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The Asahi Shimbun
Sci & Tech
article
By TAKUMI WAKAI/ Staff Writer
November 9, 2026 at 07:00 JST
Containers of iodine produced in Chiba Prefecture await shipment in a Godo Shigen Co. warehouse in Chosei, Chiba Prefecture, on Feb. 20. (Takumi Wakai)
CHOSEI, Chiba Prefecture—To power up the regional economy, Chiba prefectural officials are banking on locally produced iodine that is used in making perovskite solar cells.
Chiba Prefecture is a major, albeit little known, production center for iodine, which is being exported to the rest of the world.
A demonstration test for using perovskite solar cells on farmland recently commenced on Chiba University’s Kashiwanoha Campus in Kashiwa in the prefecture.
Officials are hoping the new technology will spread and be utilized for a broad range of uses.
Perovskite solar cells, which different nations of the world are vying to develop, are manufactured by applying ink-like material to film or glass.
They have the advantage of being so thin and lightweight that they can be installed, according to officials, on walls of buildings, windowpanes and other platforms.
They have, however, their own drawbacks, such as short lifespans and low durability.
The latest test uses film-type perovskite solar cells, which are flexible.
Perovskite solar cells weigh less than the conventional crystalline silicon solar cells, so they require significantly fewer support pillars when they are installed above farmland plots.
They are expected, for example, to allow a larger acreage to be set aside for cultivation and make it easier to drive farm machinery onto the plots, which could improve work efficiency.
The Chiba University test will run for three years, during which time officials will have perovskite solar cells installed above a rice paddy and study their power generation efficiency and their impact on rice yields.
‘KEY WEAPON’ FOR CARBON-FREE SOCIETY
Perovskite solar cells can be installed on building walls and other platforms that previously could not be used for photovoltaic power generation.
They are expected to spread rapidly as a “key weapon” for realizing a carbon-free society at a time when it is becoming difficult to build more mega solar farms, or large-scale photovoltaic power stations.
Fuji Keizai Co. expects the global market for perovskite solar cells to grow 2.3 times year on year to be worth 108.8 billion yen ($689 million) in 2026, partly because production lines by Chinese startups are entering into operation.
The research firm has projected the market to expand to 3.6854 trillion yen in 2040, as different manufacturers will enter into mass production in the years to come.
IODINE, MAIN INGREDIENT, IN SPOTLIGHT
Iodine, a main ingredient in the manufacturing of perovskite solar cells, is drawing attention amid advances in the development of the technology.
Japan is the world’s second-largest iodine producer after Chile, and Chiba Prefecture accounts for about 80 percent of Japan’s iodine production.
Iodine can be extracted from the South Kanto Gas Field, which stretches underground beneath Chiba Prefecture.
The element exists dissolved in brine groundwater that contains natural gas.
Iodine production in the prefecture is centered on the Kujukuri area, including the village of Chosei.
Demand for medical iodine is on the rise in the latest years due to the spread of advanced medical care in Asia.
The spread of perovskite solar cells is expected to provide a further boost to the industry.
Iodine producers based in Chiba Prefecture are therefore stepping up investments for increased production.
Ise Chemicals Corp., which has a 10-percent global share in iodine production, is investing more than 10 billion yen through 2028, partially to upgrade plant equipment in Chiba Prefecture.
The Tokyo-based company is also starting full-scale iodine production in the United States, and plans to increase its annual output from the current 4,000 tons or so to about 7,500 tons by the end of 2030.
K&O Iodine Co., based in Shirako, Chiba Prefecture, is also making a capital investment with the goal of increasing its annual output from the current 1,650 tons or so to more than 2,000 tons in the 2030s.
OBSTACLES TO OUTPUT INCREASE
Pumping up large volumes of brine, however, could cause ground subsidence, so limitations have been set on the amount of surface drainage on an area-by-area basis.
The producers have signed an agreement with the prefectural government, on the basis of which they are returning water to the underground after extracting natural gas and iodine from it.
The system setup means that more water could be pumped up, and more iodine could be produced, if only more water were to be returned. That, however, is easier said than done.
“The ground is too firm for water to penetrate easily,” an industry insider said. “Just because there is more demand doesn’t mean you can increase output all at once, so long as there is no technological innovation.”
Godo Shigen Co. is therefore putting much effort into the recycling of spent iodine.
The iodine producer, based in Chosei, has released a plan for increasing its output of recycled iodine by 300 tons over the next three years.
“Iodine is one of the few resource materials that Japan is exporting,” said Yasuhiko Otani, president of Godo Shigen. “We hope to take into account the growth of new demand and aggressively make capital investments.”
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