Materials researchers achieve breakthrough for solar cells

A Colorado School of Mines PhD candidate in materials science is the lead author of a paper featured on the cover of Advanced Electronic Materials that details a breakthrough in the development of a material for solar cells.

Angela Fioretti’s “Solar Cells: Effects of Hydrogen on Acceptor Activation in Ternary Nitride Semiconductors” was published in the March 2017 issue of the journal. Coauthors were metallurgical and materials engineering postdoctoral researcher Adam Stokes, Physics Teaching Professor Matt Young, Physics Assistant Professor Eric Toberer—Fioretti’s advisor, Physics Research Assistant Professor Adele Tamboli and Andriy Zakutayev of the National Renewable Energy Laboratory.

The vast majority of solar panels are based on elemental silicon, which is a fundamentally inefficient light absorber. “Development of new semiconductors that absorb light better is therefore necessary for solar energy technology to reach its full potential,” the researchers said.

The researchers focused on a ternary nitride semiconductor known as zinc tin nitride, which absorbs sunlight much better than silicon but does not have well-controlled electrical properties. They found that by exploiting the presence of hydrogen during synthesis and removing it afterwards, they could control the electron concentration in the material, which is critical to solar cell design. The team also discovered that the technique was most effective in samples that contained excess zinc, as opposed to the usual method using equal amounts of zinc and tin.

This method of controlling electron concentration was inspired by a similar technique in binary nitrides, which are used in blue LEDs. “This shows that well-known processing tricks can be applied to shorten the development time of new nitride-based solar cell technologies,” the researchers said.

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