Photo-Electrical Conversion Efficiency Of Dye Sensitized Solar Cells Prepared From Mopane Leaf Chlorophyll Extract

ABSTRACT

In times of fossil fuel shortage, increasing crude oil prices, as well as rejection of conventional energy sources (e.g. coal or nuclear power plants), sustainable energy forms become more and more the focus of attention. One of several offered solutions is to develop a photovoltaic device (solar cells), since solar energy is abundant. Especially, Namibia receives solar radiation of 5.8 to 6.4 KWh per square meter per day – one of the highest in the world. With 8 to 11 average hours of sunshine per day throughout the year, this offers fantastic potential for solar energy, both photovoltaics and solar thermal. Dye Sensitized Solar Cell (DSSC) which is presented here is a thin film cell. Manufacturing of DSSCs is simple, mostly low cost, and incorporate environmentally friendly materials. They have a good efficiency (about 10-14 %) even under low flux of sunlight. However, a major drawback is the temperature sensitivity of the liquid electrolyte. Hence, this study presents the ongoing research to improve the electrolyte’s performance by using natural dye. A transparent conductive oxide (TCO) film of Fluorine - doped Tin Oxide (FTO) was used as an anode. In this research, chlorophyll extracted from Colophospermum Mopane leaves using methanol was employed as the dye for TiO2-based DSSC. TiO2 precursor solution prepared by Molecular precursor method (MPM) was spin-coated on top of Fluorine- Doped Tin Oxide (FTO) conductive glass and calcined at 420 ̊C for 20 min to act as an anode electrode. The cathode electrode was a supportive glass substrate coated with a layer TiO2 paste (Degussa P25) followed by graphene layer obtained from charcoals sold in Namibian markets. The anode electrode was then immersed in the dye for 20 min, to make the TiO2-chlorophyll thin film.