title: Titania nanobundle networks as dye-sensitized solar cell photoanodes.
abstract: Quasi-one-dimensional (1D) titania nanobundles were synthesized via a hydrothermal method and used to print random network nanostructured films. These films are shown to be ideally suited for application as photoanodes in dye-sensitized solar cells (DSCs) as they have a higher porosity compared to the traditional 1D nanostructured TiO2 materials. Devices constructed using the N719 dye and iodide/triiodide as the redox mediator in the electrolyte yielded energy conversion efficiencies (η = 6.1 ± 0.2%), which were marginally lower than for devices made with the commonly used P25 titania films (η = 6.3 ± 0.1%) under one sun simulated solar radiation. Application of an electrolyte based on the [Co(bpy)3](2+/3+) redox couple and the MK2 organic sensitizer resulted in higher efficiencies (η = 7.70 ± 0.1%) than for the P25 devices (η = 6.3 ± 0.3%). Each performance parameter (short circuit current density, open circuit voltage and fill factor) was higher for the TiO2 nanobundle devices than those for the P25-based devices. The results of electrochemical impedance spectroscopy (EIS), intensity-modulated photovoltage spectroscopy (IMVS), and dye-loading measurements indicated that the better performance of TiO2 nanobundle devices with cobalt electrolytes correlates with higher porosity, relatively fast electron transport and more efficient suppression of electron recombination. A faster rate of diffusion of the cobalt complexes through the highly porous TiO2 nanobundle network is proposed to contribute to the enhanced device efficiency.
authors.affiliation: School of Chemistry, Monash University, Victoria 3800, Australia. leone.spiccia@monash.edu.
authors.forename: Cunku
authors.initials: C
authors.lastname: Dong
authors.forename: Wanchun
authors.initials: W
authors.lastname: Xiang
authors.forename: Fuzhi
authors.initials: F
authors.lastname: Huang
authors.forename: Dongchuan
authors.initials: D
authors.lastname: Fu
authors.forename: Wenchao
authors.initials: W
authors.lastname: Huang
authors.forename: Udo
authors.initials: U
authors.lastname: Bach
authors.forename: Yi-Bing
authors.initials: YB
authors.lastname: Cheng
authors.forename: Xin
authors.initials: X
authors.lastname: Li
authors.forename: Leone
authors.initials: L
authors.lastname: Spiccia
mesh_terms: D003035:Cobalt / Q000737:chemistry; D004396:Coloring Agents / Q000737:chemistry*; D056831:Coordination Complexes / Q000737:chemistry; D058266:Dielectric Spectroscopy; D004566:Electrodes; D004573:Electrolytes / Q000737:chemistry; D004583:Electrons; D049329:Nanostructures / Q000737:chemistry*; D010084:Oxidation-Reduction; D016062:Porosity; D012993:Solar Energy; D014025:Titanium / Q000737:chemistry*
chemical_list: D004396:Coloring Agents; D056831:Coordination Complexes; D004573:Electrolytes; C009495:titanium dioxide; D003035:Cobalt; D014025:Titanium