A research group from the Netherlands’ Eindhoven University of Technology, energy research institute Differ, the University of Twente, and China’s Peking University is seeking to use fluoride to reduce instability and degradation in perovskite solar cells.
In a paper published in Nature Energy the scientists claim to have developed a perovskite-based solar cell with a power conversion efficiency of 21.46% that is said to maintain 90% of its efficiency after 1,000 hours under extreme light and heat conditions.
The longevity was obtained, according to the researchers, by adding sodium fluoride to the perovskite layer during the manufacturing process. “With the help of first-principles density functional theory calculations, we argue that the fluoride ions suppress the formation of halide anion and organic cation vacancies, through a unique strengthening of the chemical bonds with the surrounding lead and organic cations,” they explained in the study.
The scientists said fluoride works on a perovskite cell in a similar manner to its behavior in toothpastes, with fluoride ions forming a protective layer around the crystal, preventing the diffusion of harmful defects.
Still no nearer commercialization
The small size and high electronegativity of fluoride ions was identified as the main reason for their effectiveness in improving the stability of perovskite cells, compared to other halogens.
The scientists said another five to ten years may be needed for perovskite cells to reach commercial production. “We still don’t have all the answers to why some materials are more effective than others in increasing the long-term stability of these cells”, said research coordinator Shuxia Tao, from the Center for Computational Energy Research.
Similar research has recently been conducted by, among others, the University of California San Diego, UCLA and Chinese module manufacturer Solargiga, as well as the Netherlands’ University of Groningen and another Peking University team.
Despite the proliferation of promising research projects, the stability, durability and cost of perovskite solar cells remains problematic for the technical feasibility of commercialization.