Self-Assembling Molecules Enhance Both Efficiency and Stability of Perovskite Batteries!

Joint Research Team Led by Professor Kim Bongsoo at UNIST Develops High-Performance Self-Assembled Hole Transport Layer
13% Improvement in Cell Efficiency and Outstanding Light Stability
Published in Angewandte Chemie

A research team has achieved both high efficiency and stability in next-generation perovskite solar cells by developing molecules that self-assemble on substrates.

A joint research team led by Professor Kim Bongsoo from the Department of Chemistry at UNIST, Professors Kim Dongseok and Kim Jinyoung from the Carbon Neutral Graduate School, and Professor Lee Kyunggu from the National University of Gunsan has developed a new self-assembling hole transport layer material that enhances both the efficiency and stability of perovskite solar cells.

Research team. (From the bottom left, counterclockwise) Professor Dongseok Kim, Professor Bongsu Kim, Dr. Shahid Amin (first author), Researcher Youngwan Lee, Researcher Junggun Son (first author), Researcher Dongmin Lee (first author). Provided by UNIST

Perovskite solar cells are next-generation solar cells with excellent price competitiveness due to their low-cost materials and manufacturing processes.

The self-assembled monolayer (SAM) used in these cells is a material that transfers holes (positively charged particles) generated in the light-active perovskite layer to the electrode. The SAM hole transport layer is formed by molecules that self-assemble on the substrate, which allows for even lower processing costs compared to polymer-based hole transport layers.

The research team developed MeS-4PACz, a molecule with a structure designed to further enhance hole transport performance compared to the previously used 4PACz molecule for forming SAMs. Perovskite solar cells using this new material achieved a photoelectric conversion efficiency of 25.16%, an improvement of over 13% compared to conventional SAMs.

Solar cells generate electrical energy through the movement of photogenerated electrons (negatively charged particles) and holes to the electrodes, so efficient transport of both to the electrodes increases cell efficiency. In addition, the hysteresis value, an indicator of solar cell output and long-term stability, was significantly improved.

Light stability was also enhanced, with the new cells maintaining 93% of their initial efficiency after 500 hours of exposure to intense sunlight, showing almost no degradation. In contrast, cells using 4PACz saw their efficiency decrease by more than 20% after 500 hours.

The developed MeS-4PACz is a form of 4PACz with a methylthiol functional group (-SCH₃) added, which aligns well with the energy level of the perovskite layer, allowing holes generated in the perovskite layer to move smoothly to the electrode.

Furthermore, the sulfur in the methylthiol group forms strong chemical bonds with the cations in the perovskite, helping to maintain the perovskite layer in its initially optimized state even under solar exposure and greatly enhancing interfacial stability.

Research Illustration. (Analysis Results of the Developed Self-Assembled Charge Transport Layer Characteristics)

Professor Kim Bongsoo explained, "The developed SAM is a material that maximizes the low processing cost advantage of perovskite solar cells while simultaneously achieving stability and efficiency, greatly increasing the market entry potential of perovskite solar cells."

This research was led by Dr. Shahid Ameen and researchers Lee Dongmin and Son Junggeon from UNIST, as well as researcher Abdullah Bin Faheem from Gunsan National University, as first authors.

The results have been published in the prestigious chemistry journal Angewandte Chemie International Edition and are awaiting official publication.

The research was supported by the National Research Foundation of Korea under the Ministry of Science and ICT.

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