title: High-Performance and Stable Gel-State Dye-Sensitized Solar Cells Using Anodic TiO2 Nanotube Arrays and Polymer-Based Gel Electrolytes.
abstract: Highly ordered and vertically oriented TiO2 nanotube (NT) arrays were synthesized with potentiostatic anodization of Ti foil and applied to fabricate gel-state dye-sensitized solar cells (DSSCs). The open structure of the TiO2 NT facilitates the infiltration of the gel-state electrolyte; their one-dimensional structural feature provides effective charge transport. TiO2 NTs of length L=15-35 μm were produced on anodization for periods of t=5-15 h at a constant voltage of 60 V, and sensitized with N719 for photovoltaic characterization. A commercially available copolymer, poly(methyl methacrylate-co-ethyl acrylate) (PMMA-EA), served as a gelling agent to prepare a polymer-gel electrolyte (PGE) for DSSC applications. The PGE as prepared exhibited a maximum conductivity of 4.58 mS cm(-1) with PMMA-EA (7 wt %). The phase transition temperature (Tp) of the PGE containing PMMA-EA at varied concentrations was determined on the basis of the viscosities measured at varied temperatures. Tp increased with increasing concentration of PMMA-EA. An NT-DSSC with L=30 μm assembled using a PGE containing PMMA-EA (7 wt %) exhibited an overall power conversion efficiency (PCE) of 6.9%, which is comparable with that of a corresponding liquid-type device, PCE=7.1%. Moreover, the gel-state NT-DSSC exhibited excellent thermal and light-soaking enduring stability: the best device retained ∼90% of its initial efficiency after 1000 h under 1 sun of illumination at 50 °C, whereas its liquid-state counterpart decayed appreciably after light soaking for 500 h.
authors.affiliation: †Atomic and Molecular Group, Physics Department, Tarbiat Modares University, P.O. Box 14115-175, Tehran, Iran.
authors.forename: Zahra
authors.initials: Z
authors.lastname: Seidalilir
authors.affiliation: †Atomic and Molecular Group, Physics Department, Tarbiat Modares University, P.O. Box 14115-175, Tehran, Iran.
authors.forename: Rasoul
authors.initials: R
authors.lastname: Malekfar
authors.affiliation: ‡Department of Applied Chemistry and Institute of Molecular Science, National Chiao Tung University, Hsinchu 30010, Taiwan.
authors.forename: Hui-Ping
authors.initials: HP
authors.lastname: Wu
authors.affiliation: ‡Department of Applied Chemistry and Institute of Molecular Science, National Chiao Tung University, Hsinchu 30010, Taiwan.
authors.forename: Jia-Wei
authors.initials: JW
authors.lastname: Shiu
authors.affiliation: ‡Department of Applied Chemistry and Institute of Molecular Science, National Chiao Tung University, Hsinchu 30010, Taiwan.
authors.forename: Eric Wei-Guang
authors.initials: EW
authors.lastname: Diau
keywords: DSSC; PMMA-EA; TiO2 nanotubes; anodization; polymer-gel electrolyte