Caracterização fotoeletroquímica de dispositivos para conversão de energia solar

Abstract

This work is focused on the photoelectrochemical characterization of dye-sensitized TiO2 solar cells (DSCs), thin films of Al2O3/Nb2O5 and photoelectrochemical cells applied in the water splitting for fuel production (PECs). The thin films were applied as contact/blocking layer in DSCs. The synthesis of the oxides was done by the sol-gel method, the films were deposited by the self-assembly technique, from Al2O3 (pH ≅ 2) and Nb2O5 (pH ≅ 10). The presence of bilayers generated a 14% increase in overall DSC efficiency. Images of Atomic Force Microscopy (AFM) and Field Emission Scanning Electron Microscopy (FESEM) showed that the films are composed of spherical nanoparticles with homogeneous diameters, covering the entire surface of the conducting glass substrate coated with a conductive layer of fluoride-doped tin oxide (FTO), forming, thus, compact and few porous films. The films also presented higher average roughness (RMS) than the FTO without the bilayers, which increases the contact between the mesoporous TiO2 and the FTO surface, thus increasing the efficiency of the solar cells. Electrochemical Impedance Spectrometry (EIS) studies have shown that these films act to decrease recombination at the mediator/FTO interface. For the PECs, the Incident Photon to Current Efficiency (IPCE) was determined, which showed that there is a significant variation in its quantum efficiency, as a function of its chemical composition. Cells with W(VI) doped BiVO4/Bi4V2O11 films showed IPCE of up to 4.5%, while films that were not doped showed up to 1.5% IPCE.