With the recent development of foldable cell phone screens, research into foldable electronics has never been so intense. One particularly useful application of the foldable technology is in solar panels.
Current solar cells are limited to rigid, flat panels that are difficult to store in large numbers and incorporate into everyday devices such as phones, windows, vehicles, or indoor devices. One problem, however, is preventing this formidable technology from breaking through: to be incorporated into these elements, solar cells must be foldable and bend repeatedly at will without breaking. Conventional conductive materials used in solar cells are not flexible enough, which is a major obstacle to the development of fully foldable cells.
A key requirement for an efficient foldable ladder is the ability to withstand bending pressure within a very small radius while maintaining its integrity and other desirable properties. In short, a thin, flexible, transparent and elastic conductor material is needed. Professor Il Jeon from Pusan National University, Korea explains: “In contrast to purely flexible electronics, foldable devices with folding radii of only 0.5 mm are subject to much greater deformations. This is not possible with conventional ultra-thin glass substrates and metal oxide transparent conductors, which can be made flexible, but are never fully foldable. “
Fortunately, an international team of researchers, including Prof. Jeon, found a solution in a study published in Advanced Science. They identified a promising candidate to meet all of these requirements: single-walled carbon nanotube films (SWNT) due to their high transparency and mechanical strength. The only problem is that SWNTs have difficulty adhering to the substrate surface when subjected to force (e.g., bending) and require chemical doping. To address this problem, the scientists embedded the conductive layer in a polyimide (PI) substrate and filled the voids in the nanotubes.
To ensure maximum performance, they also “doped” the resulting material to increase its conductivity. By introducing small impurities (in this case, withdrawn electrons in molybdenum oxide) into the SWNT-PI nanocomposite layer, the energy it takes electrons to move across the structure is much less and therefore more charge can be generated for a given amount of current .
The resulting prototype far exceeded the team’s expectations. The composite film, which was only 7 micrometers thick, showed exceptional flexural strength, a transparency of almost 80% and a power conversion efficiency of 15.2%, the highest value ever achieved in solar cells with carbon nanotube conductors! As Prof. Jeon emphasized, “the results achieved are among the best that have been reported for flexible solar cells so far, both in terms of efficiency and mechanical stability.”
With this novel breakthrough in solar harvesting technology, one can only imagine what next-generation solar panels will look like.
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Materials provided by Pusan National University. Note: The content can be edited by style and length.