Solar cells are getting better at harvesting energy from the sun and turning that into electricity. But because they're made from plastic or glass, solar cells are bulky and stiff, which limits where they can be used. That's about to change. A group at Stanford University
has made a photovoltaic cell that can be peeled off of a backing like a sticker
and attached to any surface.
The researchers, lead Xiaolin Zheng, assistant professor of
mechanical engineering, started with the foundational material for conventional solar cells — the silicon dioxide wafer. Silicon releases electrons when light hits it and its those electrons that are captured and used for electricity. Typically, the wafers are thick and stiff and not flexible at all. But Zheng and her team had a plan.
First, they laid down a 300-nanometer
film of nickel on top of the wafer. Next, they coated it with a
protective plastic. The result was a super-thin layer of
plastic on top of the silicon dioxide wafer. Those three layers are the necessary active ingredients of a working solar cell. But in this stage, the solar cell is still thick and rigid.
So, the research put a layer of thermal release tape on top. Then they then dipped the whole thing in room-temperature water. By tugging
back on the thermal release tape, they were able to
peel back a very thin, three-layered "sandwich" of plastic, nickel and silicon dioxide — leaving behind most of the silicon dioxide wafer.
The ultrathin three-layered sandwich was so thin that it could flex. And because the process removed only a nanometer-scale layer of silicon dioxide, the wafer could be used again in the same process to make more super-thin solar cell sandwiches. That would reduce waste at solar cell manufacturing plants.
But the researchers didn't stop there. Zheng's group then heated the solar cell to about 194 degrees Fahrenheit
to make it soft enough to take on any shape and attach to any surface. In order to work, it would still need to be connected to electrodes and other components that would ultimately allow the harvested sunlight to be used as electricity.
The method Zheng and her team came up with would work
on conventional electronics as well as unconventional ones, such as clothing. In the meantime, it will be nice to fuel a phone from the
sun rather than worrying about battery life.
Credit: Chi Hwan Lee, Stanford University