UCLA Chemists Create Solar Cells Capable of Retaining Energy for Weeks

Tuesday, 23 June 2015 - 11:31AM
Tuesday, 23 June 2015 - 11:31AM
UCLA Chemists Create Solar Cells Capable of Retaining Energy for Weeks
The hunt for sustainable energy is on; UCLA chemists have just published research pertaining to a new design for a plastic that is capable of storing solar energy for up to several weeks, which could revolutionize the solar power industry.

The design was inspired by the way plants generate energy from photosynthesis. "In photosynthesis, plants that are exposed to sunlight use carefully organized nanoscale structures within their cells to rapidly separate charges... that separation is key to making the process so efficient," explains Sarah Tolbert, UCLA professor of chemistry and one of the senior authors of the research. 

Up until now, conventional rooftop solar cells used silicone, a fairly expensive material which led to difficulties in lowering the costs associated with solar energy, and made the technology inaccessible to many people. The cheaper plastic alternatives on the market are relatively inefficient, mostly because the separated positive and negative charges often recombine before they become energy. 

Toldbert's team has managed come up with a way to combat this inefficiency by using two components, a polymer donor and a nano-scale fullerene acceptor. A fullerene, is a molecule of carbon in the form of a hollow sphere, tube, or other shape. The polymer donor absorbs sunlight and passes electrons to the fullerene acceptor, which then generates energy. "This new system pulls charges apart and keeps them separated for days, or even weeks," says Tolbert.

Previous plastic solar cells have contained this same technology, but the two parts were thrown together in a disorganized mass, which made it difficult to get current out of the cell because the electrons would sometimes re-attach to their polymer donor. But, as the UCLA team state, their new polymer is more precisely arranged, which leads to some spectacularly different results:

"The UCLA technology arranges the elements more neatly -- like small bundles of uncooked spaghetti with precisely placed meatballs (see image below)," say the researchers. "Some fullerene meatballs are designed to sit inside the spaghetti bundles, but others are forced to stay on the outside. The fullerenes inside the structure take electrons from the polymers and toss them to the outside fullerene, which can effectively keep the electrons away from the polymer for weeks."

(Credit: UCLA)

The researchers are already working on how to incorporate the newly-discovered technology into actual solar cells. Yves Rubin, senior co-author of the study is excited for this next step, "When we can put them together and make a closed circuit, then we will really be somewhere."


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