Abstract:
The dye-sensitized solar cell (DSC) is a third generation photovoltaic device that holds significant promise for the inexpensive conversion of solar energy to electrical energy, because of the use of inexpensive materials and a relatively simple fabrication process. Most of the researchers in this field use Ruthenium complex as dye in these DSCs. However, Ruthenium is a rare metal, therefore, ruthenium-based compounds are relatively expensive. In this work, we explore the use of natural dyes obtained from various fruits, flowers and plants from Sri Lanka in these solar cells aiming to use these cells in low power and low cost biocensing applications. DSCs sensitized with several natural dyes extracted from fruits, leaves and flowers, showed photocurrent densities (Jsc) and photovoltages (Voc) ranging from 4.312 to 0.036 mAcm-2, and from 595.9 to 370.3 mV under the illumination of 100 mWcm-2 respectively. The corresponding efficiencies were ranged from 1.022 to 0.011%. While the DSSCs sensitized by acidified (pH<1) Begonia extracts showed the best cell performances giving a Jsc of 4.312 mA cm-2, with 428.7 mV photo voltage and an efficiency of 1.022%, the cells sensitized with acidified lxora coccinea delivered 2.126 mA cm-2 and 435.1mV as a photocurrent density and photovoltage respectively, with an efficiency of 0.446% under the above illumination. The maximum light absorption wavelength of the begonia dye found to be was around 522 nm and incidentally it was very close to the absorption peak position of the commercially available successful Ru (N3) dye. This peak position was red shifted to the higher wavelengths giving enhanced photocurrent out puts due to the acidification of the dye solution. The calculated energy gap between the Highest Occupied Molecular Orbital (HOMO) and Lowest Unoccupied Molecular Orbital level (LUMO) for the dye extracts obtained from Begonia was 2.25 eV.
Key Words: Dye sensitized solar cell, Natural dyes, Low cost, acidified Begonia extracts, lxora coccinea
