In her PhD, the Brazilian scientist Natasha Gruginskie studied how to make solar panels produce more electricity and last longer.
“Throughout high school, I had no idea what I wanted to do.” Those who look at Natasha Gruginskie’s successful career wouldn’t imagine that she, like many of us, also had many doubts about a future profession while she was a teenager. The native of Porto Alegre, Brazil, was encouraged by her father to study and be curious about the world since she was a child. So, from an early age, she was already considering going into academia. She just didn’t know which field. “I thought about studying many different degrees: architecture, chemistry, nutrition.” But it was her aptitude and inclination for the maths and technology area that made her choose Energy Engineering.
During her undergraduate studies, she fell in love with research and innovation introduced in some disciplines. By the end of college, she couldn’t see herself doing anything else but being a scientist. So after graduation, the decision to do a Master’s came naturally. She then opted for a master’s degree in Materials Engineering in her hometown. And for her Ph.D., she decided to apply this knowledge to another area of interest: renewable energies.
Renewable energies are those that come from unlimited natural sources, that is, that are constantly replenished. These include sun, rain, wind, and tides. In her Ph.D., Natasha focused on improving a device that captures solar energy and converts it into electrical energy, the so-called solar panels. Although they already exist on the market, these panels aren’t entirely efficient in generating electrical energy. Moreover, their efficiency in generating energy diminishes over time, and they can be very expensive to produce.
So in her Ph.D. in Applied Materials Science at Radboud University in Nijmegen, Netherlands, Natasha studied how to make solar panels produce more electricity. These panels are composed of units called solar cells. In their study, Natasha and her colleagues made several changes to these cells to test whether they could become more efficient. “By changing the structure of these cells a little bit, they generate different amounts of energy. By analyzing this relationship, we tried to find out which configuration was the most efficient,” explains Natasha.
Solar cells are made of a semiconductor material that is capable of absorbing energy from sunlight. Let’s think of sunlight as a ray made up of tiny particles, the photons. We can think of solar cells, on the other hand, as a network made of the same material. The chemical bonds between these materials are what keep the net connected. When one of these photons collides with the net with sufficient energy, it can displace an electron from the chemical bond in the net. It is like when one marble hits another, when the ball that was hit occupies approximately the position of the ball that was displaced. But then what happens to the electron that is displaced, where does it end up? Due to the structure of the solar cell, which also has an electric field, this displaced electron is attracted to a metal part of the cell. Since metal is a conductive material, that is, it can conduct energy, this electron, and many others that were displaced, are now transported to an electric circuit through the metal, generating electric current.
The semiconductor material present in solar cells can be made up of different chemical elements. The most common, used in residential solar panels, is silicon. This material, highly abundant on Earth, is relatively cheap, and is, therefore, most commonly used in everyday applications. However, this type of material isn’t energy-efficient. Another material, more expensive but also more efficient than silicon, is gallium arsenide (GaAs). Such material is mainly used in space applications, such as satellites and probes. “These satellites are very important for our communication to transmit radio waves, GPS signal, and even internet,” explains Natasha. In addition, it has been applied to cars, drones, and pseudo-satellites.
Even though it is more effective, the conversion of solar energy into electricity isn’t 100% with GaAs cells. “The record efficiency of GaAs solar cells is 29.1%. If the average power coming from the sun is 1000 Watt/square meters, a solar plate of 1 square meter would be the equivalent of a 291W generator. When we look at our electricity bill, we see consumption in “kWh”, that is, we can compare this generator power multiplied by the hours of sunlight, to know how much we would need to generate enough energy for our house. If we had 8 hours of sun on these panels, in one day we would have a generation of 2.3 kWh. For comparison, in my house we use about 3.5kWh a day,” explains Natasha.
Thus, to become more energy-efficient, studies aimed at improving these solar cells are essential. “Improving the power output of solar cells ensures that they are more reliable and resilient in applications. It also lowers the final cost and increases the autonomy of the technologies powered by them. As well as being a renewable energy source,” Natasha explains. In addition, “high-efficiency solar energy generation can also facilitate the development of other technologies, such as autonomous drones, solar cars, electronics that can be charged off-grid, among others” adds the scientist.
Therefore, in her Ph.D., Natasha studied how the design of solar cells composed of GaAs affects energy production and durability, especially in the space environment, where these cells are most commonly used. “I manufactured many solar cells, varying certain aspects of their design, and analyzed the results. I used theoretical models to try to understand the behavior of light and electrons inside the cells. In addition, I simulated the conditions of the space environment, such as high temperatures, proton and electron bombardment. And evaluated how this affected the life of these devices.”
One aspect of the solar cell design that was evaluated by Natasha was weight. As you can imagine, quite a lot of energy is required to get an object into space. In practical terms, that means a great deal of money. Therefore, the weight of the solar cells, and thus the solar panels, is a limiting factor. One way that can reduce both weight and cost is to introduce a mirror into the solar cell. This is used to concentrate the sun’s rays. This leads to a smaller area being needed, and, therefore, less weight and lower cost. Another way, of course, is simply to use a lighter material. In Natasha’s case, she used a type of material called thin films to produce the cells.
Applying these modifications, she and her colleagues evaluated how these experimental solar cells reacted to an environment simulating space, particularly regarding energy efficiency and durability. As a result of these analyses, Natasha and her colleagues have published several papers in which they evaluated different aspects of solar cells. Among these papers, in one published this year, the researchers investigated how the irradiation of protons coming from the “fictitious” space affected the performance of solar cells. Based on the results, the researchers were able to conclude that the use of thin films makes the solar cells also thinner. In practice, this leads them to be more resilient to radiation damage. In the other papers, they evaluated how electron irradiation and temperature affect these experimental solar cells. In addition, more technical aspects and changes in the cell design were also tested.
And these studies continue in full mode. Today Natasha is still working in the same laboratory, but now as a postdoc. When asked what motivates her to continue being a scientist, she doesn’t hesitate: “Progress. I believe that technology is the great force that is improving the quality of life of humankind, and I have the opportunity to contribute to this. Renewable energy and space exploration are, in my opinion, two research fronts that are driving science today. The fact that I am involved in these areas is inspiring to me.”
When she is not producing solar cells or analyzing her data, Natasha enjoys doing crafts, such as painting, doing bookbinding, and refurbishing small furniture. In addition, she enjoys running and exercising.
Thank you so much for telling us your story, Natasha! May you continue to contribute to scientific and technological advancement for a long time!
You can keep following Natasha’s career here.