Influences of the deposition process on the properties of TiO2 blocking layer for Dye-Sensitized Solar Cells

Aim of this work was to asses the correlation between the most common deposition processes and the mophological and electrochemical properties of the blocking layers produced. The blocking layer of TiO2 was prepared on FTO glass using two of the most colloidal deposition processes: dip coating and spin coating. The results obtained with conventional dip coating process were compared with the ones coming from spin coating of two different solution (acqueos and alcoholic). The operating parameters were optimized on the basis of the compositional, optical, morphological, and electrochemical properties of the film obtained. The ethanol system allows the production of the most homogeneous, continuous and dense film and therefore in a decrease in dark current and a consequent increase in the cell efficiency. Finally, EIS (electrical impedance spectroscopy) and current voltage curves in the dark and under sun conditions (AM 1.5 and 1000 W m2) were carried out in order to separate the individual resistive contributions of the blocking layer and the efficiency on both cell and final device. These analyses allows to identify the best process and deposition parameters necessary to obtain an efficient blocking layer. Spin coating of an alcoholic solution was considered the most appropriate processes. An improvement of 2% of the cell efficiency was reached using the optimized layer.