Front-side illuminated dye-sensitized solar cells based on bundle shaped titania nanotube membranes

TiO2 nanotubular (NT) membranes with bundle shape morphology were prepared by rapid breakdown anodization (RBA) in fluorine free aqueous electrolytes. The self-assembled nanotube-like materials were detached from the metal foil by immersion in methanolic Br-2 solution and the free-standing membranes were successfully transferred on top of transparent conductive electrodes modified by freshly prepared nano-particulate (NP) titania films. The composite electrodes, after post-annealing at 450 degrees C, were crystallized under the anatase polymorphism and, then, effectively sensitized by the standard N719 dye (confirmed by micro-Raman spectroscopy under Resonance conditions). The resulting photoelectrodes were incorporated in dye-sensitized solar cells (DSCs) enabling front-side illumination (FSI). The fabricated DSCs attained overall photovoltaic conversion efficiencies of the order of 4.6% under 1 sun (AM 1.5) illumination. The relatively high performance was mainly attributed to the successful packing of the two (NT and NP) layers creating a low resistance interface as well as to the favourable electron transport/recombination dynamics that govern these solar cells. [GRAPHICS] (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim