As the world’s energy demands continue to increase, the efforts of scientists to find ways to capture, harness, store and convert various renewable energy sources such as wind, solar and hydro are of particular importance.

Among those renewable sources, solar energy, as Dr, Jean-Luc Bredas, Director of KAUST’s Solar and Photovoltaics Engineering Research Center (SPERC), recently stated through a Nature Middle East article, is likely the most sustainable one. But although the planet, particularly Saudi Arabia and the region, receives an abundant amount of sunlight, the methods of conversion of those sunrays into energy still have a lot of room to be optimized, as KAUST’s Prof. Aram Amassian also argues in another Nature article.

Materials science plays a major role in tackling the challenge of maximizing the capture and conversion of solar energy. KAUST’s Functional Nanomaterials Laboratory (FuNL) group, headed by its Principal Investigator, Prof. Osman Bakr, specializes in “the synthesis, characterization, and assembly of organic and organic-inorganic hybrid nanomaterials of novel optical, electronic and magnetic properties that will become the future building-blocks for solar cells, batteries, photonic and optoelectronic devices.”

In the area of photovoltaics, nanoparticles can absorb light in different wavelengths depending on their size. Nanoparticles are materials comprised of tens to hundreds of atoms. Their properties depend on the number of atoms they’re comprised of. “A big part of my group’s work is how to control the number of atoms on a nanoparticle and so ultimately to control their properties. That’s in a nutshell what we do,” said Prof. Bakr. “We have to be able to tune the nanoparticle size and composition so that it harvests as much of the sunlight as it can; so that we have as efficient solar cells as possible.”

Third Generation Solar Cells

Unlike first generation solar cells that are made of silicon, and usually require high temperatures to process, nanoparticles can be made into inks and then inkjet printed, or solution-processed, at very low temperatures. These absorbing materials, which can be coated on top of solar panels, are referred to as third generation solar cells.

One of the main advantages of being able to operate at a lower temperature is the potential integration with things like roll-to-roll printing as in a printing press. Possible applications include printing photovoltaic thin films onto a building’s glass windows as a substrate. Prof. Bakr adds it’s also possible to control the color of the individual nanoparticles. It’s therefore possible to regulate color of the paint or the ink.

This has important implications also for the growing field of flexible electronics. Because nanoparticles can be spray-coated, they can definitely be painted onto flexible substrates, or laminated onto various surfaces.

Nanoparticles for Catalysis

Nanoparticles have not only become important materials for photovoltaics (solar cells) but they’re also useful for catalysis. A lot of the catalysis industry relies on the use of precious metals. Understandably, there’s a particular concern with using as little of those precious metals as possible in the catalytic process -- while nonetheless maintaining efficiency. “That’s why we have to develop ways of controlling and making the nanoparticles as small as possible, with the right amount and kinds of shapes, so that they catalyze the reactions efficiently,” Prof. Bakr explains.

“The general idea behind catalysis is that certain reactions take a long time to happen, or they require very high temperatures to occur. So certain nanoparticles mediate chemical reactions. They allow them to occur faster or at a lower temperature or lower energy,” he adds.

Essentially, nanoparticles don’t participate in the reaction but they mediate it. They’re not a product in the reaction but they regulate the reaction itself. Materials usually grow in crystals; and these crystals have facets. Some facets are very active while other ones are not. The scientists from KAUST’s Functional Nanomaterials Laboratory (FuNL) are interested in controlling the nanoparticles so that they predominantly have facets that are active.

For instance, the KAUST Catalysis Center (KCC) is interested in optimizing fuel cell reactions by reducing oxygen levels. Also, one of the challenges with fuel cells is that there are materials in the cathode and nanode that are expensive precious metals. “So by making them into nanoparticles we can reduce the amount of precious materials while keeping the surface area very high; ensuring that we save a lot and make things like fuel cells applicable,” said Bakr.

Industrial Applications and Implications for Saudi Arabia

Prof. Osman Bakr’s group is currently working closely with a major industrial partner to develop light-harvesting nanoparticles – particularly relating to photocatalysis. Water splitting reactions, for instance, use photocatalysis to split hydrogen from water directly from sunlight.

“Photocatalysis works by converting for example water or organic solvents into hydrogen directly through sunlight. These nanoparticles catalyze this conversion. So we work closely with several groups in the KAUST Catalysis Center. We specialize in nanoparticles and they specialize in the catalytic part,” as Prof. Bakr outlines.

Considered a part of nanotechnology, nanoparticles represent a highly refined product or material. According to Prof. Bakr, “It has the potential to carry the Saudi chemical industries to go up the value chain. Instead of selling or producing commodity materials, Saudi Arabia can potentially develop a material category that is very specialized, requiring a lot of research to produce and, thus, not so easy to replicate.”

He argues that nanotechnology can potentially help propel emerging sectors of the Saudi economy and help create a startup culture that can eventually result in the development on chip manufacturing companies and so forth.

-By Meres J. Weche, KAUST News