Light conversion: super-powerful solar panels will help to explore distant planets

Russian researchers have discovered new physical mechanisms that significantly enhance the refractive indices of light in nanoparticles. This opens the way to the creation of fundamentally new devices in a wide variety of fields. In particular, the results can form the basis of fourth—generation solar panels with record efficiency, which will allow efficient operation even in remote areas of space from the Sun. In addition, the identified effects create the basis for the development of inexpensive flexible displays, new type of smart windows and high-precision medical sensors.

How optical defects improve the properties of materials

Scientists from Kazan Federal University (KFU) have developed a new way to control the properties of materials using artificial defects. The method can become the basis for breakthrough developments in the field of solar energy, miniature electronics, high-precision sensors and ultra-sensitive sensors.

It is based on the interaction of light with nanometer—scale structures such as quantum dots, nanocrystals, thin films, and other similar objects. Researchers have shown why, when a material is reduced to an ultra-small size at its edges and in places with a disrupted structure, light particles affect electrons in a special way.

— Traditionally, defects were considered as something undesirable that worsens their properties. However, in recent years, there have been more and more studies that show that violations of the internal structure of a material, if you learn how to control them, will help develop new—generation technologies," Professor Sergey Kharintsev, head of the Department of Optics and Nanophotonics at the Institute of Physics of KFU, told Izvestia.

He explained that microscopic objects, when exposed to light (for example, a laser beam), have more complex effects than in ordinary materials. Structures of limited size, as it were, give additional "shocks" to electrons, which allows them to interact with photons in a different way. This, in particular, increases the concentration of free charges in the conduction band and ensures an increase in the refractive index — that is, a change in the direction of light propagation.

— We have investigated this using the example of gold particles smaller than 5 nm. It turned out that their ability to refract light increases. Especially in resonance conditions (when the frequency of light coincides with the frequency of vibrations of electrons in a particle), this indicator can increase by 10 times or more. There is also an amplification in a wider range. In addition, there are other effects that together lead to an increase in the refractive index," said Elina Battalova, an engineer at the Department of Optics and Nanophotonics at the KFU Institute of Physics.

According to her, the high refractive index in nanomaterials opens the way to the creation of a number of promising products. For example, transparent electrodes. They can be used for displays in smart glasses or flexible smartphones, as well as in medical sensors that are attached to the skin. These developments will also help in creating windows that independently regulate the amount of light and heat entering the room.

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New generation solar panels

Another area where open effects may be in demand is the creation of a new generation of solar panels. Perhaps they will be able to overcome the Shockley–Quiser limit, the theoretically calculated maximum efficiency for converting light energy into electricity. For silicon solar panels, this figure is 32%, the specialist said.

According to the researchers, such panels, in particular, will expand the capabilities of spacecraft and will allow even small probes and satellites to be equipped with powerful scientific instruments. In addition, they will increase their service life and help to carry out long-term missions away from the Sun. For example, to distant planets.

— The described effects really open up new ways for the engineering of optics and photonics as tools that enhance the interaction between light and matter. Such technologies will increase the efficiency of solar panels by reducing the proportion of reflected light and parasitic absorption," Pavel Gostischev, a leading researcher at the Laboratory of Advanced Solar Energy at NUST MISIS, told Izvestia.

At the same time, in order to move to practical application, it is necessary to scale a well-reproducible technology for the synthesis of nanoparticles and defective structures that exhibit open effects. It is also necessary to develop a technology for their implementation directly into solar cells, the specialist added.

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Currently, scientists are exploring ways to increase the efficiency of solar panels, he noted. However, exceeding the Shockley–Quiser limit and creating a "fourth generation" of solar cells require not only an unusually high refractive index, but also careful consideration of optical losses, device stability, and large-scale manufacturing capabilities.

— KFU scientists have obtained results that can play an important role in future technologies. For example, opportunities are opening up for optical control of electrons in silicon transistors, the dimensions of which are approaching the subnanometer scale. This will be a new step in the development of computing technology. Open effects will also be in demand in devices for fast and accurate quality control of silicon wafers for microchips," Nikolai Kravchenko, Acting director of the Institute of Physical Research and Technology at the Rudn University, told Izvestia.

At the same time, in order to transfer scientific developments from the laboratory into real products, it is necessary to work out the commercial side of the issue — to understand who will become the consumer, find sources of financing for expensive research and establish contacts with industrial partners, he added.