Thin-film solar cells are pliable and can be bent or folded. They can be installed not only in road lamps, garden lights or traffic lights, but also in cars, umbrellas and clothes.

If thin-film photovoltaic technology is applied to the glass walls of buildings in the future, the building will generate solar power at a cost that is only 20 percent more than the cost of a regular glass wall, said Shi.

Some people like Zhou Tao, an analyst studying the photovoltaic cell market at a security company, imagine highways paved with thin-film solar cells. Photovoltaic stations could be built every 100 km along the highway, where cars would "fill up" on electricity instead of gasoline.

"In the desert of west China, it would only cost 0.5 yuan (less than $.10) to generate 1 kwh of electricity with thin-film solar cells. The price of solar power is competitive with that of hydro and thermal power," said Han Xiaoping, the information director at energy market analysis website www.china5e.com .

Currently, low photovoltaic efficiency rate and high production cost of thin-film solar cells hamper its popularization, but scientists believe all these problems can be solved.

Inspiration from plants

Every second, some 800,000 kw of solar energy reach the earth. The energy brought by the sun to Earth in one hour is enough to meet the human energy demand for one year.

The key to harness solar energy is to improve the efficiency of solar cells. Plants can harvest solar energy and store it through the photosynthetic process, which scientists are keen to simulate.

Light harvesting is the most basic step in photosynthesis. All plants have light-harvesting pigments, which scientists call "antennae." Even algae living in the darkness of the deep sea can capture dim light with a light-harvesting pigment complex.

To improve the efficiency of photovoltaic cells, scientists are working on a new type of solar cell with light-harvesting antennae.

In the eyes of these scientists, the photosynthetic process is the model for efficiency in using solar energy. In fact, fossil energies such as oil, coal and natural gas are the direct and indirect products of the photosynthetic process.

"Each year 220 billion tons of bio-energy is produced through photosynthesis, which is 10 times the energy needed for human consumption," said Kuang Tingyun, an academician at the CAS. According to Kuang, in the first phase of photosynthesis, the light-harvesting pigment protein complex in a plant's chloroplast can absorb and transfer 90 to 98 percent of the light's energy. That energy is then transferred to the plant's reaction center, where the quantum efficiency reaches 100 percent. "The whole energy absorption process takes seven to 15 seconds," Kuang said.

In 2004, the science journal Nature published an article on the crystal structure of spinach's major light-harvesting complex. The research was jointly carried out by the Institute of Biophysics and the Institute of Botany, both under the CAS. The article suggests that scientists have identified the crystal structure of light-harvesting complexes and deciphered the light energy absorption and transfer process. This has provided the possible foundation for people to mimic photosynthesis.

"After getting the structure of light harvesting pigment proteins, we can make bio-chips from it, which can be used to produce chlorophyll solar cells with high solar efficiency," said Kuang.

Currently, the CAS' Institute of Botany, Institute of Chemistry and Institute of Technical Physics, as well as the National Nano Center, are developing biological photovoltaic cells. And not long ago, researchers at the East China Normal University produced a highly efficient solar cell by simulating the energy absorption process of a plant's chloroplast.