Summary of Quantum Dot Solar Cells Break Conversion Efficiency Record
MIT researchers achieved 9% efficiency in colloidal quantum dot solar cells using room-temperature solution processing. This method eliminates the need for high temperatures or vacuum conditions, utilizing ligand treatments to align energy bands and enhance charge transport while maintaining stability in air.
Parts used in the Quantum Dot Solar Cell:
- Colloidal quantum dots
- Ligands (molecules or ions binding to central metal)
- Solution-based precursors
- Electrodes
Quantum dots have offered an attractive option for photovoltaics. Multijunction solar cells made from colloidal quantum dots (CQD) have been able to achieve around 7-percent conversion efficiency in the lab. While figures like this may not seem too impressive when compared to silicon solar cells, their promised theoretical conversion efficiency limit is an eye-popping 45 percent. This is possible because when a single photon is absorbed by a quantum dot, it produces more than one bound electron-hole pair, or exciton, thereby doubling normal conversion efficiency numbers seen in single-junction silicon cells.
Now researchers at the Massachusetts Institute of Technology (MIT) have raised the bar for quantum dot-based solar cells by producing one that changes light to electricity with 9-percent conversion efficiency. Furthermore, says the MIT team, it can be produced using an inexpensive production method that promises to keep manufacturing costs down.
The researchers, who published their findings in the journal Nature Materials, hit upon a way to produce quantum dot solar cells through a solution processing technique that doesn’t require high temperatures or a vacuum atmosphere to achieve stability for the solar cells when they are exposed to air. By using ligand treatments, which involve molecules or ions that bind to a central metal, the researchers were able to align the bands of the quantum dot layers, improving the performance of the films.
“Every part of the cell, except the electrodes for now, can be deposited at room temperature, in air, out of solution. It’s really unprecedented,” said graduate student Chia-Hao Chuang in a press release.
The processing technique for the quantum dot layers allows for the dots to do what they do well individually and also to work together in the transport of electrical charge to the edges of the film where it can then be collected to provide an electrical current.
For more detail: Quantum Dot Solar Cells Break Conversion Efficiency Record
- What conversion efficiency did MIT researchers achieve?
The team produced a cell with 9-percent conversion efficiency. - How do quantum dots improve efficiency compared to silicon?
A single photon absorbed by a quantum dot produces more than one bound electron-hole pair, doubling normal conversion numbers. - Does the production method require high temperatures?
No, every part except the electrodes can be deposited at room temperature. - Is a vacuum atmosphere necessary for this process?
No, the technique works without a vacuum atmosphere and achieves stability when exposed to air. - What role do ligand treatments play in the project?
Ligand treatments involve molecules that bind to a central metal to align the bands of quantum dot layers and improve film performance. - Can the quantum dot layers work together for charge transport?
Yes, the processing allows the dots to work together to transport electrical charge to the edges of the film for collection. - What journal published these findings?
The researchers published their findings in the journal Nature Materials.
