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Polymer‐Based Ruthenium(II) Polypyridyl Chromophores on TiO 2 for Solar Energy Conversion
Author(s) -
Leem Gyu,
Morseth Zachary A.,
Wee KyungRyang,
Jiang Junlin,
Brennaman M. Kyle,
Papanikolas John M.,
Schanze Kirk S.
Publication year - 2016
Publication title -
chemistry – an asian journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.18
H-Index - 106
eISSN - 1861-471X
pISSN - 1861-4728
DOI - 10.1002/asia.201501384
Subject(s) - ruthenium , photocurrent , photochemistry , dye sensitized solar cell , materials science , chromophore , chemistry , optoelectronics , electrolyte , electrode , organic chemistry , catalysis
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 TiO 2 films (TiO 2 //PS‐Ru‐A). Studies of the resulting TiO 2 //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 TiO 2 film. Monochromatic light photocurrent spectroscopy (IPCE) and white light (AM1.5G) current–voltage studies of dye‐sensitized solar cells using the TiO 2 //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 TiO 2 //PS‐Ru‐A films was tested and compared to a monomeric Ru II complex (TiO 2 //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 TiO 2 //Ru‐A, while time‐resolved emission measurements reveal delayed electron injection occurring in TiO 2 //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.