Research team develops world’s most efficient quantum dot solar cells

A breakthrough in solar energy research has propelled the development of the world’s most efficient quantum dot (QD) solar cell, marking an important step toward the commercialization of next-generation solar cells. This cutting-edge QD solution and device has demonstrated exceptional performance, maintaining its effectiveness even after long-term storage.

Led by Professor Sung-Yeon Jang from UNIST’s School of Energy and Chemical Engineering, a team of researchers has unveiled a new ligand exchange technique. This innovative approach enables the synthesis of perovskite quantum dots (PQDs) based on organic cations, ensuring exceptional stability while removing internal defects in the photoactive layer of solar cells.

The results of this study, co-authored by Dr Javid Aqoma Khoiruddin and Sang-Hak Lee, were published online in Natural energy.

“Our developed technology achieved an impressive efficiency of 18.1% for QD solar cells,” said Professor Jang. “This remarkable achievement represents the highest efficiency among quantum dot solar cells recognized by the prestigious National Renewable Energy Laboratory (NREL) in the United States.”

The growing interest in related fields is evident since last year three scientists who discovered and developed QDs, as advanced nanotechnology products, were awarded the Nobel Prize in Chemistry.

QDs are semiconductor nanocrystals with typical dimensions ranging from several to tens of nanometers, capable of controlling photoelectric properties depending on their particle size. PQDs, in particular, have attracted the attention of researchers due to their exceptional photoelectric properties.

Additionally, their manufacturing process involves a simple spraying or application on a solvent, eliminating the growth process on substrates. This streamlined approach enables high-quality production in diverse manufacturing environments.

However, the practical use of QDs as solar cells requires technology that reduces the distance between QDs through ligand exchange, a process that binds a large molecule, such as a ligand receptor, to the surface of a QD.

Organic PQDs face notable challenges, including defects in their crystals and surfaces during the substitution process. As a result, inorganic PQDs with limited efficiency of up to 16% have been mainly used as materials for solar cells.

In this study, the research team used an alkylammonium iodide-based ligand exchange strategy, effectively substituting ligands for organic PQDs with excellent solar utilization. This breakthrough enables the creation of a photoactive layer of QDs for solar cells with high substitution efficiency and controlled defects.

Therefore, the efficiency of organic PQDs, previously limited to 13% through existing ligand substitution technology, has been significantly improved to 18.1%. Additionally, these solar cells demonstrate exceptional stability, retaining their performance even after long-term storage for more than two years. The newly developed PQD organic solar cells feature high efficiency and high stability simultaneously.

“Previous research on QD solar cells mainly used inorganic PQDs,” said Sang-Hak Lee, the first author of the study. “Through this study, we demonstrated the potential in addressing the challenges associated with organic PQDs, which have proven difficult to use. »

“This study presents a new direction for the ligand exchange method in organic PQDs, serving as a catalyst to revolutionize the field of QD solar cell materials research in the future,” said Professor Jang.