One step to solar-cell efficiency: Researchers' chemical process may improve manufacturing

June 19, 2014
Rice University scientists have reduced to one step the process to turn silicon wafers into the black silicon used in solar cells. The advance could cut costs associated with the production of solar cells. Here, a cross section shows inverted pyramids etched into silicon by a chemical mixture over eight hours. Credit: Barron Group/Rice University

Rice University scientists have created a one-step process for producing highly efficient materials that let the maximum amount of sunlight reach a solar cell.

The Rice lab of chemist Andrew Barron found a simple way to etch nanoscale spikes into silicon that allows more than 99 percent of sunlight to reach the cells' active elements, where it can be turned into electricity.

The research by Barron and Rice graduate student and lead author Yen-Tien Lu appears in the Royal Society of Chemistry's Journal of Materials Chemistry A.

The more absorbed by a solar panel's active elements, the more power it will produce. But the light has to get there. Coatings in current use that protect the active elements let most light pass but reflect some as well. Various strategies have cut reflectance down to about 6 percent, Barron said, but the anti-reflection is limited to a specific range of light, incident angle and wavelength.

Enter , so named because it reflects almost no light. Black silicon is simply silicon with a highly textured surface of nanoscale spikes or pores that are smaller than the . The texture allows the efficient collection of light from any angle—from sunrise to sunset.

Barron and Lu have replaced a two-step process that involved metal deposition and electroless chemical etching with a single step that works at room temperature.

Rice University scientists have reduced to one step the process to turn silicon wafers into the black silicon used in solar cells. The advance could cut costs associated with the production of solar cells. Here, a top-down view shows pyramid-shaped pores etched into silicon over eight hours. Credit: Barron Group/Rice University

The chemical stew that makes it possible is a mix of copper nitrate, phosphorous acid, and water. When applied to a silicon wafer, the phosphorous acid reduces the copper ions to copper nanoparticles. The nanoparticles attract electrons from the silicon wafer's surface, oxidizing it and allowing hydrogen fluoride to burn inverted pyramid-shaped nanopores into the silicon.

Fine-tuning the process resulted in a black silicon layer with pores as small as 590 nanometers (billionths of a meter) that let through more than 99 percent of light. (By comparison, a clean, un-etched silicon wafer reflects nearly 100 percent of light.)

Barron said the spikes would still require a coating to protect them from the elements, and his lab is working on ways to shorten the eight-hour process needed to perform the etching in the lab. But the ease of creating black silicon in one step makes it far more practical than previous methods, he said.

Explore further: Emission peculiarities of high-quantum yield silicon nanoparticles

More information: J. Mater. Chem. A, 2014, Accepted Manuscript. DOI: 10.1039/C4TA02006E

Related Stories

Sunlight generates hydrogen in new porous silicon

April 10, 2014

Porous silicon manufactured in a bottom up procedure using solar energy can be used to generate hydrogen from water, according to a team of Penn State mechanical engineers, who also see applications for batteries, biosensors ...

Scientists come up with method of reducing solar panel glare

April 16, 2014

The glare from solar farms could be a thing of the past, thanks to scientists at Loughborough University. Researchers have developed a multi-layer anti-reflection (AR) coating for glass surfaces, which reduces the sun's reflection ...

Short nanotubes target pancreatic cancer

June 5, 2014

(Phys.org) —Short, customized carbon nanotubes have the potential to deliver drugs to pancreatic cancer cells and destroy them from within, according to researchers at Rice University and the University of Texas MD Anderson ...

Recommended for you

Meet the high-performance single-molecule diode

July 29, 2015

A team of researchers from Berkeley Lab and Columbia University has passed a major milestone in molecular electronics with the creation of the world's highest-performance single-molecule diode. Working at Berkeley Lab's Molecular ...

Could stronger, tougher paper replace metal?

July 24, 2015

Researchers at the University of Maryland recently discovered that paper made of cellulose fibers is tougher and stronger the smaller the fibers get. For a long time, engineers have sought a material that is both strong (resistant ...

Reshaping the solar spectrum to turn light to electricity

July 28, 2015

When it comes to installing solar cells, labor cost and the cost of the land to house them constitute the bulk of the expense. The solar cells—made often of silicon or cadmium telluride—rarely cost more than 20 percent ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.