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New energy's thin ray of hope

Published on
Friday, July 8, 2011
Written by
Wong Yat-hei [1]

Many environmentalists and scientists will tell you that solar cells - which convert light energy into electricity by the photovoltaic effect - are the answer to the world's energy crisis and environmental problems. However, the high production cost has turned off many investors.

Professors Xiao Xudong and Li Quan, from the department of physics at the Chinese University of Hong Kong (CUHK), are determined to show the world that it is possible to commercialise solar cells on a big scale.

After two years of research with the support of CUHK, the Innovative Technology Council, the Chinese Academy of Sciences and the Shenzhen government, they successfully developed Cu(InGa)Se2 - or CIGS - which are thin film solar cells that are highly efficient but 50 per cent cheaper to produce than conventional crystalline silicon solar cells. 

"CIGS are believed to be the most economical and efficient solar cells in the near future," Xiao says. "My long-term goal is to develop cost-competitive CIGS production lines on the mainland and make the CIGS technology more accessible to the industry and the public. It is forecast that the market share of thin film solar cells will rise from its current 10 per cent to 35 per cent in the next 20 years."

CIGS have a conversion efficiency of 17 per cent - the highest among comparable solar cells in the Greater China region.

The research success can be traced to the perseverance of Xiao and his team. "Initially we set the goal to achieve an energy conversion efficiency of 10 per cent," he says. "At the start, we had no experience on how to measure the cell performance properly and faced many difficulties. The first sample we produced had an efficiency as low as 2.4 per cent.

"After two years of hard work, we surpassed our original goal and achieved a conversion efficiency of 17 per cent. Eventually, we worked it out, just like the Chinese saying: 'Nothing is difficult to the man who tries'."

Xiao points out that the mainland is one of the world's largest photovoltaic production centres with advantages in production chain, material cost and human resources. "To speed up the commercialisation plan, we start from the medium substrate size 10cm by 10cm rather than the lab size of 1cm by 1cm. The ultimate goal is to promote renewable energy and relieve the energy crisis and environmental problems," he says.

Installed on roofs and outer walls of buildings in Hong Kong, CIGS solar cells can potentially supply 40 per cent of the city's total electricity needs, reducing annual carbon emission by 15 million tonnes. It can also be used in handbags and backpacks to charge portable electronic products.

"The success of this project gives us the confidence that our design can be widely used in the commercial setting," Xiao says. "The next step is to seek the cooperation of the industry and commercialise the research findings. I believe the CIGS solar cell will be a major contribution in solar electricity in the future. I expect a very fast increase in market share."

Xiao concedes there are some hurdles ahead. "One potential obstacle [in the wide usage of CIGS solar cells] is the rising cost of raw materials, especially indium and selenium. But I expect technological progress to reduce raw material consumption in fabrication, while material demand will stimulate the mining process," he says.

Xiao, who has been doing research work in Hong Kong for 17 years, agrees that resources are not enough. However, he encourages researchers to keep working hard.

"Society provides the resources to researchers like us in the university, and I am very happy we can give back to society with research findings that are in the public interest," he says.


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