August 18, 2007
Silicon Nanocrystals Boost Photovoltaic Efficiency

Silicon nanocrystals can generate two electrons of energy from photons of ultraviolet and blue light.

A typical solar cell generates only one electron per photon of incoming sunlight. Some exotic materials are thought to produce multiple electrons per photon, but for the first time, the same effect has been seen in silicon. Researchers at the National Renewable Energy Laboratory (NREL), in Golden, CO, showed that silicon nanocrystals can produce two or three electrons per photon of high-energy sunlight. The effect, they say, could lead to a new type of solar cell that is both cheap and more than twice as efficient as today's typical photovoltaics.

This approach might achieve 40% efficiency of conversion. That's more than double what you'll find on the market today. (someone correct me if they know about commercial photovoltaic cells above 20% conversion efficiency)

By generating multiple electrons from high-energy photons, solar cells made of silicon nanocrystals could theoretically convert more than 40 percent of the energy in light into electrical power, says Arthur Nozik, a senior research fellow at NREL.

These researchers think silicon nanocrystals will be cheaper to make than multijunction photovoltaics that have achieved even higher efficiency. Given the multitude of approaches for achieving higher efficiency and lower costs our chances of getting cheaper photovoltaics seem high.

Cheap solar will some day make noon time the cheapest time to buy electricity. But will stationary battery storage ever become cheap enough to allow solar to compete for baseload demand?

Also see Boeing Spectrolab Achieves 40% Solar Cell Efficiency and Metamorphic Materials Increase Solar Photovoltaic Efficiency.

Update: Another report finds silicon nanoparticles improve solar cell efficiency.

CHAMPAIGN, Ill. — Placing a film of silicon nanoparticles onto a silicon solar cell can boost power, reduce heat and prolong the cell’s life, researchers now report.

“Integrating a high-quality film of silicon nanoparticles 1 nanometer in size directly onto silicon solar cells improves power performance by 60 percent in the ultraviolet range of the spectrum,” said Munir Nayfeh, a physicist at the University of Illinois and corresponding author of a paper accepted for publication in Applied Physics Letters.

A 10 percent improvement in the visible range of the spectrum can be achieved by using nanoparticles 2.85 nanometers in size, said Nayfeh, who also is a researcher at the university’s Beckman Institute.

In conventional solar cells, ultraviolet light is either filtered out or absorbed by the silicon and converted into potentially damaging heat, not electricity. In previous work, however, Nayfeh showed that ultraviolet light could efficiently couple to correctly sized nanoparticles and produce electricity. That work was reported in the August 2004 issue of the journal Photonics Technology Letters.

Share |      Randall Parker, 2007 August 18 09:12 PM  Energy Solar

Nick said at August 19, 2007 11:11 PM:

Probably, but we won't need it. Pumped water and PHEV's will probably work well enough.

This is a justification for diversity in energy supply. Wind tends to pickup during bad
weather, during the night and winter: it's somewhat inversely correlated with solar. Nuclear, of course, is pretty flat, and is a pretty good element of a diverse supply.

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