Seoul (PTI): In a major breakthrough that can speed up commercial use of solar energy, South Korean scientists on Monday announced the development of a highly efficient plastic-based power cell that can mimic the photo-photovoltaic activities of plants.

The team led by Lee Kwang-hee at the Gwangju Institute of Science and Technology (GIST), said the solar cells developed by them reached an unprecedented energy efficiency rate of 6.2 per cent.

"This is the highest number reached by any single-layer plastic, organic photo-voltaic solar cell created in the world to date and should greatly help commercial use of power generation using sunlight," Lee, a material science professor at the state-run laboratory, said.

The scientists said they used a new material that have "open circuit voltage" properties and titanium oxide to bring about high efficiency.

If fully developed the solar cells, which can easily bend, could be attached to coats, bags, various electronic appliances and building windows, Yonhap news agency reported.

The breakthrough has been confirmed by the U.S. National Renewable Energy Laboratory and published in the latest on- line edition of international journal of Nature Photonics.

Lee said that under so-called green light conditions, the energy efficiency of the new plastic power cells reached 17 per cent, which is more than enough to start commercial power generation.

Experts said an efficiency rate of 7 per cent must be reached for plastic solar cells to become commercially viable.

Energy efficiency indicates the percentage of sunshine that solar cells turn into electricity.

Conventional inorganic silicon-based solar cells used in homes have an efficiency rate of 7 to 8 per cent, while very expensive panels placed on satellites have numbers reaching 15 per cent.

The technology, developed jointly with U.S. researchers led by Alan Heeger of the University of California, Santa Barbara, is an extension of cutting edge research carried out in the past.

The Lee-Heeger team announced in 2007 that they had built a stacked or double-layered organic photo-voltaic that had a power efficiency of 6.5 per cent.