Fluorene-based sensitizers with a phenothiazine donor: Effect of mode of donor tethering on the performance of dye-sensitized solar cells

Abhishek Baheti, K. R. Justin Thomas*, Chun Ting Li, Chuan Pei Lee, Kuo Chuan Ho

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

84 Citations (Scopus)


Two types of fluorene-based organic dyes featuring T-shape/rod-shape molecular configuration with phenothiazine donor and cyanoacrylic acid acceptor have been synthesized and characterized as sensitizers for dye-sensitized solar cells. Phenothiazine is functionalized at either nitrogen (N10) or carbon (C3) to obtain T-shape and rod-like organic dyes, respectively. The effect of structural alternation on the optical, electrochemical, and the photovoltaic properties is investigated. The crystal structure determination of the dye containing phenyl linker revealed cofacial slip-stack columnar packing of the molecules. The trends in the optical properties of the dyes are interpreted using time-dependent density functional theory (TDDFT) computations. The rod-shaped dyes exhibited longer wavelength absorption and low oxidation potentials when compared to the corresponding T-shaped dyes attributable to the favorable electronic overlap between the phenothiazine unit and the rest of the molecule in the former dyes. However, the T-shaped dyes showed better photovoltaic properties due to the lowest unoccupied molecular orbital (LUMO) energy level favorable for electron injection into the conduction band of TiO2 and appropriate orientation of the phenothiazine unit rendering effective surface blocking to suppress the recombination of electrons between the electrolyte I3- and TiO2. The electrochemical impedance spectroscopy investigations provide further support for the variations in the electron injection and transfer kinetics due to the structural modifications.

Original languageEnglish
Pages (from-to)2249-2262
Number of pages14
JournalACS Applied Materials and Interfaces
Issue number4
Publication statusPublished - 2015 Feb 4
Externally publishedYes


  • TDDFT computations
  • dye-sensitized solar cells
  • electrochemical impedance spectroscopy
  • optical spectra
  • organic dyes
  • phenothiazine

ASJC Scopus subject areas

  • General Materials Science


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