Low cost, efficient solar panels mimic plants

A new material design that mimics plants could make low-cost solar panels far more efficient by greatly enhancing their ability to collect the Sun's energy and release it as electricity, scientists say.
Researchers found that by assembling the components of the panels to more closely resemble the natural systems plants use to tap the Sun's energy, it may be possible to separate positive and negative charges in a stable way for up to several weeks compared to just millionths of a second - the current standard for many modern solar panels.
"In photosynthesis, plants that are exposed to sunlight use carefully organised nanoscale structures within their cells to rapidly separate charges - pulling electrons away from the positively charged molecule that is left behind, and keeping positive and negative charges separated," said Sarah Tolbert from the University of California, Los Angeles.

"That separation is the key to making the process so efficient," said Tolbert.
The team's X-ray studies at SLAC's Stanford Synchrotron Radiation Lightsource (SSRL) enabled them to see, at a microscopic level, which material design has the most ideal structure at the nanoscale for promoting this charge separation.
To capture energy from sunlight, conventional rooftop solar cells use silicon, which can be expensive.

Solar cells can also be made using lower-cost materials like plastics, but plastic cells are far less efficient - in large part because the separated positive and negative charges in the material often recombine before they can become electrical energy.

"Modern plastic solar cells don't have well-defined structures like plants do because we never knew how to make them before," Tolbert said.
"But this new system pulls charges apart and keeps them separated for days, or even weeks. Once you make the right structure, you can vastly improve the retention of energy," said Tolbert.
The new system is composed of strands of a polymer, the building block of plastics, that absorb sunlight and pass electrons to a fullerene, a spherical carbon molecule also known as a "buckyball."
The materials in these types of solar cells are typically organised like a plate of cooked pasta - a disorganised mass of long, skinny polymer "spaghetti" with random fullerene "meatballs."

But this arrangement makes it difficult to get current out of the cell because the electrons sometimes hop back to the polymer spaghetti and are lost.
The researchers figured out how to arrange the elements more neatly - small bundles of uncooked spaghetti with precisely placed meatballs.
The fullerenes inside the structure take electrons from the polymers and toss them to the outside fullerenes, which can effectively keep the electrons separated from the polymer for weeks.
The research was published in the journal Science.