Ultra-light solar cells may power next generation devices

New York, Feb 28 (IANS) Scientists from a US university have created the thinnest, lightest solar cells ever produced which could be placed on almost any material or surface including your hat, shirt, or smartphone, or even on a soap bubble.

Although it may take years to make such solar cells commercially available, the laboratory proof-of-concept shows their potential in helping power the next generation of portable electronic devices, believe researchers at Massachusetts Institute of Technology (MIT), who created it.

The process is described in a paper by MIT professor Vladimir Bulovi, research scientist Annie Wang, and doctoral student Joel Jean, in the journal Organic Electronics.

The key to the new approach is to make the solar cell, the substrate that supports it, and a protective over-coating to shield it from the environment, all in one process.

"The innovative step is the realisation that you can grow the substrate at the same time as you grow the device," Bulovi said.

In this initial proof-of-concept experiment, the team used a common flexible polymer called parylene as both the substrate and the over-coating, and an organic material called DBP as the primary light-absorbing layer.

Parylene is a commercially available plastic coating used widely to protect implanted biomedical devices and printed circuit boards from environmental damage.

The entire process takes place in a vacuum chamber at room temperature and without the use of any solvents, unlike conventional solar-cell manufacturing, which requires high temperatures and harsh chemicals. In this case, both the substrate and the solar cell are "grown" using established vapour deposition techniques.

The team said different materials could be used for the substrate and encapsulation layers, and different types of thin-film solar cell materials, including quantum dots or perovskites, could be substituted for the organic layers used in initial tests.

To demonstrate just how thin and lightweight the cells are, the researchers draped a working cell on top of a soap bubble, without popping the bubble.

Although cells may be too thin to be practical, but researchers said that parylene films of thicknesses of up to 80 microns can be deposited easily using commercial equipment, without losing the other benefits of in-line substrate formation.