Self-Assembling Nanomaterial Could Make Better Solar Cells

Researchers have designed new, self-assembling nanomaterials that show promise for the design of more efficient and affordable solar cells.

Though solar power has come a long way, solar energy-harvesting technology is still cost-prohibitive and largely inefficient compared to other ways to provide power, something researchers are diligently trying to change.

A team at the Advanced Science Research Center (ASRC) at The Graduate Center of The City University of New York (CUNY) has developed new, self-assembling nanomaterials that can help in this effort. The materials use a process called singlet fission to produce and extend the life of light-generated electrons, providing a potential pathway to more efficient and affordable solar-energy harvesting, researchers said in a CUNY news release.

In this illustration, DPP and rylene dye molecules come together to create a self-assembled superstructure in new materials developed by researchers at The City University of New York. Electrons within the structure absorb and become excited by light photons, and then couple with neighboring electrons to share energy and create additional excited electrons that can be harvested to create solar cells. (Image source: Advanced Science Research Center/The Graduate Center of The City University of New York)

Start With Industrial Dyes

Early research about the materials—developed by modifying some of the molecules in commonly used industrial dyes—suggests these materials could create more usable charges and increase the theoretical efficiency of solar cells up to 44 percent, said Andrew Levine, a Ph.D. student at The Graduate Center.

The resulting materials “facilitate a greater yield of harvestable electrons and extend the electrons’ excited-state lifetimes, giving us more time to collect them in a solar cell,” he explained in the news release.

The dyes researchers combined to create the new materials are two frequently used industrial dyes called diketopyrrolopyrrole (DPP) and rylene. This combination created six self-assembling superstructures, which scientists examined using electron microscopy and advanced spectroscopy.

In their investigation, researchers found that each combination had subtle differences in geometry that affected the dyes' excited states, the occurrence of singlet fission, and the yield and lifetime of harvestable electrons, they said.

Self-Assembly

Key to the design and behavior of the materials and is a self-assembly process, which causes the dye molecules to stack in a particular way, Levine said. This stacking allows dyes that have absorbed solar photons to couple and share energy with—known as “excite” in energy science terms—neighboring dyes. The electrons in these dyes then decouple so that they can be collected as harvestable solar energy, he said. Researchers described their work in a recent article the Journal of Physical Chemistry.

The research is significant for a couple of reasons. One is that it provides them with a library of nanomaterials that can be studied for harvesting solar energy, said Adam Braunschweig, lead researcher on the project and a professor in the ASRC Nanoscience Initiative and the Chemistry Departments at Hunter College and The Graduate Center. Researchers now can tune the material properties to increase their efficiency for solar-light harvesting, he said.

The materials' ability to self-assemble could also shorten the time for creating commercially viable solar cells, as well as provide a more affordable and less time-consuming fabrication method for these cells, researchers said.

The team plans to continue its work by developing a method of harvesting the solar charges created by their new nanomaterials, researchers said. This currently involves the design of a rylene molecule that can accept the electron from the DPP molecule after the singlet fission process. If their work is successful, these materials would both initiate the singlet fission process and facilitate charge-transfer into a solar cell, researchers added.

Elizabeth Montalbano is a freelance writer who has written about technology and culture for 20 years. She has lived and worked as a professional journalist in Phoenix, San Francisco and New York City. In her free time she enjoys surfing, traveling, music, yoga and cooking. She currently resides in a village on the southwest coast of Portugal.

 

 

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