Technical Digest of the International PVSEC-14, Bangkok, Thailand 2004 LP1-024 Using Porphyrin and Eosin y as Electron Donor in Dye Sensitized Solar Cells

Preparation of the (SnO2) conducting glass. The DSSC produced in this work was prepared from kale-porphyrins derivatives, the cell composed of TiO2-dye conducting anode and SnO2 counter electrode(CE).However,under the sun light at noon Eosin y with SnO2-activated carbon CE showed higher short circuit current(Isc) and open circuit potential(Voc). A solution of 40 g SnCl4 in 50ml of methanol was heated at 50 °C for 5 min. then 0.9g NH4F was added. The solution was sprayed on a glass slide which was preheated to 400 °C. Preparation of TiO2 1. General Introduction 125 ml of titanium iso-orthotitanate was added to 750 ml of 0.1 M HNO3 with stirring then the slurry obtained was heated to 80 °C and left evaporated after stirred for 8 hrs. When a DSSC(dye sensitized solar cells) is illuminated by sunlight, the dyes absorb the light and become excited. The absorption of light by the dyes is followed by the injection of an electron from the excited state of the dye to the conduction band of the semiconductor. Simultaneously the oxidized dye is reduced by the electron donor in the electrolyte and returns to the ground state. The electrons in the conduction band of the semiconductor are collected at the back contact electrode and flow through the external circuit. These electrons arrive at the counter electrode and have an effect on the reverse reaction of the redox couple. Through these processes, radiant energy is converted into electricity [1].This research aimed to fabricate the dye sensitized solar cell by used of natural porphyrin derivative and Eosin y as the sensitizers and measured the short circiut current and opencirciut potential of the solar cells. Preparation of electrode (the anode) 10 g of nanocrystalline TiO2 was ground and spreaded on the conductiong glass by silk screen in the form of paste TiO2.The coated glass was dried in air for 30 min. and left to cool down after sintered at 450 °C for 30 min. It was then soaked by the dye solution (10mg dye in 10 ml methanol) over night. The soaked plate was placed up and the I/I2 electrolyte solution was dropped on. Another conductiong glass as the counter electrode was put on the top of the soaked plate filled with I/I2 solution to form the DSSC. Measument of short circuit current and open circiut potential This was done by exposing the DSSC to the sunligh at noon which was accepted that the intensity of the sunlight is 1000 mW/cm. 2. Experimental details Preparation of porphyrin derivatives. Chlorophyll was isolated from kale by methanol and was partially purified by dioxane method. Chlorophyll was separated by chromatographic method. Chlorophyll obtained was refluxed with dry HCl for 2 hrs,cooled down and diluted with ether.Then Mg ion was removed by extracting the solution with 10 % HCl, Metallo-methylpheo phorbide (dye) was obtained by adding transition metal salt solutions of Ni, Co, Cu, Zn into the solution of the extract.These complexes was characterized by UV-Vis spectrophoto-metry and elemental analysis. The improvement of DSSC by Using Eosin y as dye and modified counter electrode. Eosin y was used to replace the metallo metylpheophorbide a from the reason that the porphyrin derivatives prepared from kale and transition metal salt solutions were not stable and Isc,Voc might not be reproducible. The counter electrode for the electron flow through the circuit was also improved by mixing the activated carbon into the SnCl4 solution at the conducting glass preparation process.