title: 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.
authors.affiliation: Center for Space Human Robotics @PoliTo, Istituto Italiano di Tecnologia, Corso Trento 21, 10129, Turin, Italy. adriano.sacco@iit.it
authors.forename: Adriano
authors.initials: A
authors.lastname: Sacco
authors.forename: Andrea
authors.initials: A
authors.lastname: Lamberti
authors.forename: Rossana
authors.initials: R
authors.lastname: Gazia
authors.forename: Stefano
authors.initials: S
authors.lastname: Bianco
authors.forename: Diego
authors.initials: D
authors.lastname: Manfredi
authors.forename: Nadia
authors.initials: N
authors.lastname: Shahzad
authors.forename: Federica
authors.initials: F
authors.lastname: Cappelluti
authors.forename: Shuai
authors.initials: S
authors.lastname: Ma
authors.forename: Elena
authors.initials: E
authors.lastname: Tresso