A research team led by Ted Sargent, a professor of electrical and computer engineering at the University of Toronto in Canada, has developed a colloidal quantum dots (CQD) double-layer solar cell for the first time. It is made of light-absorbing nanoparticles called quantum dots. It can absorb not only visible light but also invisible light, and its theoretical conversion efficiency can be as high as 42%, exceeding the theoretical conversion rate of 31% of existing ordinary solar cells. Related research papers were published in Nature Photonics.
Quantum dots have been regarded as a promising method to prepare low-cost solar cells because these particles can be sprayed onto various surfaces. However, the battery efficiency based on this technology is too low to be practical. In a double-layer solar cell developed by researchers at the University of Toronto, one layer of quantum dots can be modulated to capture visible light, while the other layer captures infrared light. The researchers also introduced a transition layer consisting of four different film-like metal oxides. This method reduces the interlayer resistance. They chose a transparent oxide for this layer, so that light can pass through them and reach the underlying cell.
The conversion efficiency of the solar cell currently developed by the researchers is 4.2%. Professor Sargent pointed out that this method can be used to manufacture 3-layer or even 4-layer solar cells. The team's goal is to achieve an efficiency of more than 10% within 5 years, and then continue to improve.
John Asbury, a professor of chemistry at Pennsylvania State University, pointed out that because of the ability to make multilayer quantum dot solar cells, the University of Toronto team increased the theoretical efficiency from 30% to over 40%. However, to develop solar cells of any scale close to this efficiency, it is necessary to eliminate the binding state problem.
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