Comparing fluoro- and trifluoromethyl-functionalized Ni(II) 1,1-dithiolates with 1,1′-bis-(diphenylphosphino)ferrocene co-ligand in DSSC applications

Aparna Kushwaha, Devyani Srivastava, Gabriele Kociok-Köhn, Suresh W. Gosavi, Mutthupandian Ashokkumar, Ratna Chauhan, Sarfaraz Ahmed, Abhinav Kumar

Research output: Contribution to journalArticlepeer-review

Abstract

Four new heteroleptic Ni(II)-dithiolates with general formula [Ni(dppf)(dithiolate)] (dithiolate = 2-cyano-2-(4-fluorophenyl)ethene-1,1-bis(dithiolate) (Ni-1); 2-cyano-2(2-(trifluoromethyl)phenyl)ethene-1,1-bis(thiolate) (Ni-2); 2-cyano-2(3-(trifluoromethyl)phenyl)ethene-1,1-bis(thiolate) (Ni-3) and 2-cyano-2(4-(trifluoromethyl)phenyl)ethene-1,1-bis(thiolate) (Ni-4); dppf = 1,1′-bis(diphenylphosphino) ferrocene) have been synthesized and characterized spectroscopically as well as by single crystal X-ray diffraction technique. Single crystal X-ray analyses for Ni-1 and Ni-2 reveal distorted square planar geometry around Ni(II) that are satisfied by two sulfur and two phosphorus centers of the dithiolate and dppf ligands, respectively. These complexes have been used as photosensitizers in TiO2-based dye-sensitized solar cells (DSSCs) which suggest that the performance of fluoro-substituted sensitizer Ni-1 is superior to that of the other three trifluoromethyl-substituted sensitizers. Ni-1 showcases an efficiency (η) of 5.47 %, open circuit potential (Voc) of 0.699 V, short circuit current (Jsc) of 12.17 mA∙cm−2 and display 64 % incident photon-to-current conversion efficiency. The plausible reason for the variation in photovoltaic performances have been explained by integrated experimental methods and theoretical calculations. Results indicate that the small sized fluoro-group exhibits significant p-orbital overlap with the aromatic fragment of the dithiolate ligand, allowing facile photo-induced electron transfer from sensitizer to titania, thereby enhancing the electron donation from dppf→Ni(II)→dithiolate. Further, the cell fabricated with Ni-1 retains approximately 93 % of its initial conversion efficiency in 800 h time span.

Original languageEnglish
Article number176479
JournalJournal of Alloys and Compounds
Volume1008
Early online date13 Sept 2024
DOIs
Publication statusE-pub ahead of print - 13 Sept 2024

Data Availability Statement

Data will be made available on request.

Keywords

  • DOS
  • DSSC
  • Ferrocene
  • Impedance
  • Sensitizers

ASJC Scopus subject areas

  • Mechanics of Materials
  • Mechanical Engineering
  • Metals and Alloys
  • Materials Chemistry

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