title: Highly ordered and vertically oriented TiO2/Al2O3 nanotube electrodes for application in dye-sensitized solar cells.
abstract: The surface of long TiO2 nanotube (NT) electrodes in dye-sensitized solar cells (DSSCs) was modified without post-annealing by using atomic layer deposition (ALD) for the enhancement of photovoltage. Vertically oriented TiO2 NT electrodes with highly ordered and crack-free surface structures over large areas were prepared by a two-step anodization method. The prepared TiO2 NTs had a pore size of 80 nm, and a length of 23 μm. Onto these TiO2 NTs, an Al2O3 shell of a precisely controlled thickness was deposited by ALD. The conformally coated shell layer was confirmed by high-resolution transmission electron microscopy, energy-dispersive x-ray spectroscopy, and x-ray photoelectron spectroscopy. The open-circuit voltage (V(oc)) of the DSSCs was gradually enhanced as the thickness of the Al2O3 shell of the TiO2/Al2O3 NT electrodes was increased, which resulted from the enhanced electron lifetime. The enhanced electron lifetime caused by the energy barrier effect of the shell layer was measured quantitatively by the open-circuit voltage decay technique. As a result, 1- and 2-cycle-coated samples showed enhanced conversion efficiencies compared to the bare sample.
authors.affiliation: Korea Institute of Science and Technology, Photo-Electronic Hybrids Research Center, Seoul 136-791, Korea.
authors.forename: Jae-Yup
authors.initials: JY
authors.lastname: Kim
authors.forename: Kyeong-Hwan
authors.initials: KH
authors.lastname: Lee
authors.forename: Junyoung
authors.initials: J
authors.lastname: Shin
authors.forename: Sun Ha
authors.initials: SH
authors.lastname: Park
authors.forename: Jin Soo
authors.initials: JS
authors.lastname: Kang
authors.forename: Kyu Seok
authors.initials: KS
authors.lastname: Han
authors.forename: Myung Mo
authors.initials: MM
authors.lastname: Sung
authors.forename: Nicola
authors.initials: N
authors.lastname: Pinna
authors.forename: Yung-Eun
authors.initials: YE
authors.lastname: Sung