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New LY-m self-assembled monolayer boosts perovskite solar efficiency and thermal stability
A solar cell material that operates normally even under extreme temperature changes ranging from −100°C to 100°C has been developed. It is expected to contribute to the commercialization of solar cells in extreme environments.
The National Research Foundation of Korea announced on the 3rd that a joint research team led by Professors Yang Chang-Duk and Shin Seung-jae of the Department of Energy and Chemical Engineering at Ulsan National Institute of Science and Technology (UNIST), and Professor Song Myung-Hoon of the Department of Materials Science and Engineering, has developed an interfacial material named ‘LY-m’ that forms a dense and stable arrangement on electrodes by controlling the molecular connection position of a self-assembled monolayer (SAM).
A self-assembled monolayer is an ultrathin film with a thickness of a single molecular layer, formed as specific molecules spontaneously bind and align on a substrate surface. It is a material that reduces defects in perovskite solar cells and maximizes charge transport.
In next-generation photovoltaic technology using perovskite solar cells, an inverted architecture, in which the top and bottom structure of the charge-transporting layers is flipped, is attracting attention as a way to maximize efficiency and stability. When placing the perovskite (i) layer in the middle and stacking a hole transport layer (p), which transports positive charges, and an electron transport layer (n), which transports negative charges, the n-i-p configuration is called the regular structure, while the p-i-n configuration is called the inverted structure.
In inverted devices, the interface between the transparent electrode (ITO) and the perovskite absorber layer is a critical region that determines solar cell performance. Although self-assembled monolayers are widely used as a hole transport layer within this interface, they have limitations in that, if the molecules are not uniformly arranged or are exposed to heat, the solar cell can suffer from large energy losses and reduced long-term stability.
The research team synthesized three isomers by maintaining the basic structure of the self-assembled monolayer molecules while changing only the position of the connecting linker in the middle. Isomers are substances that share the same chemical formula but have different internal molecular structures or arrangements, resulting in different physical and chemical properties.
The team synthesized LY-o, LY-m, and LY-p by varying only the connection position of the self-assembled monolayer molecules to ortho, meta, and para (bonding positions on a benzene ring), respectively. When each isomer was applied to the perovskite interface, the LY-m molecule with a meta-position connection exhibited the most outstanding properties.
The LY-m molecules formed a dense and uniform film in a tilted configuration on the transparent electrode substrate, showing the highest binding energy among the three isomers while also tending to minimize defects.
When actually applied to inverted perovskite solar cell devices, LY-m achieved an ultrahigh power conversion efficiency of 26.39%.
In an extreme thermal cycling test in which the temperature was repeatedly switched between −100°C and 100°C, each for 30 minutes, devices using conventional commercial materials stopped operating, whereas devices using LY-m maintained more than 91% of their initial efficiency and continued to operate normally.
Professor Yang said, “The performance of a solar cell is greatly influenced not only by the light-absorbing material but also by how perfectly each interface between layers is formed,” adding, “This study demonstrates that efficiency and stability can be simultaneously enhanced through precise molecular-level design, and it increases the prospects for applying solar cells in environments such as space and aviation, where extreme temperature fluctuations are expected.” The research findings were published online on the 3rd of last month in the international journal Joule.
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doi.org/10.1016/j.joule.2026.102600
