Novel Comparative Study And Characterization Of Plant Dyes In Tio2 Matrix For Dye Sensitized Solar Cells Applications

ABSTRACT

A good energy mix is desirable for sustainability of the energy needs of many countries. Currently, electricity, including that sourced from photovoltaic cells is widely used for not only homesteads but also for industries. The desire to develop a cost-effective source of energy has motivated the development of dye sensitized solar cells. This technology has motivated a lot of research owing to its improved efficiency. This work has utilized plant extracts using a binder to develop a solar cell from locally available materials. Sieved extracts were obtained from carrot tubers, orange fruits and French marigold leaves. The juices extracted from each plant were stored in individual containers ready for sensitization. Ruthenium inorganic binder was used as a control. Screen printing technique was used to deposit titanium dioxide paste on the fluorine doped tin oxide glass slides. The developed thin films were annealed at a temperature of 450oC in a furnace after which they were removed and allowed to cool ready for optical and electrical characterization. Using a DUV 3700 spectrophotometer, optical transmittance peak results indicated that ruthenium dye was transmitting at a peak of 47%, orange dye was transmitting at a peak of 30%, and French marigold dye was transmitting at a peak of 11% while the carrot dye was transmitting at a peak of 8%. On mixing different combinations of dyes in the ratio 1:1 by volume, the optical transmittance peak results indicated that the combination of carrot dye and French marigold dye was transmitting at peak of 27%, carrot dye and orange dye was transmitting at peak of 40% while French marigold dye and orange dye was transmitting at peak of 42%. These were higher than the transmittance peak values for single dyes. This was attributed to surface interaction. For reflectance characterization, orange dye peak reflectance was 24%, carrot dye peak reflectance was 14% while French marigold dye peak reflectance was 8% and the control dye was 15%. For absorption characterization (still in the range using DUV), French marigold dye absorption peaked at 91%, carrot dye absorbed at a peak of 92%, orange dye absorbed at a peak of 85% while the ruthenium dye absorbed at a peak of 84%. Electrical characterization of the solar cell was based on open circuit Voltage (Voc) which was 0.482V for carrot dye, 0.433V for orange dye, 0.469V for French marigold dye and 0.565V for ruthenium dye. Short circuit Current (Isc) was 0.0092 mA for carrot dye, 0.0099 mA for French marigold dye, 0.010 mA for orange dye, and 0.195mA for Ruthenium dye. The fill factor was 69.0% for carrot dye, 69.35% for French marigold dye, 67.1% for Orange dye while ruthenium dye had 58.1%. The obtained efficiency showed that carrot dye had an efficiency of 0.10%, French marigold dye had 0.097%, and orange dye had 0.087% while the control dye had 1.032%. From the study it was concluded that of the organic dyes Carrot dye gave a better efficiency of 0.100% and the least efficiency by orange dye. Ruthenium dye had the best efficiency of 1.032%. This was attributed to its wide spectral absorption. In conclusion therefore, a dye made of carrots juice could be more reliable as it has a higher efficiency. We recommend the purification of carrot dye before use to improve its efficiency