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RESEARCHERS from the University of Toronto and King Abdullah University of Science & Technology have made a breakthrough in the development of colloidal quantum dot (CQD) films.
This breakthrough has led to the most efficient low-cost CQD solar cell ever, with a 7.0 percent efficiency, representing a 37 percent increase on efficiency over the previous certified record.
Previously, quantum dot solar cells have been limited by the large internal surface areas of the nanoparticles in the film, which made extracting electricity difficult. The researchers used a combination of organic and inorganic chemistry to completely cover all of the exposed surfaces.
Quantum dots are semiconductors only a few nanometres in size and can be used to harvest electricity from the entire solar spectrum – including both visible and invisible wavelengths.
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.
In order to improve efficiency, the researchers found 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.
By introducing small chlorine atoms immediately after synthesising the dots, they researchers “patched” the previously unreachable nooks and crannies that lead to electron traps.
The advance opens up many avenues for further research and improvement of device efficiencies, which could contribute to a future with reliable, low cost solar energy.