A team led by Professor Sung-Yeon Jang from the School of Energy and Chemical Engineering at UNIST has developed the world’s most efficient quantum dot (QD) solar cell. The team used a novel ligand exchange technique to create organic cation-based perovskite quantum dots (PQDs), which have exceptional stability and fewer defects. The technology achieved an impressive 18.1% efficiency in QD solar cells, the highest recognized by the National Renewable Energy Laboratory (NREL) in the U.S. The research, co-authored by Dr. Javid Aqoma Khoiruddin and Sang-Hak Lee, was published in Nature Energy.
Quantum Dot Solar Cells: A Significant Leap in Solar Energy Efficiency
A recent study published in Nature Energy on January 27, 2024, has reported a significant advancement in solar energy technology. The research, led by Professor Sung-Yeon Jang from the School of Energy and Chemical Engineering at UNIST, has resulted in the development of highly efficient quantum dot (QD) solar cells. These cells have demonstrated exceptional performance and stability, even after long-term storage, marking a significant step towards the commercialization of next-generation solar cells.
The Promise of Perovskite Quantum Dots
Quantum dots (QDs) are semiconducting nanocrystals with dimensions ranging from several to tens of nanometers. Their photoelectric properties can be controlled based on their particle size, making them a promising material for solar cells. Perovskite quantum dots (PQDs), in particular, have attracted significant attention due to their superior photoelectric properties. The manufacturing process for PQDs is relatively simple, involving spraying or application to a solvent, which eliminates the need for a growth process on substrates. This streamlined approach allows for high-quality production in various manufacturing environments.
Overcoming Challenges with Organic PQDs
Despite the potential of PQDs, their practical use as solar cells requires a technology that reduces the distance between QDs through a process known as ligand exchange. This process binds a large molecule, such as a ligand receptor, to the surface of a QD. Organic PQDs, however, face significant challenges, including defects in their crystals and surfaces during the substitution process. As a result, inorganic PQDs, which have a limited efficiency of up to 16%, have been predominantly used as materials for solar cells.
A Novel Ligand Exchange Strategy
In this study, the research team developed a novel ligand exchange technique using an alkyl ammonium iodide-based strategy. This approach effectively substitutes ligands for organic PQDs, resulting in excellent solar utilization. The breakthrough enables the creation of a photoactive layer of QDs for solar cells with high substitution efficiency and controlled defects.
Improved Efficiency and Stability
The efficiency of organic PQDs, previously limited to 13% using existing ligand substitution technology, has been significantly improved to 18.1% with this new technique. Moreover, these solar cells demonstrate exceptional stability, maintaining their performance even after long-term storage for over two years. The newly-developed organic PQD solar cells exhibit both high efficiency and stability simultaneously.
Future Directions
The findings of this study present a new direction for the ligand exchange method in organic PQDs. This could serve as a catalyst to revolutionize the field of QD solar cell material research in the future. The research was made possible through the support of the ‘Basic Research Laboratory (BRL)’ and ‘Mid-Career Researcher Program,’ as well as the ‘Nano·Material Technology Development Program,’ funded by the National Research Foundation of Korea (NRF) under the Ministry of Science and ICT (MSIT). It has also received support through the ‘Global Basic Research Lab Project.’
