Natural Dye-sensitized Solar Cells

A novel ternary-encapsulated spherical TiO2 (TES-TiO2) with submicron particle sizes was formed by blending commercial P25 TiO2 and two different sizes of TiO2 particles synthesized by modified sol-gel and hydrothermal methods. A double-layered TiO2 electrode for dye-sensitized solar cell (DSSC) was fabricated by depositing TES-TiO2 particles onto nanocrystalline mesoporous TiO2 (Meso-TiO2)-coated Fluorine-doped SnO2 glass (FTO) by a cathodic electrophoresis technique. Compared to double-layered Meso-TiO2/P25 electrodes, the energy conversion efficiency (η) of DSSC from the obtained Meso-TiO2/TES-TiO2 electrode was improved by 9.3%, from 5.94% to 6.49%. When the prepared double-layered Meso-TiO2/TES-TiO2 electrode was calcined at high temperature, a high-voltage electric field (HVEF) was introduced to assist crystallization. As a result,ηwas further enhanced by 8.6%, from 6.49% to 7.05%. Notably, compared to typical 20 run TiO2 nanocrystallites applied in the active layer of DSSC, the prepared loosely porous TES-TiO2 with submicron size increased the light scattering effect and promoted dye molecule adsorption and the diffusion of electrolytes.In addition, introduction of the HVEF provided better connection among TiO2 particles, which facilitated electron transport and avoided charge recombination.Study on DSSC with extracts of Canna indica L., Salvia splendens, Solanum nigrum L. as sensitizers is firstly reported in this paper. Solar cells were assembled by using natural dyes extracted from Canna indica L., Salvia splendens, cowberry and Solanum nigrum L. as sensitizers. The energy conversion efficiency of the cells sensitized with dyes of Canna indica L., Salvia splendens, cowberry and Solanum nigrum L. was 0.29%,0.26%,0.13% and 0.31%, respectively. We present FTIR and UV-vis spectroscopy studies of structures and light absorption of these four kinds of natural dyes. The electrochemical impedance spectroscopy (EIS) was used to analyze the interface resistance of cells. The result indicated that high resistance existed in the interfaces of cell with cowberry extract as sensitizer.