Scientists from the U.S. Department of Energy’s Ames Laboratory, led by Javier Vela, have advanced in the synthesis of low-dimensional nanomaterials. The team believes the development of these materials will improve computer processors, TV displays, and solar cells. These nanoparticles are one billionth of meter nanocrystals.

"We're trying to find out what happens with materials when we go to lower particle sizes, will the materials be enhanced or negatively impacted, or will we find properties that weren't expected," Vela said. "Our goal is to broaden the science of low-dimensional nanomaterials."

Some of the inorganic semiconductors under study by Vela and coworkers. (Ames Laboratory)Some of the inorganic semiconductors under study by Vela and coworkers. (Ames Laboratory)

One of the major advancements the scientists made was in the synthesis of germanium-based core-shell nanocrystals. The industry wants to use these technologies in solar cells, which would be a huge advancement for green energy.

The small particle size of the nanocrystals effects many things. Like transport properties, which is how well a nanocrystal conducts heat and electricity, or optical properties, how strong the nanocrystal interacts with light, absorbs light and emits light.

"Let's say you're using a semiconductor material to make a solar device, there's often different performance when solar cells are made from bulk materials as opposed to when they are made with nanomaterials. Nanomaterials interact with light differently; they absorb it better. That's one way you can manipulate devices and fine tune their performance or power conversion efficiency," said Vela.

There is a lot of interest in the industry in using the nanocrystals in quantum dot television and computer displays and other electronics that use LEDs.

"Ultimately the size of the nanocrystals being used can make a huge difference in the cleanliness or crispness of colors in TV and computer displays," said Vela. "Television and computer technology are a multibillion-dollar business worldwide, so you can see the potential value our understanding of properties of nanocrystals could bring to these technologies."

This research also made big advancements in the study of the synthesis and spectroscopic characterization of organolead halide perovskites, which are some of the most promising semiconductors for solar cells. They are low cost and easy to process. Vela says that photovoltaics are made of these materials can reach power conversion efficiencies of more than 22 percent. Vela and his team have focused their energy on mixed-halide perovskites. They found that these materials show interesting chemical photo physical property not realized before. They want to understand the correlation between the structure and chemical composition of these materials and their behavior in solar cells.

The group is also studying how to replace led in organolead halide perovskites. They ultimately want to use a material that is less toxic. Germanium seems to be a viable option. "In principle, this is an area that should be much better known, but it's not," said Vela. "When we've been able to substitute germanium for lead, we have been able to produce a lighter perovskite, which could positively impact the automotive industry, for example. This could have great implications for transportation applications where you don't want a lot of lead because it's so heavy.”

This research was published in the journal Chemistry of Materials.