Michael Grätzel , a scientist at the Federal Polytechnic School of Lausanne, Switzerland, and Paul Alivisatos , a researcher at the University of California in Berkeley, USA, received this Wednesday the thirteenth edition of the BBVA Frontiers of Knowledge award in the Basic Sciences category for achieving "Fundamental discoveries that have allowed the use of nanostructures for energy conversion," according to the jury's minutes.
The findings of the two scientists are "fundamental" for the development of new nanomaterials that are being applied in the production of energy renewable energies and the latest generation electronics. "Grätzel's groundbreaking work includes the invention of a type of dye-sensitized cell that mimics the photosynthesis process and improves solar power generation," says the jury. Alivisatos, for its part, has used nanocrystals to emit light and control color very precisely. Their work, in addition to creating screens for QLED televisions, has helped maximize the absorption and use of solar panels.
According to the jury, the two scientists are “pioneers in controlling the light-matter pair, through the use of nanomaterials ”. After receiving the award, Alivisatos stated by videoconference: “Michael Grätzel has investigated how to convert the light that enters the system into electricity, while the applications derived from my work have more to do with how to convert the energy into light that comes out. the system, and that people can use. ”
The two winners are convinced that, faced with the threat of climate change and the need to produce renewable energy on a large scale, the new lines of research opened by their work represent one of the possible solutions from science and technology. “Climate change,” says Grätzel, “is our main challenge. We must reduce the use of fossil fuels and photovoltaic energy has to increase its capacity 200 times in the coming decades. ”
Alivisatos agrees and recognizes that part of that challenge is learning to manufacture new materials that can capture the sun's energy, with the lowest possible losses. “We have found that nanomaterials can be manufactured with very high quality and at relatively low cost. They can be used to absorb sunlight, and by doing so they do not lose energy in the form of heat, which allows a more efficient conversion into electricity. ”
The cell that mimics photosynthesis
Michael Grätzel was the first to combine molecular systems and nanoparticles to make a new type of solar cells that mimic photosynthesis. Their discovery aims to turn sunlight into a clean, efficient and cheap source of electricity on a large scale
Photosynthesis, the natural process through which plant leaves convert sunlight into energy for growth , served as inspiration for Grätzel. According to the scientist, who was born in Dorfchemnitz, Germany, in 1944, the new solar cells that bear his name use a pigment similar to that of tree leaves, absorb sunlight and generate electrons. To produce energy, these electrons are collected and transported by a semiconductor material, in this case titanium dioxide.
The two winners are convinced that, given the threat of climate change and the need to produce renewable energy on a large scale, the new lines of research opened by their work represent one of the possible solutions from science and technology
According to the jury, the great contribution of Grätzel was to use the titanium dioxide in nanoparticles, and not in conventional silicon cell plates. Each nanoparticle of titanium dioxide is coated with the pigment, and the result is a fluid from which solar cells are made. "It was the first time that nanoparticles were used to build photovoltaic cells, nobody had thought about it before," Grätzel explained by videoconference after learning of the failure. "The first time we tried it it was exciting, it surprised us because we achieved a conversion of light into energy thousands of times higher than we expected."
Grätzel, who graduated in Chemistry in 1968 from the Free University of Berlin and received his doctorate in Physical Chemistry in 1971 from the Technical University of Berlin, presented his new photovoltaic solar cell in 1991 in a publication in Nature , which has been cited by dozens of thousands of times and that has given rise to dye-sensitized solar cells, also known simply by the name of their inventor: Grätzel cells.
This development has generated "thousands of patents" and "has opened a whole new field of research ”, Assures the researcher. The advantages of these cells, according to Grätzel, are multiple: abundant raw materials, a cheap manufacturing process, transparency –which allows them to be placed in windows–, flexibility and the ability to obtain electricity also from ambient light, such as that found in a room.
Nanocrystals for high resolution displays
Alivisatos nanocrystals, also called quantum dots, have hundreds of applications, from the search for new sources of clean energy to consumer electronics and biomedical imaging techniques. According to the researcher, who was born in Chicago, United States, in 1959, “an electron in a nanocrystal can emit light, and the color of that light will depend on the size of the nanocrystal. If it is small, the energy of the light will be higher, so it will be a more blue light. In this way, nanocrystals can be used to make materials that emit all the colors of nature. ”
One of its most successful applications of Alivisatos nanocrystals is the monitors developed in the mid-90s and which are now incorporated into televisions QLED. Alivisatos proved that it was possible to manufacture them with high resolution and make them very efficient in the use of energy. “On a color screen”, points out the winner, “there is always a red, blue and green that interact within our eye to reproduce all the colors around us.”
In addition, in the field of biomedicine, Alivisatos and its The group developed nanocrystals for staining of biological samples – by adjusting the size of the nanocrystal, the fluid can label one type of cell or another. Currently there are hundreds of products based on quantum dots for biomedical imaging on the market.
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