye Sensitized Solar Cells

“…Hsieh et al extended such investigations when they tested a comprehensive range of electron donors and acceptors attached to the same porphyrin core. They demonstrated that several different electron donors attached to the optimal position of the porphyrin core were able to increase both the J sc and the V oc of the DSSCs, attributing this result to improved electron injection and reduced recombination due to the localization of electron density in the dye upon photoexcitation (Hsieh, Lu et al, 2010). From equation (6) it is clear that the electronic coupling, and thus the rate of electron transfer for injection, is strongly dependent on the distance over which electron transfer occurs.…”

Effect of the anchoring group in porphyrin sensitizers: phosphonate versus carboxylate linkages

“…Other molecular structures of push-pull zinc porphyrins were synthesized and studied in DSSCs by the groups of Yeh and Diau. 29,30 Some of the studied systems exhibited excellent cell performances and outperformed 20-based DSSCs. However, for all these sensitizers, conversion efficiencies remained below 8%.…”

“…Odobel and coworkers have prepared a series of porphyrins sensitizers (28)(29)(30)(31)(32) where the phosphonic group was the anchoring entity (Scheme 8).…”

Test of Different Sensitizing Dyes in Dye-Sensitized Solar Cells Based on Nb2O5 Photoanodes

“…In the latter, the photoanodes were autoclaved at 90 °C for 12 h in 100 mL of sensitizing dye solution. The dye solutions' compositions were chosen according to the best ones reported in the literature for TiO2 [17][18][19][20][21][22]:  N749: mixture of acetonitrile and tert-butyl alcohol (volume ratio: 1/1), 500 µM dye concentration and 20 mM chenodeoxycholic acid concentration; Figure 10. IPCE curves used to calculate the dye-coverage variation (%): (a) IPCE curves of DNF15, N749 and DNF11 devices; (b) IPCE curves of DNF01 and DNF12 devices.…”

“…To the best of our knowledge, none of the previous researches in the literature presents the optimization of the sensitizers for DSSCs relying on Nb 2 O 5 photoanodes. The dyes were chosen among both metal-complex dyes (two Ru-based dyes, N749 and C106, and one Zn-based dye, DNF12) [17][18][19] and metal-free organic dyes (DNF01, DNF11 and DNF15) [20][21][22]. Sensitizers were chosen in such a way to cover a broad range of light absorption (from 440 nm to 960 nm), obviously taking into account the necessity of the redox potential of the electrolyte active species (I − /I 3 − ) and the conduction band edge of the semiconductor to be, energetically, into the dye's absorption gap.…”