Science & Technology, Canada (Commonwealth Union) – A group of researchers from the University of Toronto’s Faculty of Applied Science & Engineering has achieved a significant breakthrough in the field of perovskite solar cells. This international team has successfully developed a perovskite solar cell that demonstrates remarkable resilience against high temperatures, lasting for more than 1,500 hours. This achievement marks a crucial milestone as it brings this emerging solar technology one step closer to practical commercial implementation.
The team’s groundbreaking work appeared in the prestigious journal Science.
According to Ted Sargent, a professor associated with both the Edward S. Rogers Sr. department of electrical and computer engineering at the University of Toronto and the departments of chemistry and electrical and computer engineering at Northwestern University, perovskite solar cells hold the potential to address the efficiency limitations faced by the current industrial standard, which relies on silicon-based technology. This novel technology presents promising pathways to overcome these limitations and revolutionize the solar energy industry.
He further indicated that as a result of its multi-decade head start, silicon remains preferential in certain areas, that consist of stability. This research indicates the way the gap can be sealed.
Conventional solar cells rely on high-purity silicon wafers, which are energy-intensive to manufacture and have limited absorption capabilities across the solar spectrum.
In contrast, perovskite solar cells utilize nanoscale crystal layers, making them more suitable for cost-effective production methods. By adjusting the size and composition of these crystals, scientists can customize the wavelengths of light they can absorb.
Moreover, it is feasible to stack multiple perovskite layers on top of each other or combine them with silicon solar cells, expanding their ability to capture a broader range of the solar spectrum and enhance overall efficiency.
Recent advancements, including those from Sargent’s research lab and other institutions, have brought perovskite solar cell efficiency within a comparable range to silicon cells. However, the issue of stability has received less emphasis in these developments.
According to So Min Park, a postdoctoral fellow in Sargent’s lab and one of the three co-lead authors of the study, the reason we aimed to work at high temperatures and high relative humidity was to gain a deeper understanding of which components could potentially fail first. This knowledge would then help us devise effective strategies to enhance these components and improve overall performance.
“We combined our expertise in materials discovery, spectroscopy and device fabrication to design and characterize a new surface coating for the surface of the perovskites. Our data showed that it is this coating, made with fluorinated ammonium ligands, that enhances the stability of the overall cell.”
Perovskite solar cells typically feature a passivation layer, encompassing the light-absorbing perovskite layer and facilitating the movement of electrons into the surrounding circuit.
However, depending on its composition and exposure to heat and humidity, the passivation layer can undergo deformations that hinder the electron flow.
According to Mingyang Wei, a PhD graduate from the department of electrical and computer engineering, currently a postdoctoral fellow at École Polytechnique Fédérale de Lausanne and co-lead author of the study, many research groups use passivation layers containing bulky ammonium ions, which are nitrogen-containing organic molecules.
“Even though they form stable 2D structures at room temperature, these passivation layers can degrade at elevated temperatures, due to their intermixing with underlying perovskites. What we did was replace typical ammonium ions with 3,4,5-trifluoroanilinium. This new passivation layer does not intercalate into the structure of the perovskite crystals, making it thermally stable.”
Subsequently, the team conducted thorough performance tests on the cells, employing continuous measurements under specific conditions. These conditions included subjecting the cells to a temperature of 85 degrees Celsius, a relative humidity of 50 per cent, maximum power-point tracking, and illuminating them with an intensity equivalent to full sunlight. In their research paper, they disclosed a crucial finding known as T85, which signifies the duration it takes for the cell’s performance to decline to 85 per cent of its initial value. Remarkably, the reported T85 value was an impressive 1,560 hours, highlighting the remarkable stability and endurance of the perovskite solar cell under such challenging conditions.
