Researchers at the Pennsylvania State University, King Abdullah University of Science & Technology (KAUST) and University of Toronto (U of T) have designed a colloidal-quantum-dot solar cell with a record conversion efficiency using atomic-ligand passivation method.
The researchers have presented a paper titled ‘Colloidal-quantum-dot photovoltaics using atomic-ligand passivation’ in the journal Nature Materials. Quantum dots, which are semiconductors at the nanoscale, capture light and transform it into a source of energy. As the colloidal quantum dots are very small, their nanoscale allows their coating over flexible surfaces such as plastics. This allows the production of cheaper solar cells with better durability compared to silicon-based solar cells.
In the paper, the researchers have demonstrated how they have shrunk the sheaths that cover the quantum dots to atomic thick layers. The more the gap between the quantum dots, the lesser is the efficiency of the solar cell. Hence, an optimal design is one that closely packs the quantum dots with each other. To achieve this, the researchers have utilized inorganic ligands that bind the quantum dots tightly, while utilizing minimal space.
Dr. Jiang Tang, a member of the research team, commented that the researchers sheathed each particle by a single layer of atoms, causing the quantum dots to be packed as a highly dense solid. The researchers demonstrated maximum electrical currents and maximum overall power conversion efficiency that had not been possible in existing colloidal-quantum-dots solar cells. A Newport-based external laboratory under the accreditation of the US National Renewable Energy Laboratory certified the performance results.
John Asbury, a member of the research team, stated that the research team demonstrated that it can eliminate charge traps when electrons get trapped, while tightly packing the quantum dots together. The combination of tight packing and elimination of charge traps allowed electrons to transport quickly and smoothly via the solar cells, resulting in record conversion efficiency.
Professor Dmitri Talapin of The University of Chicago stated that this discovery demonstrates the significance of inorganic ligands in designing practical devices. This novel surface chemistry paves the way for the development of stable and efficient quantum dot solar cells and also has an impact on colloidal nanocrystal-based electronic and optoelectronic devices, he said.
Professor Aram Amassian of KAUST stated that the research team demonstrated that inorganic passivants were closely connected with the position of the quantum dots and it is a novel method to chemical passivation instead of nanocrystal ordering, causing the record-breaking performance of the colloidal quantum dot solar cell.