title: Densely packed siloxane barrier for blocking electron recombination in dye-sensitized solar cells.
abstract: A challenge in developing photovoltaic devices is to minimize the loss of electrons, which can seriously deteriorate energy conversion efficiency. In particular, minimizing this negative process in dye-sensitized solar cells (DSCs) is imperative. Herein, we use three different kinds of siloxanes, which are adsorbable to titania surfaces and polymerizable in forming a surface passivation layer, to reduce the electron loss. The siloxanes used are tetraethyl orthosilicate (TEOS or compound A), 1-(3-(1H-imidazol-1-yl)propyl)-3-(3-triethoxysilyl) propyl) urea (compound B), and N-(3-triethoxysilylpropyl)-N'[3-(3-methyl-1H-imidazol-3-ium) propyl] urea iodide (compound C). Titania surface passivation by either compound B or C was comparatively more effective in increasing the electron lifetime than TEOS. In the case of small-sized TEOS combined with either large-sized compound B or C, a thinner and denser passivation layer was presumably developed, thus increasing electron lifetime further. Intriguingly, device AB shows the longest electron lifetime, whereas device AC has the highest energy conversion efficiency among these experimental conditions. These results suggest that, in this special case, the electron lifetime may not be a dominant parameter in determining the energy conversion efficiency.
authors.affiliation: Center for Next Generation Dye-Sensitized Solar Cells and Department of Energy Engineering, and ‡Department of Chemical Engineering, Hanyang University , Seoul 133-791, Korea.
authors.forename: Donghoon
authors.initials: D
authors.lastname: Song
authors.forename: Hyosung
authors.initials: H
authors.lastname: An
authors.forename: Jung Hyun
authors.initials: JH
authors.lastname: Lee
authors.forename: Jung
authors.initials: J
authors.lastname: Lee
authors.forename: Hyungwoo
authors.initials: H
authors.lastname: Choi
authors.forename: In Sung
authors.initials: IS
authors.lastname: Park
authors.forename: Jong-Man
authors.initials: JM
authors.lastname: Kim
authors.forename: Yong Soo
authors.initials: YS
authors.lastname: Kang