Aluminum oxides as alternative building blocks for efficientlayer-by-layerblocking layers in dye-sensitized solar
Lucas L Nascimento1, Jessica G Brussasco1, Igor A Garcia1
1Laboratory of Photochemistry and Materials Science-LAFOT-CM, Instituto de Química, Universidade Federal de Uberlândia, 38400-902 Uberlândia, MG, Brazil.
Abstract:
All inorganic layer-by-layer (LbL) thin films composed by TiO2nanoparticles and [Al(OH)4]-anions (TiO/AlO) as well as Al2O3and Nb2O5nanoparticles (AlO/NbO) have been deposited to fluorine-doped tin-oxide coated glass (FTO) surfaces and applied as blocking layers in dye-sensitized solar cells (DSCs). Structural and morphological characterization of the LbL films by different techniques reveal that inTiO/AlOassembly, aluminate anions undergo condensation reactions on the TiO2surface leading to the formation of highly homogeneous films with unique optical properties. After 25 depositions transmittance losses below 10% in relation to the bare FTO substrate are observed. Electrochemical impedance spectroscopy shows thatTiO/AlOlayers impose an effective barrier for the charge recombination at FTO/electrolyte interface with an electron exchange time constant 50-fold higher than that for bare FTO. As a result, an improvement of 85% in the overall conversion efficiency of DSCs was observed with the employment of TiO2/AlOxblocking layers.AlO/NbOLbL films can also work as blocking layers in DSCs but not as efficient, which is associated with the poor homogeneity of the film and its capacitive behavior. The production of cost-effective blocking layers with a low light scattering in the visible region is an important feature toward the application of DSC in other Building-integrated photovoltaic applications.
