This sheet of paper, with an array of coloured rectangles printed over its surface, looks like any document that might have just come out of an office printer. But when a researcher picks it up, clips a couple of wires to one end and shines a light on the paper, an LCD clock display at the other end of the wires instantly starts to display the time.
Almost as easily as printing a photo on your inkjet printer, an inexpensive, simple solar cell has been created on a flimsy sheet, with special 'ink' deposited on the paper. One can fold it up, slip it into one's pocket, then unfold it and watch it generate electricity in the sunlight.
The new technology, developed by a team of researchers at the Massachusetts Institute of Technology (MIT), was reported in the Advanced Materials journal this month.
The technique, according to an MIT press release, represents a major departure from the current systems used to create most solar cells, which require exposing the substrates to potentially damaging conditions—liquids or high temperatures. The new printing process uses vapours, not liquids, and temperatures less than 120 degrees Celsius. The basic process is essentially the same as the one used to make the silvery lining in your bag of potato chips: a vapour-deposition process that can be carried out inexpensively on a commercial scale. The resilient solar cells function even when folded into a paper airplane.
In their paper, the researchers also describe printing a solar cell on a sheet of PET plastic (a thinner version of the material used for soda bottles) and then folding and unfolding it 1,000 times, with no significant loss in performance. By contrast, a commercially produced solar cell on the same material failed after a single folding.
In today's conventional solar cells, the costs of inactive components—the substrate (usually glass) that supports the active photovoltaic material, the structures to support that substrate, and the installation costs—are typically greater than the cost of the active films of the cells themselves, and sometimes twice as much.