title: Polymer-Based Ruthenium(II) Polypyridyl Chromophores on TiO2 for Solar Energy Conversion.
abstract: A polychromophoric light-harvesting assembly featuring a polystyrene (PS) backbone with ionic carboxylate-functionalized Ru(II) polypyridyl complexes as pendant groups (PS-Ru-A) was synthesized and successfully anchored onto mesoporous structured TiO2 films (TiO2 //PS-Ru-A). Studies of the resulting TiO2 //PS-Ru-A films carried out by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and atomic force microscopy (AFM) confirmed that the ionic carboxylated Ru(II) complexes from PS-Ru-A led to the surface immobilization on the TiO2 film. Monochromatic light photocurrent spectroscopy (IPCE) and white light (AM1.5G) current-voltage studies of dye-sensitized solar cells using the TiO2 //PS-Ru-A photoanode give rise to modest photocurrent and white light efficiency (24 % peak IPCE and 0.33 % PCE, respectively). The photostability of surface-bound TiO2 //PS-Ru-A films was tested and compared to a monomeric Ru(II) complex (TiO2 //Ru-A), showing an enhancement of ∼14 % in the photostability of PS-Ru-A. Transient absorption measurements reveal that electron injection from surface-bound pendants occurs on the picosecond time scale, similar to TiO2 //Ru-A, while time-resolved emission measurements reveal delayed electron injection occurring in TiO2 //PS-Ru-A on the nanosecond time scale, underscoring energy transport from unbound to surface-bound complexes. Additionally, charge recombination is delayed in PS-Ru-A, pointing towards intra-assembly hole transport to complexes away from the surface. Molecular dynamics simulations of PS-Ru-A in fluid solution indicate that a majority of the pendant Ru(II) complexes lie within 10-20 Å of each other, facilitating efficient energy- and charge transport among the pendant complexes.
authors: Department of Chemistry, University of Florida, Gainesville, Florida, 32611, United States.
authors: Gyu
authors: G
authors: Leem
authors: Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, 27599, United States.
authors: Zachary A
authors: ZA
authors: Morseth
authors: Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, 27599, United States.
authors: Kyung-Ryang
authors: KR
authors: Wee
authors: Department of Chemistry, University of Florida, Gainesville, Florida, 32611, United States.
authors: Junlin
authors: J
authors: Jiang
authors: Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, 27599, United States.
authors: M Kyle
authors: MK
authors: Brennaman
authors: Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, 27599, United States.
authors: John M
authors: JM
authors: Papanikolas
authors: Department of Chemistry, University of Florida, Gainesville, Florida, 32611, United States. kschanze@chem.ufl.edu.
authors: Kirk S
authors: KS
authors: Schanze
keywords: chromophores; dye-sensitized solar cells; energy transfer; molecular dynamics; ruthenium