Tuning the Photovoltaic Performance of DSSCs by Appending Various Donor Groups on trans-Dimesityl Porphyrin Backbone

Abstract

Five cost-effective porphyrin based sensitizers with various donor groups (bisthiophene, N,N-dimethylaminophenyl, triphenylamine, carbazole and phenothiazine) and meso-dimesityl as auxiliary groups have been synthesized through the shortest possible synthetic route for the practical commercialization of these dyes. trans-A2BC porphyrin dyes show power conversion efficiencies (η) ranging from 5.3% to 7.11% under 1 sun illumination and highly depend on donor strength of appended moiety. Our molecular design incorporates trans-10,20-dimesityl groups, which prevents the π–π aggregation between the porphyrin units onto the TiO2 surface. The porphyrin dye (RA-200-Zn) bearing phenothiazine as donor unveils the highest photon-to-current conversion efficiency (PCE) of 7.1% and showed butterfly conformation, which can restrict the intermolecular aggregation. Further, this dye shows a broader absorption on TiO2 surface and significantly increased IPCE values in visible region as compared to the other dyes, which assured better light harvesting ability with high short-circuit current density (J sc) of 14.2 mA cm–2.

Synthesis, Spectral, Electrochemical and Photovoltaic Studies of A3B Porphyrinic Dyes having Peripheral Donors

“…[20] This broader, red-shifted absorption spectra, and the observed enhancement in the molar extinction coefficient of the Q-bands may be arisen from the presence of extended π-conjugation and asymmetry introduced via substitution. Interestingly, the Soret band of these dyes also showed significant broadening compared to its mono-substituted analogue.…”

“…[14,15] Additionally, higher conversion efficiency could be achieved by harnessing the sunlight at longer wavelengths or near-IR region. [18][19][20][21] Many donor substituents such as phenothiazine, diarylamino, anthracene, carbazole, fluorene, have been appended on porphyrin structures for improving their DSSC efficiency. [18][19][20][21] Many donor substituents such as phenothiazine, diarylamino, anthracene, carbazole, fluorene, have been appended on porphyrin structures for improving their DSSC efficiency.…”

“…[22][23][24][25][26] N,N-Diarylamino, carbazole and phenothiazine have been prominently utilized as excellent donor groups in porphyrin dyes. [20][21][22]25,29,30] Xie and coworkers developed many porphyrin sensitizers by the introduction of modified phenothiazine group with its N-phenyl group wrapped with alkoxy chains; such porphyrin sensitizers showed enhanced PCE values ranging from 9.7 to 11.7 %. [20][21][22]25,29,30] Xie and coworkers developed many porphyrin sensitizers by the introduction of modified phenothiazine group with its N-phenyl group wrapped with alkoxy chains; such porphyrin sensitizers showed enhanced PCE values ranging from 9.7 to 11.7 %.…”

“…[22] Indoline substituted porphyrin dyes are reported to yield PCE conversion efficiency upto 10 %. [20,32,33] Recently, a new set of push-pull zinc porphyrin sensitizers revealed an impressive PCE of 13-14 %. This brings out the significance of structural modification of the dyes to alleviate dye aggregation.…”

“…[37,38] Chenodeoxycholic acid is a widely used co-absorbent for porphyrin dyes which effectively reduces the dye aggregation of porphyrin molecules on TiO 2 surface and increases charge injection efficiency. [20,25] Although trans-A 2 B 2 porphyrins have higher number of donor groups relative to trans-A 2 BC, the highest efficiency of about 5.5 % was obtained for trans-A 2 B 2 than trans-A 2 BC (η =~7.1 %), mainly due to absence of bulky groups to reduce the dye aggregation process. [40] Imahori and coworkers have shown that the dyes having multiple N,N-diarylamino groups improve the power conversion efficiency.…”