A team at the Massachusetts Institute of Technology has unveiled the lightest, thinnest solar cells in existence — so lightweight and flexible that they can be placed on top of a soap bubble without popping it. The breakthrough came about when researchers realized they could create the solar cell, the substrate that protects it, and a protective overcoating in a single process, rather than creating them separately and joining them together later.
To prove the process was possible, the team used a flexible polymer called parylene as the substrate and overcoating. The primary light-absorbing layer was made of an organic material called DBP. Parylene has been widely used as a plastic coating to protect biomedical devices and circuit boards from the elements, making it perfect for the task of protecting the solar cells. The entire process was carried out in a vacuum chamber at room temperature without any harsh chemicals — a major change from conventional solar-cell manufacturing, which involves high temperatures and strong solvents.
The team says that this process could easily be repeated using different substrate and protective layers, and even different types of solar film. The end result is a flexible film just one-fiftieth the thickness of a human hair, about two micrometers thick. That’s about a thousand times thinner than an equivalent solar cell on a glass substrate, and by all accounts, these ultra-thin cells work just as efficiently to generate electricity.
While it’s possible to drape the new solar cell over a bubble without popping it, that might not be very practical for most applications — the light weight of the material also makes it easy to simply blow away. However, thicker parylene films can also be made using the same technique, and these might be possible to manufacture and directly apply to variety of household items and surfaces without adding extra weight or bulk. For now, the MIT team is doing further research before attempting to use the cells in any commercial applications.