Alternative Energy

It is being estimated that the world demand for energy would be more than twice over by 2050 and we will still be clamoring for more than triple by the end of the 21st century. By that time stock of fossil fuels would be insufficient to meet the ever increasing demand. If we want to march ahead in future we have to seek answers for our energy requirements by using sustainable and carbon-neutral energy technologies. We have to depend on the use of sunlight to generate electricity as well as to split water molecules for the production of fuels. Nanocrystals could be crucial to the success of this vision. We know that electrical conductance in semiconductor nanocrystals is a decisive element for both solar electricity and solar fuel technologies.

Sustained advancements are visible in the field of semiconductor nanocrystals and the future of clean and green energy is holding promises. Researchers affiliated with the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) are working on a technique which will help in improving the electrical conductivity of nanorod crystals of the semiconductor by 100,000 times. These rods consist of cadmium-selenide.

Paul Alivisatos who is the interim-Director of Berkeley Lab, is leading this research. Alivisatos is an internationally-renowned figure on nanocrystal growth. He is a chemist who also holds joint appointments with Berkeley Lab’s Materials Sciences Division, and with the University of California-Berkeley. In the university he is the Larry and Diane Bock professor of Nanotechnology. He has also written a paper published in the online edition of NanoLetters entitled: “Enhanced Semiconductor Nanocrystal Conductance via Solution Grown Contacts.” Matthew Sheldon and Paul-Emile Trudeau are the co-authors of the paper too.

Paul Alivisatos shares his thoughts on his work, “The key to our success is the fabrication of gold electrical contacts on the ends of cadmium-selenide rods via direct solution phase-growth of the gold tips. Solution-grown contacts provide an intimate, abrupt nanocrystal-metal contact free of surfactant, which means that unlike previous techniques for adding metal contacts, ours preserves the intrinsic semiconductor character of the starting nanocrystal.”

Sheldon, who was the lead author on the NanoLetters paper explained about the technique, “Standard contacting procedures that deposit metal onto semiconductor nanocrystals directly, such as those used in commercial wafer-scale chip fabrication, cause alloying and chemical reactions at the metal-semiconductor interface. This means that the finished electrical device is actually made of a different material than the starting nanocrystal.”

Alivisatos, compares his work with the existing works, “Our study shows that the superior performance of gold-tipped cadmium-selenide heterostructures results from a lower Schottky barrier and that solution grown contacts do not alter the chemical composition of the semiconductor. Further, our work demonstrates the increasing sophistication of high-quality electrical devices that can be achieved through self-assembly and verifies this process as an excellent route to the next generation of electronic and optoelectronic devices utilizing colloidal nanocrystals.”

Sheldon emphasized further, “We believe our approach is an ideal strategy for making future devices from nanocrystals because it preserves the semiconductor character of the nanocrystal as synthesized with the precise control of their synthesis developed over the past decades.”

Sheldon is familiar with the ground reality. He knows he has to test his success in laboratory on commercial scale too. His next move would be to establish if the remarkable improvements in electrical behavior can translate to improvements in nanocrystal-based energy production.

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