An international group of researchers led by University of Toronto Professor Ted Sargent has created the most efficient CQD solar cell the world has ever seen – with a record-breaking 7.0% efficiency.

CQD stands for colloidal quantum dot – a type of semiconductor only a few nanometres in size which is used to harvest electricity from the entire solar spectrum, including both visible and invisible wavelengths.

The findings, published in Nature Nanotechnology, are the result of work by the University of Toronto and King Abdullah University of Science & Technology (KAUST).
 
Unlike current slow and expensive semiconductor growth techniques, CQD films can be created quickly and at low cost, similar to paint or ink. This research paves the way for solar cells that can be fabricated on flexible substrates in the same way newspapers are rapidly printed in mass quantities.

The U of T cell represents a 37% increase in efficiency over the previous certified record. In order to improve efficiency, the researchers needed a way to both reduce the number of “traps” for electrons associated with poor surface quality while simultaneously ensuring their films were very dense to absorb as much light as possible. The solution was a so-called “hybrid passivation” scheme.
 
Work led by Professor Aram Amassian of KAUST showed that the organic ligand exchange was necessary to achieve the densest film.

This advance opens up many avenues for further research and improvement of device efficiencies, which could contribute to a bright future with reliable, low cost solar energy.