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

Yunyue Lu; Heli Song; Xin Li; Hans Ågren; Qingyun Liu; Jiwei Zhang; Xuan Zhang; Yongshu Xie

doi:10.1021/acsami.8b19077

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

ACS Appl Mater Interfaces. 2019 Feb 6;11(5):5046-5054. doi: 10.1021/acsami.8b19077. Epub 2019 Jan 28.

Authors

Yunyue Lu¹, Heli Song¹, Xin Li², Hans Ågren², Qingyun Liu³, Jiwei Zhang⁴, Xuan Zhang⁴, Yongshu Xie¹

Affiliations

¹ Key Laboratory for Advanced Materials and Institute of Fine Chemicals, School of Chemistry and Molecular Engineering , East China University of Science & Technology , Shanghai 200237 , P. R. China.
² Division of Theoretical Chemistry and Biology, School of Biotechnology , KTH Royal Institute of Technology , SE-10691 Stockholm , Sweden.
³ College of Chemical and Environmental Engineering , Shandong University of Science and Technology , Qingdao 266510 , P. R. China.
⁴ College of Chemistry, Chemical Engineering & Biotechnology , Donghua University , Shanghai 201620 , P. R. China.

PMID: 30644719
DOI: 10.1021/acsami.8b19077

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 TiO₂ 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^-/I₃^- 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.

Keywords: coadsorption; cosensitization; phenothiazine; porphyrin; wrapped structure.