A new type of solar cell developed in Japan is drawing attention in Hong Kong, with a possible application to wearable devices.

Perovskite solar cells use a thin film of perovskite crystal combining metal atoms such as lead and organic substances such as bromine to generate current. Perovskite solar cells can be produced at low cost as they can be made simply by applying materials to print boards or other things.

In 2009, researchers at Japan’s Toin University of Yokohama confirmed that a thin film of perovskite crystal can function as a solar cell. The power conversion efficiency was initially less than 5%, but jumped to over 10% in 2012. Researchers and companies around the globe are competing to achieve higher power conversion efficiency.

A group of researchers, led by Hong Kong Polytechnic University professor Charles Chee Surya, invented perovskite-silicon tandem solar cells. With the perovskite solar cell functioning as the top layer, it can harvest the short-wavelength light, while the bottom layer coated with silicon is designed to absorb the long wavelength light.

The two layers enabled the module to achieve the “world’s highest” power conversion efficiency of 25.5%, according to Surya. Previously, the Swiss team’s 22.8% was the highest.

In addition to the usability of the material, the group estimates that power generation costs will be about 30% lower than with conventional silicon cells.

“The market for perovskite solar cells is going to grow quite substantially in the future,” said Surya. He explained that perovskite cells can be applied to a wide range of products, such as wearable devices and sensors for home appliances.

That said, there are safety and durability problems in putting perovskite solar cells into practical use. The use of lead, on which regulations have tightened around the globe, is raising concerns, and the power conversion efficiency, which declines in a few days, will also become a barrier to application. A joint effort between industry and academia will likely be the key to establishing mass production technology.

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