Generales

By: Jennifer Restrepo de la Pava-Journalist

With a methodology that shows in real time the performance of perovskite solar cells, their degradation mechanism and how it can be corrected, scientists from Universidad de Antioquia and Universitat Jaume I, in Spain, take another step forward in the global race for technological development, commercial application and massification of this synthetic mineral that promises to diversify and revolutionize solar energy technology. 

Solar panels with perovskite cells located on the terrace of the University Research Center (SIU). Photo courtesy: Esteban Velilla. 

Perovskite seems to be the "child prodigy" of solar cell materials. Only eight years of scientific exploration of this synthetic mineral for photovoltaic energy —obtained from solar radiation— have been enough for perovskite to equal silicon in energy efficiency (25%). Silicon is currently used for the manufacture of cells and has been in development for at least 50 years.

Perovskite was discovered in 1839, but it was not until 2009 that its properties for absorbing light and producing solar energy were detected. Both natural and synthetic perovskites —mixed with other materials and chemicals for enhancement— have a variety of electrical properties. They are insulators —non-conductors— semiconductors and superionic conductors.

Due to the combination of properties, including ion migration —an electrical current is transported through substances— and the low dependence of performance on temperature, this photovoltaic technology requires fewer processes for its manufacture, which makes it more affordable and allows it to be printed in large formats. Construction, fabrics, plastics, flexible substrates, among others, are applications that this material is suitable for. 

Despite the many advantages of perovskite, its stability is short, and it degrades in a short time. While the lifetime of a perovskite cell is 416 days, a silicon cell can last up to 20 years. This is where the challenge for scientists lies. They need to understand how perovskite degrades to solve this problem, improve the mineral’s long-term stability and turn it into a competitive technology.

Franklin Jaramillo Isaza, coordinator of Universidad de Antioquia’s Center for Research, Innovation and Development of Materials (CIDEMAT), and director of the research carried out in Colombia on this material, explained that the degradation of the cell can occur due to different factors. Light, water and oxygen contribute to this process.

To understand the phenomena that occur in solar cells, Esteban Velilla Hernández, a PhD student in materials engineering at Universidad de Antioquia; Franklin Jaramillo, who holds a PhD in chemistry; and Professor Ivan Mora Seró, from Universitat Jaume I’s Institute of Advanced Materials, in Spain, developed a methodology for analyzing perovskite cells that allows them to monitor their performance in real time and identify degradation mechanisms. 

According to Jaramillo Isaza, this methodology is based on the evaluation of the ideality factor, which shows how ideally a device behaves from an electrical point of view to monitor it in the open air. They correlated it with another parameter called “T80”, used to measure technologies that work outdoors. T80 is the time it takes for a device in real operating conditions to go down to 80% of its operation, the industrial reference time used to determine whether it is good or bad.

“The ideality factor, which is what we found as a factor to establish the real-time performance of the technology, will allow us to understand what is happening inside the device, the phenomena and degradation mechanisms of the cell. T80 shows the degradation period of the device", explained Franklin Jaramillo, PhD in chemistry.

Thanks to Universidad de Antioquia’s Solar Cells Laboratory, located at the University Research Center, the tests that were initially planned for laboratories were carried out on mini solar modules exposed to the elements day and night.

"Something very significant is that all the analyses and results took place outdoors. With this methodology, we are not only looking at the performance of these devices, but we are also relating them to degradation factors that were reported in the scientific literature and had not taken place until now. That was another of the great contributions: seeing what was happening with the device in real time", said Esteban Velilla, whose doctoral internship at the Spanish university prompted the research project.

This method proposed by the researchers provides a new understanding of degradation processes in outdoor cells, which is fundamental for the commercial application of perovskite solar panels. It also provides information for better data interpretation and understanding. 

According to researcher Franklin Jaramillo, this is the first time in the scientific field that this analysis methodology has been explored to predict real-time and future behavior of this or any other photovoltaic technology. 

Synthetic perovskite in different compositions. Solar Cells Laboratory, Universidad de Antioquia. Photo: Juan Pablo Hernández Sánchez.

Benefits of Perovskite

This synthetic mineral offers the possibility of broadening the spectrum of its applications by, for example, modifying its composition. "The fact that the composition of the material can be modified is a great advantage. You can change where the material absorbs light, which means changing its color. We can get red, orange or yellow solar cells. This results in a greater architectural integration. Silicon is black or bluish, and its color can’t be changed", added Professor Jaramillo Isaza.

Moreover, it offers a semi-transparent architectural integration. It can be installed as film on windows, through which you could partially see. Thus, the windows are converted into solar cells. The flexibility of the material is another advantage. It can be printed by rolls, even kilometers of it, or using different techniques, which contributes to massifying the technology and lowering production costs.

"It does not require ultra-high vacuum or high temperatures in its processing, unlike silicon. It is manufactured at room temperature, which represents a significant cost reduction. If we have those advantages, imagine what the price would be compared to silicon, whose cost for industrial production has dropped about 80% in the last 10 years. This is very important from the point of view of applying the technology on a massive scale", said Franklin Jaramillo. 

State of the Technology in the World  

The researchers explain that their perovskite solar cells are at technology readiness level 5. The goal is to reach 7 in the next few years.

"It's very close to eventually being commercialized in the world. There are spin-offs created to take this one step further. We want to think of a knowledge transfer strategy through the development of materials and technology because it’s probably difficult to create a manufacturing company in Colombia", reiterated Jaramillo Isaza.

The scientist added that some development with perovskite could be seen in the market in about three to five years; perhaps something small or preliminary that represents an important step in commercialization strategies.

The researchers emphasized that this breakthrough was possible thanks to the scientific literature on the subject and other research carried out by academic peers that served as a reference, in addition to the collaborative work with Universitat Jaume I.  

Global Contribution 

"This is the eye of the storm in the development of photovoltaic technology. Perovskite is an emerging material, and many people in the scientific community are working on this, so the contribution of the article in the journal is very favorable. The acceptance of the article in a journal of that stature is also a recognition of the capabilities that have been developed", said Professor Jaramillo. 

Given the importance of these findings, Nature Energy, which is one of the leading scientific journals and has the highest impact factor in the world, accepted in its January 2021 issue the publication of the research project High throughput analysis of the ideality factor to evaluate the outdoor performance of perovskite solar minimodules. 

Members of UdeA’s university community can find this research on the institution's databases. Those interested can also access the abstract of the article.