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Keywords:

  • electrochemistry;
  • energy conversion;
  • heterocycles;
  • osmium;
  • sensitizers

Abstract

A series of OsII sensitizers (TFOS-x, in which x=1, 2, or 3) with a single 4,4′-dicarboxy-2,2′-dipyridine (H2dcbpy) anchor and two chelating 2-pyridyl (or 2-pyrimidyl) triazolate ancillaries was successfully prepared. Single-crystal X-ray structural analysis showed that the core geometry of the OsII-based sensitizers consisted of one H2dcbpy unit and two eclipsed cis-triazolate fragments; this was notably different from the RuII-based counterparts, in which the azolate (both pyrazolate and triazolate) fragments are located at the mutual trans-positions. The basic properties were extensively probed by using spectroscopic and electrochemical methods as well as time-dependent density functional theory (TD-DFT) calculations. Fabrication of dye-sensitized solar cells (DSCs) was then attempted by using the I/I3-based electrolyte solution. One such DSC device, which utilized TFOS-2 as the sensitizer, showed promising performance characteristics with a short-circuit current density (JSC) of 15.7 mA cm−2, an open-circuit voltage of 610 mV, a fill factor of 0.63, and a power conversion efficiency of 6.08 % under AM 1.5G simulated one-sun irradiation. Importantly, adequate incident photon-to-current conversion efficiency performances were observed for all TFOS derivatives over the wide spectral region of 450 to 950 nm, showing a panchromatic light harvesting capability that extended into the near-infrared regime. Our results underlined a feasible strategy for maximizing JSC and increasing the efficiency of DSCs.