To reduce our reliance on fossil fuels and protect our planet, solar power must become more efficient and less expensive.
Right now, the dominant technology in the field, silicon-based solar cells, is too expensive to be widely adopted. Solar cells that use inorganic nanocrystals or “quantum dots” could be a cheaper alternative, but they are generally less efficient at turning solar energy into electricity.
Technion researchers have found a new way to generate an electrical field inside quantum dots, paving the way for more energy-efficient nanocrystal solar cells. Their findings were published in the October 9, 2011, issue of Nature Materials.
Professor Nir Tessler of the Zisapel Nanoelectronics Center in the Technion Department of Electrical Engineering and his colleagues have “tuned” the electrical properties of quantum dots before testing their capabilities in a model solar cell.
Such dots are promising materials for low-cost, high-efficiency solar cells due to their unusual electronic properties. For example, the size of a quantum dot correlates with its light absorption. Dots are each about one-millionth the size of the period at the end of this sentence, but changing a dot’s size can maximize its ability to harvest light within a solar cell.
To do that, the dots must share their electrons efficiently — a feat that has stymied researchers in the past. The Technion researchers’ findings suggest a new way to bring an electrical charge to dots by capping them with two different organic molecules. The chemical groups that attach the molecules to the dots’ surface generate the electrical field.
The findings give researchers one more method of controlling the building blocks of nanoelectronics. The dots are produced in an optoelectronic “ink” solution, and one day we may be able to print sheets of light or sheets of solar cells easily and cost-effectively.
Now, the researchers hope to combine the findings of this study with their previous work mixing different kinds of nanocrystals to determine whether mixing the methods leads to an even more efficient way of producing energy.
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