Meet the Ultra-thin photovoltaics that are flexible enough to wrap around a pencil

Researchers in South Korea have developed flexible photovoltaic that could power wearable electronics like fitness trackers, smartwatches and smart glasses in future. The ultra-thin photovoltaics are flexible enough to wrap around the average pencil.

The researchers have presented the report results in the journal Applied Physics Letters, from AIP Publishing.

 “Our photovoltaic is about 1 micrometer thick,” said Jongho Lee, an engineer at the Gwangju Institute of Science and Technology in South Korea. One micrometer is much thinner than an average human hair.

Standard photovoltaics are usually hundreds of times thicker and even most other thin photovoltaics are 2 to 4 times thicker said the researchers.

The Scientists in South Korea made the ultra-thin solar cells from the semiconductor gallium arsenide. They embossed the cells right onto a flexible substrate without using an adhesive that would add to the material’s thickness. The cells were then “cold welded” to the electrode on the substrate by applying pressure at 170 degrees Celcius and melting a top layer of material called photoresist that acted as a temporary adhesive. The photoresist was later peeled away, leaving the direct metal to metal bond.

The metal bottom layer also served as a reflector to direct stray photons back to the solar cells. Researchers tested the efficiency of the device at converting sunlight to electricity and found that it was comparable to similar thicker photovoltaic. They performed bending tests and found the cells could wrap around a radius as small as 1.4 millimeters.

“The thinner cells are less fragile under bending, but perform similarly or even slightly better,” Lee said.

The transfer printing method developed by Lee and his colleagues may be used to make very flexible photovoltaics with a smaller amount of materials.