Dye-Sensitized Solar Cells: Their Promise and Practical Realities

Although the world is much more used to the deployment of solar systems that are based on modules built of semiconductor solid state PV cells, this technology is being challenged by emerging alternatives. Of the ones being touted as present, the one that seems to hold the greatest promise is the emergence of dye-sensitized solar cells. Though still undergoing development, these cells have caught the imagination of consumers and manufacturers alike from their colorful hues. They are also more transparent, flexible and thinner.

The approach used in development of the cells is distinctly different from that which is adopted for crystalline cells. While the task of absorption of light and carrying the charge from the cell for application is done by the solid state semiconductor material in traditional cells, this is done by separate components in dye sensitized solar cells. This is an approach that was pioneered by Michael Gratzel and these cells are still popularly known as Gratzel cells.

Even if there has been many attempts to improve on the efficiency of these cells, a good number of the attempts have come to naught. Even under laboratory conditions where many of the factors can be controlled, the capacity of the cells still remains lower than that of conventional cells. However, because materials used are so cheap in comparison, researchers are deep at work looking for more viable deployment of the cells. One of the most promising approaches is limiting the usage of such materials like Ruthenium or Platinum that drive costs significantly.

A dye sensitized solar cell is composed of three main components. The first is the sensitizing dye, a titanium nanoparticle layer and a liquid electrolyte. The electrolyte most often used is an iodide/tri-iodide redox couple) This electrolyte redox couple is crucial as it has direct implications on the amount of voltage that the cell is capable of generating.

Despite many attempts to improve effectiveness, the best DSCs have not achieved efficiencies to exceed about 12%. This has meant that modules made from Gratzel cells remain on the periphery of renewable energy applications, proving only capable of powering devices that have little demands on energy. However, there are some newer dyes being developed at present that promise to drive the capacity of these modules to give conventional panels a run of their money.

Gratzel cells absorb up to 85% of visible light but are terribly inefficient when it comes to the near-infrared section of the light spectrum. With emerging alternative dyes that can absorb up to 900 nm in the near-infrared sector, the power conversion efficiency of the DSCs can be increased by up to 14%. This value can be raised even further by replacing the liquid electrolytes with plastic solid state "hole conductors".

In terms of practical advantages, dye-sensitized solar modules share with other thin-film technologies the advantage of efficiencies even in high temperatures as they easily radiate extra heat easily than crystalline cells encased in protective glass. Due to what has been explained as better "differential kinetics", DSCs are able to operate efficiently even in low-light conditions. This factor is considerable enough to the extent that there are light-weight development of modules to power small devices even indoors.


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