The world’s most efficient quantum dot (QD) solar cell has been developed by the Ulsan National Institute of Science and Technology (UNIST). A quantum dot solution and a device used in the development of the solar cell can maintain high performance even after long-term storage, taking a step closer to the commercialization of next-generation solar cells.
A team led by professor Jang Jang-yeon of the Department of Energy and Chemical Engineering at UNIST has synthesized highly stable organocation-based perovskite quantum dots and developed a new ligand substitution technology to suppress internal defects in photoactive thin films for solar cells, according to UNIST.
“Based on this technology, we achieved efficiency of 18.1 percent for quantum dot solar cells, which is the world’s highest efficiency for the technology certified by the National Renewable Energy Laboratory in the United States to date,” said Prof. Jang.
According to the team, quantum dots are very small semiconductor crystals ranging in size from a few to tens of nanometers with optoelectronic properties that can be tuned by the size of particles. In particular, perovskite quantum dots have excellent photoelectric properties.
Instead of growing them on a plate, solar cells can be produced by spraying or applying them with a solvent. This makes it possible to produce consistent quality in a relatively simple way, unaffected by its production environment.
To utilize quantum dots as solar cells, a technology is needed to reduce distances between quantum dots by substituting ligands on their surface. Ligands are substances that specifically bind to large molecules such as receptors.
A substitution process causes significant crystal and surface defects in organic perovskite quantum dots. Until now, they have had no choice but to use inorganic perovskite quantum dots with an efficiency limited to 16 percent as materials for solar cells.
The research team developed a new ligand substitution method utilizing alkylammonium-based molecules for the effective ligand substitution of organic perovskite quantum dots with excellent solar utilization. The team could obtain a quantum dot photoactive layer for solar cells with high substitution efficiency and controlled defects.
As a result, the efficiency of organic perovskite quantum dot solar cells with up to 13 percent efficiency by conventional ligand substitution technology climbed to 18.1 percent. It maintained the same performance even after long-term storage for more than two years, showing high utilization.
This confirms that the newly developed organic perovskite quantum dot solar cells are both highly efficient and stable.
Dr. Havid Aqoma Khoiruddin and Lee Sang-hak, a researcher in the Integrated Master’s and Doctoral Program, served as co-first authors of the study. The study results were published online in Nature Energy on Jan. 27.