title: Design of Os(II) -based sensitizers for dye-sensitized solar cells: influence of heterocyclic ancillaries.
abstract: A series of Os(II) sensitizers (TFOS-x, in which x=1, 2, or 3) with a single 4,4'-dicarboxy-2,2'-dipyridine (H2 dcbpy) 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 Os(II) -based sensitizers consisted of one H2 dcbpy unit and two eclipsed cis-triazolate fragments; this was notably different from the Ru(II) -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.
authors.affiliation: Department of Chemistry and Low Carbon Energy Research Center, National Tsing Hua University, Hsinchu 30013 Taiwan.
authors.forename: Fa-Chun
authors.initials: FC
authors.lastname: Hu
authors.forename: Sheng-Wei
authors.initials: SW
authors.lastname: Wang
authors.forename: Miquel
authors.initials: M
authors.lastname: Planells
authors.forename: Neil
authors.initials: N
authors.lastname: Robertson
authors.forename: Harihara
authors.initials: H
authors.lastname: Padhy
authors.forename: Bo-Sian
authors.initials: BS
authors.lastname: Du
authors.forename: Yun
authors.initials: Y
authors.lastname: Chi
authors.forename: Po-Fan
authors.initials: PF
authors.lastname: Yang
authors.forename: Hao-Wu
authors.initials: HW
authors.lastname: Lin
authors.forename: Gene-Hsiang
authors.initials: GH
authors.lastname: Lee
authors.forename: Pi-Tai
authors.initials: PT
authors.lastname: Chou
mesh_terms: D004396:Coloring Agents / Q000737:chemistry*; D015195:Drug Design; D011211:Electric Power Supplies; D004563:Electrochemistry; D006571:Heterocyclic Compounds / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D009992:Osmium / Q000737:chemistry*; D012428:Ruthenium / Q000737:chemistry; D012993:Solar Energy
chemical_list: D004396:Coloring Agents; D006571:Heterocyclic Compounds; D009942:Organometallic Compounds; D009992:Osmium; D012428:Ruthenium
keywords: electrochemistry; energy conversion; heterocycles; osmium; sensitizers