A new interface control technology has been developed that can simultaneously enhance the efficiency and stability of perovskite-organic tandem solar cells. This next-generation solar energy technology can be applied not only to solar cells but also to photoelectrode devices that produce hydrogen using solar energy.
A research team led by Professors Kim Jin-young, Kim Dong-seok of the Graduate School of Carbon Neutrality, and Professor Shin Seung-jae of the Department of Energy and Chemical Engineering at Ulsan National Institute of Science and Technology (UNIST) announced on the 17th that they developed a technology to improve the performance and lifespan of perovskite-organic tandem solar cells by controlling the chemical state of Self-Assembled Monolayers (SAM).
Perovskite-organic tandem solar cells are next-generation solar cells that convert sunlight into electricity more efficiently by stacking two types of solar cells that absorb different wavelengths of light. However, if the interface between the transparent electrode and the perovskite layer is unstable in a tandem structure, charge transfer is hindered and long-term stability deteriorates.
The research team proposed a method to control the chemical state of 2PACz, a self-assembling material formed at this interface. By using potassium carbonate (K2CO3) to induce partial removal of hydrogen ions from the phosphonic acid group of the 2PACz molecule (deprotonation), the molecule becomes negatively charged and binds more strongly to the ITO transparent electrode. The deprotonated 2PACz (2PACz-K) formed in this process attaches more stably to the electrode surface, forming a uniform interface without being washed away by solvents during solar cell fabrication.
Perovskite solar cells applying this technology showed higher voltage and improved charge transfer characteristics. The perovskite-organic tandem solar cell produced based on this technology recorded a maximum power conversion efficiency of 25.1% and a high open-circuit voltage of 2.23V. It also demonstrated stability, maintaining more than 80% of initial performance after 220 hours of continuous operation under maximum power point tracking (MPPT) conditions.
The research team also applied this interface technology to photoelectrode devices that produce hydrogen by splitting water using sunlight. The tandem photoelectrode with the developed technology exhibited high photovoltage capable of inducing water-splitting reactions without external voltage, achieving a maximum solar-to-hydrogen conversion efficiency of 7.7%.
Professor Kim Jin-young said, "Through a strategy of controlling the chemical state of the interface at the molecular level, we have dramatically improved the performance and stability of solar cells," adding, "This can be utilized in the development of next-generation energy systems integrating solar power generation and green hydrogen production."
Dr. Son Jung-geon, doctoral candidate Ku Ha-eun, and Dr. Lee Woo-jin participated in this research as first authors.
The research results were published on February 5th in Energy & Environmental Science, a prestigious journal in the energy chemistry field. The research was supported by the National Research Foundation of Korea (NRF) under the Ministry of Science and ICT.
AI-translated from Korean. Quotes from foreign sources are based on Korean-language reports and may not reflect exact original wording.
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