Multiply Wrapped Porphyrin Dyes with a Phenothiazine Donor: A High Efficiency of 11.7% Achieved through a Synergetic Coadsorption and Cosensitization Approach

Abstract

Photocurrent (J sc ) and photovoltage (V oc ) are two important parameters for dye-sensitized solar cells (DSSCs) to achieve high power conversion efficiencies (PCEs). Herein, we synthesize four novel porphyrin dyes, XW36−XW39, using an N-phenyl-substituted phenothiazine donor to pursue higher PCE. For XW36 and XW37, the N-phenyl group is wrapped with two ortho-alkoxy chains. In contrast, it is substituted with a para-alkoxy group in XW38 and XW39. The phenothiazine wrapping in XW36 and XW37 induces more serious distortion, which is beneficial for anti-aggregation but unfavorable for the electron transfer from donor to a porphyrin framework. Thus, individual porphyrin dyes XW36 and XW37 exhibit efficiencies of 9.05 and 9.58%, respectively, lower than those of 9.51 and 10.0% achieved for XW38 and XW39, respectively. Besides, the introduction of a methyl group into a benzoic acid acceptor unit is conducive to anti-aggregation and thus improves the V oc and efficiencies. Therefore, higher efficiencies were achieved for XW37 and XW39, compared with XW36 and XW38, respectively. Interestingly, although the individual XW36 dye shows a lowest efficiency among the four dyes, a highest efficiency of 11.7% was obtained for XW36 on the basis of synergetic adsorption with chenodeoxycholic acid and PT-C6 because of simultaneously improved J sc and V oc , which may be ascribed to the lowest dye-loading amount of XW36 among all of these porphyrin dyes, with the largest vacancy area left on the TiO 2 surface available for cosensitizer PT-C6, resulting in a highest J sc . The high efficiency of 11.7% is one of the highest efficiencies using I − /I 3 − electrolytes in DSSCs. These results provide an effective strategy for developing efficient DSSCs by the targeted coadsorption and cosensitization of porphyrin sensitizers optimized through introducing a bis(ortho-alkoxy)-wrapped phenyl group into the phenothiazine donor and/or methyl groups into the benzoic acid acceptor unit.

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

“…The detailed preparation method of the working and counter electrodes is described in SI. [29,38] Notably, only a fewer porphyrin dyes are reported where DSSCs showed higher J sc value (> 18.5 mA/cm À 2 ). RA-195-Zn and RA-200-Zn exhibited comparable PCE values which was lower than our previous studies.…”

“…[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. [27][28][29][30] The introduction of phenothiazine moiety is also favoravable for porphyrin dyes as its N-phenyl group can play an important role in reducing aggergation of porphyrins. [27][28][29][30] The introduction of phenothiazine moiety is also favoravable for porphyrin dyes as its N-phenyl group can play an important role in reducing aggergation of porphyrins.…”

“…[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 %.…”

Solar Cells Sensitized with Porphyrin Dyes Containing Oligo(Ethylene Glycol) Units: A High Efficiency Beyond 12 %

“… Molecular structures of XW39 , XW42–XW44 , and PT‐C6 , and the synthetic route for XW42–XW44 . Reaction conditions: (i) Pd(PPh 3 ) 4 , CuI, methyl 4‐ethynyl‐3‐methylbenzoate, tetrabutylammonium fluoride, THF, Et 3 N; (ii) D n ‐Br ( n =1, 2, 3), Pd 2 (dba) 3 , AsPh 3 , THF, Et 3 N; (iii) LiOH⋅H 2 O, THF, H 2 O.…”

“…Considering the effectiveness of synergetic coadsorption and cosensitization for the enhancement of the efficiencies, chenodeoxycholic acid (CDCA) and PT‐C6 (a metal‐free organic dye) [50] (Figure S1 in the Supporting Information) were used as the coadsorbent and cosensitizer, respectively, to suppress dye aggregation and fill up the absorption valleys of the porphyrin dyes . As a consequence, a highest efficiency of 12.10 % was obtained for the XW43 +CDCA+ PT‐C6 system, which ranks among the highest efficiencies of solar cells based on the traditional iodine electrolyte …”