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Experiment 3 Solar Cells from Natural Dyes Adapted from Smestad G P Gr tzel M J Chem Ed 1998 75 753 Introduction Scientists are very interested in building inexpensive and effective solar cells Current solar technology uses silicon an element that is abundant but expensive to process In these cells silicon absorbs light and converts it to electrons An alternative to the silicon solar cell is one made from natural dyes that can also absorb light and convert it to electrons Natural dyes may not be as efficient as silicon cells but they are much less expensive to produce These natural dyes contain colored chemical compounds known as anthocyanins These compounds are what give many fruits and vegetables their distinct colors This includes blackberries strawberries raspberries and even the deep red and orange colors of autumn leaves Anthocyanins attach themselves very well to oxide materials such as titanium dioxide titania due to a number of hydroxyl OH bonds on both the titania and the dye When electrons are produced by the dye they conduct themselves through the molecule and into the titania As long as the titania film is bound to a conductive surface we can harness those electrons to do useful work such as power a light bulb As the adage goes however you cannot get something for nothing The dye molecule cannot produce an endless supply of electrons and they must be regenerated By using an electron donor or redox electrolyte the electrons are supplied back to the dye Of course this electrolyte does not have an unlimited supply of electrons either The electrolyte receives its electrons from the return of the dye generated electrons that were sent through the circuit This cycle is important electrons are never used up or destroyed the power is just used to do some amount of work This whole device dye titania and electron donor complex creates what is known as a dye sensitized solar cell or DSSC This type of cell was invented and published by Michael Gr tzel in the

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