High efficiency dye-sensitized solar cells exploiting sponge-like ZnO nanostructures

Abstract

Sponge-like nanostructured ZnO layers were successfully employed as photoanodes for the fabrication of highly efficient dye-sensitized solar cells. The sponge-like ZnO layers were obtained by room temperature radio-frequency magnetron sputtering deposition of metallic zinc, followed by thermal oxidation treatment in an ambient atmosphere. The porous films show a 3D branched nanomorphology, with a feature similar to natural coral. The morphological and optical properties of these layers were studied through field emission scanning electron microscopy, specific surface area measurements, ultraviolet-visible transmittance and absorption spectroscopy. The sponge-like ZnO film presents a high density of branches, with a relatively high specific surface area value, and fine optical transmittance. The morphology of the porous structure provides a high number of adsorption sites for the anchoring of sensitizer molecules, making it suitable for the fabrication of ZnO-based photoanodes for dye-sensitized solar cells. The light harvesting performance of the sensitized semiconductor was evaluated by current density vs. voltage measurements, incident photon-to-electron conversion efficiency, open circuit voltage decay and impedance spectroscopy. The modelling of the electrical characteristics evidences a higher electron lifetime and a longer charge diffusion length, if compared to standard TiO(2) nanoparticle based photoanodes. For ZnO films with a thickness up to 18 μm, a photoconversion efficiency as high as 6.67% and a maximum value of the incident photon-to-electron collection efficiency equal to 87% at 530 nm were demonstrated.

Morphology induced light scattering by zinc oxide polydisperse particles: Promising for dye sensitized solar cell application

“…Table II compares the performance of the developed ZnO photo-anode (on FTO coated glass substrates) with the other ZnO based dye sensitized solar cell reported recently. 24,28,36,[38][39][40][41][42] For dye sensitized solar cell application, zinc oxide based photo-anode with various dyes and electrolytes has been reported. [29][30][31][32][33][34][35] However, the cells having significant solar to electric conversion efficiency (!2%) and prepared using N3/N719 dyes and I À /I 3 À electrolyte are considered for the present comparison.…”

Nanostructured ZnO Materials: Synthesis, Properties and Applications

“…In the field of solar energy harvesting, particularly for what concerns DSCs, photoanodes based on porous zinc oxide layers can provide photoconversion efficiencies as high as about 7 % [119,135,136], although TiO 2 -based photoanodes still give the best performances (with efficiencies over 11 % [137]). Many efforts have been dedicated by several research groups to the study of nanostructured ZnO-based DSC photoanodes, since ZnO electronic transport and mobility properties are more favorable to the correct DSC operation than those of TiO 2 , and, in addition, the advantage over TiO 2 , represented by the ease of synthesizing ZnO nanostructures with a variety of shapes, can help tuning such properties [137].…”

Toward quasi-solid state Dye-sensitized Solar Cells: Effect of γ-Al 2 O 3 nanoparticle dispersion into liquid electrolyte

“…TiO 2 layers with an average thickness of 8 lm were sensitized with N719, soaking them in 0.35 mM ethanol-based dye solution (Ruthenizer 535bis-TBA, Solaronix). Counter electrode fabrication and cell assembly procedures were reported in previous works (Lamberti et al, 2013;Sacco et al, 2012a). Synthetically, to prepare the counter electrodes, FTO-glasses were drilled to create an inlet port for the electrolyte filling, then cleaned as described above and Pt-coated (5 nm) by thermal evaporation.…”

“…The sealed cells were filled with the electrolyte following a vacuum procedure (Sacco et al, 2012a) and no difference in the filling step was observed by the addiction of the nanoparticles. In Fig.…”