Working at the frontiers of photonics and nano-scale semiconductor fabrication, an international team of researchers from universities and laboratories in Sweden, Switzerland, Spain, and the US have “demonstrated a process whereby quantum dots can self-assemble at optimal locations in nanowires, a breakthrough that could improve solar cells, quantum computing, and lighting devices,” according to a February 8 NREL press release.
Reproducing breakthrough research undertaken by Swiss scientists, US National Renewable Energy Laboratory (NREL) senior researcher Jun-Wei Luo made use of NREL’s supercomputer to demonstrate a “quantum-dot-in-nanowire” system that “raises a huge potential for their use in detecting local electric and magnetic fields. The quantum dots also could be used to charge converters for better light-harvesting, as in the case of photovoltaic (PV) cells.”
Harnessing Quantum Photonic Properties
Quantum dots are tiny particles of semiconductor material typically ranging from 2 to 10 nanometers (10-9 meters) in diameter, about as wide as 50 atoms. Their small size imbues them with “unique optical and electrical properties that are different in character to those of the corresponding bulk material.” Producing just a kilogram of such material would be sufficient to feed manufacturing at commercial scales, explains nano engineering research and development company Nanoco Group Plc.
“At that size they exhibit beneficial behaviors of quantum physics such as forming electron-hole pairs and harvesting excess energy,” NREL adds.
NREL researchers late last October announced they had developed quantum dots and used them to fabricate solar PV cells that broke through a previously accepted barrier limiting the amount of electrical energy they are capable of producing from photons. The quantum dot solar PV cell they created was able to produce 30% more electric current from blue-light-frequency-range photons than the current generation of commercial PV cells.
“While traditional semiconductors only produce one electron from each photon, nanometer-sized crystalline materials such as quantum dots avoid this restriction and are being developed as promising photovoltaic materials,” a news release from AVS: Science and Technology of Materials, Interfaces and Processing explained.
“An increase in the efficiency comes from quantum dots harvesting energy that would otherwise be lost as heat in conventional semiconductors. The amount of heat loss is reduced and the resulting energy is funneled into creating more electrical current.”
Detailed in “Self-assembled Quantum Dots in a Nanowire System for Quantum Photonics,” published in the current issue of the journal Nature Materials, the quantum dots developed by NREL and the international team of researchers self-assemble at the interface of the “apex of the gallium arsenide/aluminum gallium arsenide core” and nanowire shell.
The ability to position these highly stable quantum dots so precisely means that manufacturers would be able to take full advantage of the “materials’ ability to provide quantum confinement for both the electrons and the holes,” turning the approach into “a potential game-changer.”
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