Nanowire solar cells from CalTech

Three cheers for solar technology advancements!

This latest one comes from sunny Caltech (you might know it as California Institute of Technology).  Researchers there have created a new flexible solar cell, which takes long, thin silicon wires and embeds them into a polymer substrate.  The result is an inexpensive solar cell that can efficiently convert photons into electrons, using a tiny fraction of the semiconductor materials typically required for conventional solar cells.

According to Harry Atwater, director of Caltech’s Resnick Institute, which focuses on sustainability research:

“These solar cells have, for the first time, surpassed the conventional light-trapping limit for absorbing materials.  We’ve surpassed previous optical microstructures developed to trap light.”

When we refer to “light-trapping,” we’re talking about how much solar energy it is able to absorb from sunlight. The silicon-wire arrays in the new flexible solar cells can absorb up to 96% of incident sunlight at a single wavelength and 85% of total collectible sunlight.

As described in “Nature Materials:”

Many materials can absorb light quite well but not generate electricity — like, for instance, black paint.  What’s most important in a solar cell is whether that absorption leads to the creation of charge carriers.”

Specifically, the silicon wire arrays can convert 90-100% of the photons they absorb into electrons.  That means that the wires are exceptionally efficient!  When it comes to solar cells, you want both excellent absorption and conversion.

The result actually surprised the researchers a bit.  Notwithstanding sparseness of the wires in the array, a significant amount of light can be absorbed by the silicon wires which helps achieve both optical concentration and high efficiency of the silicon-wire-array solar cells.

The savings in cost are achieved through minimal use of expensive silicon materials.  The wires are only 30-100 microns in length and 1 micron in diameter.  Of that thin wire, only 2% is comprised of silicon.  The rest is polymer-based.  That means that the new flexible solar cells require only 1/50th of the amount of silicon of conventional solar cells.

On top of the savings in materials, manufacturing these solar cells is also cheaper than normal.  Flexible thin film panels can be created using a roll-to-roll process, which is much more cost-effective than creating brittle wafers used in ordinary cells.

What is the future for these new flexible solar cells?  Stay tuned for more information and news!