Researchers have made significant strides in solar cell technology by developing a large-area triple-junction perovskite solar cell that has achieved a record power conversion efficiency (PCE) of 23.3%. This advancement, detailed in a recent publication in Nature Nanotechnology, could pave the way for more efficient and stable solar technologies aimed at reducing global carbon emissions.
The drive to enhance solar cell efficiency is critical for achieving net-zero emissions worldwide. Among various types of solar cells, multi-junction solar cells are anticipated to deliver some of the highest performance levels. These cells consist of a vertical arrangement of semiconductor layers, each designed to capture different segments of the solar spectrum, thereby optimizing energy conversion from sunlight to electricity. Theoretically, triple-junction solar cells can reach efficiencies as high as 51%, yet practical implementations often fall short due to challenges in material selection, manufacturing complexity, and costs.
In this collaborative effort involving researchers from Australia, China, Germany, and Slovenia, the team focused on creating a practical large-area triple-junction perovskite-perovskite-silicon tandem solar cell. Lead author Anita Ho-Baillie from the University of Sydney explained, “I am interested in triple-junction cells because of the larger headroom for efficiency gains.” Perovskite materials are particularly promising in the solar industry due to their cost-effectiveness and ease of fabrication, especially when combined with silicon.
The researchers implemented innovative design strategies to enhance cell performance and stability. They tackled surface defects present in the top perovskite layer by substituting conventional lithium fluoride with piperazine-1,4-diium chloride (PDCl). Additionally, the team replaced methylammonium, a commonly used component in perovskite solar cells, with rubidium, which significantly improved light stability.
To facilitate connectivity between the two perovskite layers, gold nanoparticles were utilized on a tin oxide substrate. These nanoparticles were carefully engineered to optimize electric charge flow and light absorption. Ho-Baillie noted the importance of visualizing the gold nanoparticles using transmission electron microscopy, which highlighted the critical transition point at which they become a semi-continuous film that could hinder the performance of the multi-junction cell due to unwanted absorption.
The culmination of these design innovations led to the creation of a 16 square centimeter triple-junction cell with an independently verified steady-state PCE of 23.3%, marking the highest efficiency recorded for a large-area cell. While smaller all-perovskite triple-junction cells have achieved even higher efficiencies, these were limited to one square centimeter in size. The study also produced a one square centimeter cell with a PCE of 27.06%, close to the highest performance levels noted, but the large-area cell”s achievements stand out.
Moreover, the one square centimeter cell underwent rigorous testing, passing the International Electrotechnical Commission”s (IEC) 61215 thermal cycling test, which involves subjecting the cell to extreme temperature variations. Remarkably, it maintained 95% of its initial efficiency after over 400 hours of continuous operation. This combination of high efficiency and successful thermal resilience suggests a promising future for the triple-junction architecture in practical applications, despite still being distant from theoretical efficiency limits.
