In recent years, nanotechnology researchers are achieving astonishing results in many fields of medicine and electronics: from microscopic sensors to transistors constantly decreasing in size, industry is pushing to innovate and find always new, cost-effective solutions. One of the most promising and exciting progress has been shown in the field of solar cells development.
How Traditional Solar Cells Work
A solar cell is quite a complex piece of electronics, and a full understanding of its working mechanism requires advanced knowledge of both physics and chemistry.
To simply put it, two silicon layers with opposite polarization -- p and n, positive and negative -- are placed alongside: whenever a ray of light hits the external part of the cell, the energy frees the chemical bounds of both an electron and the corresponding electronic hole left by it.
Thanks to the electric field resulting from the junction between the positive and negative layer of the cell (p-n junction), the electron will tend to approach the n layer, while the hole will tend to approach the p layer (see Figure 1). This movement of charges in an opposite direction generates an electric current which can be easily exploited to produce electric power.
The main efficiency drawback in a traditional solar cell is due to the fact that, once freed, both electrons and holes tend to reach their destination very slowly, particularly if the pair is initially very far from the electric field.
The resulting trajectory is almost a casual one, because the density of the surrounding material causes the particles to continually collide and bounce back. Typical efficiency values for domestic use solar cells are up to 20%, and around 28-30% for satellite technology, which has a higher cost per watt.
How Nanotech Solar Cells Work and Ongoing Research
The so-called third generation of solar cells is a currently active and vibrant research field of nanotechnology which is predicted to bring incredible innovations on the market in the near future.
One of the most promising ideas has been advanced by Stanford Assistant Professor Yi Cui. His approach includes using carbon nanowires and nanocrystals solved in an organic solution, which is then sprinkled onto the glass layer forming the external portion of the cell.
As a result, polymer and crystals will form a myriad of microscopic p-n junctions that can separate electrons and holes with a mechanism very similar to that of traditional cells, but in which the much shorter distance the particles have to cover implies a significantly higher efficiency of the cell.
Cui's approach currently results in more efficient and significantly cheaper solar cells, however he himself states that his research in the field is just at the beginning and that more innovations are to come in the next future.
References and Further Readings
E. Lorenzo, " Solar Electricity: Engineering of Photovoltaic Systems " (Progensa), 59-70
S. Meister, C. K. Chan, H. Peng and Y. Cui, "Nanowires for Nanoscale Electronics, Biosensors and Energy Applications"
Dario Borghino - Dario Borghino is a young Italian freelance writer, translator, and computer programmer. Follow him on Twitter at: twitter.com/outspan.
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