Scientific breakthroughs make solar cheaper

This summer's climate-related weather events have been a real eye-opener for those concerned about the pollution of our planet. Premature deaths have been occurring at an alarming rate due to the oppressive heat. Countries like Japan and Canada are experiencing heat waves that are unprecedented. Catastrophic wildfires have engulfed parts of California and Arizona and the fire season is far from over.  At the end of one of the hottest summers on record, as battles about how to power our world rage, solar energy continues to present an option that does not add greenhouse gases to the environment in exchange for lighting and cooling our homes. Solar has just been given another edge through material science. In a new study published in Energies, researchers have found a way to reduce production costs of solar cells by more than ten percent.

"Improving cost per unit power at the cell level can have massive effects downstream," says Joshua Pearce, professor of material sciences and electrical engineering at Michigan Tech. Already, he says, costs of solar energy are very close to conventional forms of electricity and is the fastest growing energy source. This ten percent drop should push solar to the forefront even faster.

Switching the silicon used in solar cells

Silicon is the active light-capturing material used in solar photovoltaic (PV) cells. It comes in two main forms: perfect crystals that cost more and produce higher efficiencies and multi-crystalline silicon that cost less, but offers lower efficiency. With common etching to reduce reflected light, both types still lose some light, which is what gives solar panels their blue color.

Researchers already knew that nano-texturing silicon with dry etching makes black silicon that is more efficient at gathering light than standard etching treatments. It has no color because the dry etching process takes a normally flat silicon surface and "etches it into a forest of nanoscale needles," Pearce says. "Those needles grab the light and don't let it get away. It's like looking into the eyes of Darth Vader."

Typically, such a high surface area with many surface defects would hurt electrical performance, but researchers at Aalto University found that when the silicon is also treated with an appropriate atomic layer deposition (ALD) coating, the effects of surface defects are somewhat reduced.

Typical thinking has been that the cost of black-Si cells from dry etching and ALD are too expensive for practical use, especially in an industry where, Pearce says, "margins are extremely tight. Everyone's trying to push costs as low as possible."

Still, the results of their study shocked even Pearce. While researchers did find that production of individual black-Si passive emitter rear cells (PERC) was between 15.8 and 25.1 percent more costly than making conventional cells, they also found that the efficiency gains and the ability to go to the less-expensive multi-crystalline silicon starting material far outweighed those extra expenses.  Overall the cost per unit power dropped by 10.8 percent.

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The future of solar energy production through material science

Black is better than blue when it comes to solar panels. The improvements could start to beat out renewables' top energy competitor in the climate change arena.

"For the people that think coal technology is going to be able to compete with solar, they should know solar costs are still coming down. Most coal companies are already, or near, bankrupt now," Pearce says. "There's no way coal's going to be able to compete with solar in the future."

He adds, "This study points to where the future is going to go in PV manufacturing and what countries might want to do to give themselves a competitive advantage."

Solar technological advances are making solar the choice today!