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Light Absorbing Dyes or Dye-sensitized Solar Cells (DSSCs)

Light absorbing dyes are one of the newest forms of photovoltaic panel currently under development. The concept relies on the fact that a semiconductor can be formed between an anode that is sensitive to photons and an electrolyte. In essence, this is a photoelectrochemical system with some similarities not only to other solar panels, but also to standard batteries.

The discovery that certain organic dyes (chlorophyll from spinach being one of the first) can generate electricity when exposed to light in the presences of oxide electrodes was the discovery necessary to make DSSCs possible. The construction is as follows.

A layer of organic dye overlies titanium dioxide crystals that are suspended in an electrolyte solution. An anode and cathode, as in a battery, are placed on either side of the electrolyte. When sunlight strikes the dye, electrons are excited to flow into the titanium dioxide solution. The electrons move toward the cathode where they are collected for powering an external circuit. Their trip is brought full circle when they are reintroduced to the electrolyte and then the dye molecules to engage in the process all over again.

Advantages and Efficiency

The major advantage of DSSCs is their low cost of manufacture and the fact that they can be produced on much larger scales than any type of crystalline or metallic semiconductor panel. When compared to thin film solar technology, DSSCs are more efficient in extracting energy from sunlight on a cost per watt basis. Even though overall efficiency currently stands at around 11%, the reduced cost of these panels makes them cheaper to operate on a kilowatt-hour basis.

Disadvantages

The major drawback to DSSCs is the liquid electrolyte that is necessary for their operation. It is extremely temperature sensitive and can even freeze, rendering it useless. There is current investigation into the use of solid electrolytes, but these many be more expensive to manufacture which will offset the cost per watt advantage that makes DSSC technology viable.
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