Successful conversion of visible light in electricity was achieved by blue-violet anthocyanins from Jaboticaba (Myrtus cauliflora Mart) and Calafate (Berberies buxifolia Lam) as TiO2 dye-sensitizers. The anthocyanins obtained by such extracts are capable to be chemically adsorbed onto semiconductor surface, sensitizing it to the visible region of the spectrum. The energy of the excited state of these dyes is also appropriate to promote the electron injection into the semiconductor conducting band, consequently, converting the sunlight into electrical output. The use of other natural sources of dye sensitizers demonstrate that only selected extracts promotes the energy conversion.
A preliminary test of stability of these solar cells showed that no decrease in the Jsc was observed for a Jaboticaba dye sensitized solar cell for 3 h irradiation. Further studies evaluating a long term stability are a subject to be focused.
The use of natural dyes can be an alternative for a lower cost production of dye- sensitized solar cells, being environmentally friendly renewable and clean source of energy. It is also useful to demonstrate several important scientific concepts (materials, semiconductors, molecular devices,etc.) for educational purposes