Silver nanocubes for the development of solar cells

Researchers at Duke University have discovered that microscopic metal cubes may have great potential for absorbing light, a property that will lead to the development of more efficient and cheaper large-area absorbers for detectors or solar cells.

Researchers at Duke University have discovered that microscopic metal cubes may have great potential for absorbing light, a property that will lead to the development of more efficient and cheaper large-area absorbers for detectors or solar cells.

Metamaterials are man-made materials with properties not found in natural materials. They are constructed in such a way that leads to extraordinary control over waves, such as light rays. The production of these materials that are suitable for visible light is still a technological challenge that is normally achieved by the lithography method, in which metallic patterns are engraved in an inert material, similar to an ink-jet printer. Despite the effectiveness of this method in the production of such structures, the lithography method has a major limitation - it is very expensive and therefore very difficult to transfer it to the scale of extensive structures required for a variety of applications.

"Our new approach is more of a bottom-up type," said Cristian Ciracì, a scientist at Duke University's School of Engineering. "It may allow us to produce devices - such as efficient solar panels - that cover much larger buildings. During our experiments, we demonstrated an extremely simple method to achieve this goal." The research findings were published in the prestigious scientific journal Nature in December.

"For many applications or devices, the key factor is the material's ability to control the absorption of electromagnetic waves. Metals, for example, can have a high level of radiation reflection, a property that can be beneficial and useful for a number of applications, but for devices such as a solar cell, the required property is actually optimal and maximum absorption of light. At the same time, metamaterials based on metallic components are particularly effective as absorbing materials since both the electrical properties of the material and its magnetic properties can be controlled, depending on the design," explains the lead researcher.

The state-of-the-art metamaterial developed at Duke University consists of three main components - a thin layer of gold coated with a nanolayer of insulating material, on which is placed a layer of millions of nanocubes created in the process of self-aggregation. In the research experiments the nanocubes are of the metal silver. "The nanocubes are spread over the gold layer and in this way we are able to control the properties of the material by changing the geometry of the structure," explains the researcher. "In this way, we can now control the absorption capacity of large areas with a method that is beyond the capabilities of the lithography method."

Although metals, by themselves, tend to reflect light rays, the nanocubes act as tiny antennas that eliminate the metal's reflection of light from the surface. "By combining different components based on metamaterials into a common structure, it is possible to obtain a more complex spectrum of light reflection, while achieving a level of control required in more advanced applications, such as dynamic ink," explains the researcher.

The news about the study