Sensitization of monolayer transparent TiO2 thin films with metal-porphyrin dyes for DSSC applications. Equilibrium and kinetic aspects.

For the best manufacture of dye-sensitized solar cell (DSSC) systems (Figure 1), optimum objectives are represented from very rapid and complete adsorption of single layer of dye on the semiconductor surface [1,2]. Cu(II) and Zn(II) complexes of Coproporphyrin-I or CPI (Figure 2), has been synthesized in our laboratory and tested as sensitizers in DSSC devices [3,4]. A systematic study of kinetic and equilibrium for the adsorption of metal-CPI-dyes onto TiO2 monolayer surfaces, have permit to establish the best experimental conditions for the adsorption of these dyes and have demonstrated that the metal-CPI-dyes, according to the Langmuir model and with pseudo first-order kinetics, are adsorbed effectively in the support of TiO2 monolayer without chemical changes. The suppression of the dyes aggregation have permitted the optimization of selective adsorption of one layer of dyes molecules to stoichiometric ratios improving performances in DSSC indicating therefore a powerful experimental strategy, that can be enlarged to other dyes.