|
|
Tuesday November 6th 2007 Every 2 years the Royal Society of Chemistry holds a “Chemistry Week”, to encourage interest in the subject. For our Chemistry week lecture we welcome: Prof Laurence Peter of Bath University where he leads the electrochemistry group |
|
 |
|
Low cost solar cells
Notes on a talk at Café Scientifique in Salisbury Arts Centre given by Chemistry Professor Laurie Peter of Bath University during national chemistry week (6/11/7).
After reminding us of the greenhouse effect and the need for more renewable energy, which is still lamentably little in the UK , Professor Peter showed us nature's solution. Leaves are inexpensive, flexible electron pumps. His group at Bath University are to produce light flexible solar cells in a way inspired by photosynthesis. Meanwhile, G24 Innovations, a new company in Wales , are already producing flexible solar cells to power mobile phone chargers
The resulting Gratzel Cell produces ¾ of a volt so 6 cells together produce a useful 4.5 volts. And there is a usable current even in low light.
In the interval, Laurie Peter made us a working example using raspberries as the dye and it produced half a volt from the overhead projector lamp. Whilst he was playing chemistry with raspberries and iodine, I briefly flicked off the projector and sure enough the demo solar cell that he set up earlier, did stop turning the rotor it was powering.
In the concluding questions and answers session, we learnt that the efficiency of these cells is less than with silicon (about 10% rather than say 15% for silicon). But the cost and energy required for production is so much less that the efficiency and life (perhaps 5 or 10 years) are not as limiting to usefulness. Initial applications are mainly for charging mobile devices, and soon, as materials to go on the roof of a house or car. We came away re-inspired by chemistry, entertained and gladdened by a developing British success story.
Michael Stroud
|
|
Most solar cells today use silicon which is expensive, uses a large amount of electricity to produce. So instead of using silicon, dye-sensitized solar cells use cheap titanium dioxide, a main ingredient of toothpaste. A dye captures photons, pumping electrons to the titanium dioxide which are passed onto a conducting layer deposited on rigid glass or a flexible roll. A ‘refresher' such as iodide, refreshes the dye with electrons returning via the other conducting layer to complete the circuit.