The most efficient solar cell ever made based on collodial-quatum-dots (CQD) has been created by scientists from the University of Toronto, the King Abdullah University of Science and Technology, and the Pennsylvania State University.
Quantum dots are nanoscale semiconductors that capture light and convert it into an energy source. Because of their small scale, the dots can be sprayed on to flexible surfaces, including plastics.
This enables the production of solar cells that are less expensive to produce and more durable than the more widely known silicon-based version.
In the work, entitled “Collodial-quantum-dot photovoltaics using atomic-ligand passivation,” the researchers demonstrate how the wrappers that encapsulate the quantum dots can be shrunk to a mere layer of atoms.
“We figured out how to shrink the passivating materials to the smallest imaginable size,” Professor Ted Sargent, corresponding author on the work and holder of the Canada Research Chair in Nanotechnology at U of T said.
Finding a balance between convenience and performance, they found the ideal design is one that tightly packs the quantum dots together, as the greater the distance between quantum dots, the lower the efficiency.
To solve the problem, the researchers turned to inorganic ligands, which bind the quantum dots together while using less space. The result is the same colloid characteristics but without the bulky organic molecules.
“We wrapped a single layer of atoms around each particle. As a result, they packed the quantum dots into a very dense solid,” Dr. Jiang Tang, the first author of the paper who conducted the research while a post-doctoral fellow in The Edward S. Rogers Department of Electrical and Computer Engineering at U of T, explained.
The team showed the highest electrical currents, and the highest overall power conversion efficiency, ever seen in CQD solar cells.
The discovery has been reported in the latest issue of Nature Materials.