Dye solar cells: a different approach to solar energy

Abstract

An attractive and cheaper alternative to siliconbased photovoltaic (PV) cells for the conversion of solar light into electrical energy is to utilise dyeadsorbed, large-band-gap metal oxide materials such as TiO2 to absorb the solar light. These devices, known as dye solar cells (DSCs), have a visible difference to conventional PV cells, in that they are semi-transparent. Hence they could be installed in place of glass windows in buildings and perform the dual tasks of providing shade for the occupants of the building and generating electricity. Our research includes the synthesis of TiO2 nano particles, the synthesis of a specific ruthenium dye, the preparation of the screen printable TiO2 paste and the assembly of complete cells ready for testing. Further research includes the testing of cells under reverse bias to determine the extent to which cells recover from adverse operating conditions, a characteristic that will be essential for the commercial application of the cells. In addition to chemical analysis, techniques such as impedance spectroscopy (Nyquist and Bode plots), cyclic voltammetry and I-V measurements by means of a PC-interfaced solar simulator are used to determine the stability of the cells. Further work includes research into the improvement of the efficiency of DSCs by utilising nanotechnology (TiO2 nanotubes). DSCs also generate electricity in diffuse light, i.e. cloudy days and in the shade. Results published by Japanese researchers (Toyoda et al., 2006) lead to comparative studies being conducted under South African conditions between DSCs and conventional silicon-based PVs. They found that the DSCs outperformed the crystalline silicon cells by ~20% per month over a six-month period, even though the DSC has a lower peak efficiency (~7.5 % vs. 15 %)