Nanotechnology fuels solar cell research
Image courtesy of DOE.
JB: This is Earth and Sky, on improving solar energy, with the ultimate goal of producing hydrogen fuel.
Jin Zhang: . . .the idea is, if we make a device. . . all we need to do is take the device outside, leave it in the sun, fill it with water, and we should be able to generate hydrogen from it . . .
DB: That’s Jin Zhang, professor of chemistry and biochemistry at the University of California, Santa Cruz. He said using hydrogen for fuel is a good idea since hydrogen is plentiful, and, when used as a fuel, would leave behind few damaging environmental byproducts.
JB: But it takes electricity to break down water, H2O, into hydrogen and oxygen. And currently most electricity comes from the burning of fossil fuels. Zhang and his colleagues are working to let solar energy become the source of the electricity that separates the hydrogen from water. They’re designing a new type of solar cell, using nanotechnology – the science of the very small.
DB: They’re trying to use nano–sized particles of titanium dioxide – the pigment in white paint. When made into tiny nano–sized crystals, titanium dioxide has the property of absorbing light and generating electricity.
DB: Zhang’s research is another step in the direction of utilizing hydrogen for fuel – which he calls “a holy grail” in science and technology. With thanks to the National Science Foundation, we’re Block and Byrd for Earth and Sky.
Jin Zhang of U.C. Santa Cruz’s Department of Chemistry and Biochemistry was awarded $535,000 in grants from the U.S. Department of Energy this year for his part in two research projects aimed at developing new technologies for the production and storage of hydrogen fuel using nanostructured materials. Earth & Sky’s Jorge Salazar asked Dr. Zhang about solar cells of the future made with nanotechnology.
Jin Zhang: To give you some rough numbers, the solar cells that people currently use, the commercial solar cells – can reach 30% quite easily.
A lot of people are doing photovoltaic, or solar cell research right now. But we would like to design materials that can potentially have better efficiency, or if the efficiency is not better, maybe cheaper, so the cost for commercial applications is not just efficiency – it’s also the cost. Let me give you an example. Silicon is relatively expensive – that’s why we don’t have solar cells on our roofs nowadays for most families – it’s still cheaper to use electricity from conventional sources.
An area that a lot of people are working on is the use of titanium dioxide, metal oxides that are nanoparticles and relatively cheap, when compared to silicon. Currently the best efficiency for solar cells is based on titanium dioxide (TIO2) nanoparticles. Titanium dioxide by itself is white, it’s a powder and it cannot absorb solar light. In this case we put either a polymer or a dye molecule on the surface of these nanoparticles so that they can absorb sunlight. These molecules absorb sunlight and then inject an electron into TIO2, completing a circuit where we can produce electricity. This is already being done. The efficiency is about 10%. It’s not as efficient as silicon, that’s true, and while right now it’s more expensive because it’s not in commercial production, but let’s just for the purpose of argument that if we can produce these cells at 1/10 the price of silicon cells, even if my efficiency is a factor of three lower it’s still 10% rather than 30% efficiency, but I gain in price, the price is lower by a factor of ten. That’s still commercially viable for producing such solar cells. We’re not really striving to achieve the best efficiency, but we’re hoping to produce cells that have the best combination of efficiency and cost. These are two factors that we need to consider together, and also, making them environmentally friendly. To produce silicon, it requires a lot of chemical processes that use energy, chemicals, and byproducts. TIO2, which you might have seen in some of the paint materials that you use, is nontoxic and very abundant. It’s pretty cheap.
Our thanks to:
Jin Zhang
Professor of Chemistry
Zhang Research Group
Department of Chemistry
University of California
Santa Cruz, CA
