"China set anti-dumping import tariffs of up to 57% on U.S. polysilicon producers (such as REC Silicon and Hemlock Semiconductor) beginning on July 24, 2013 (following initial anti-dumping investigations and rulings announced in July 2013 and extended/reviewed in subsequent years)"
I worked for REC Silicon at the time and yes the Chinese did indeed do that. At first there were work-arounds but those were gradually closed down.
The REC polysilicon plant in Moses Lake WA (20,000 tons/year) is still there and has been shut down since 2019. They tried to restart it in 2024 but it supposedly couldn't meet the current quality standards. There was reportedly some skullduggery about the testing procedure but I can't speak to that as I retired in 2018.
Note that REC was not dumping polysilicon, I am well aware of their cost of production and their sales price. The fluidbed reactors were vastly more power efficient that the Siemens reactors. REC shut those down in 2013 if I remember right. The Butte plant ran them longer producing float-zone grade material until high power costs shut them down too.
The Chinese intend to be the monopoly supplier of PV panels, or at least 90% of them. They will and have done whatever is needed to achieve that.
It's the same policy as they have with rare earths, and EVs. Yes, "It's so cheap!" now, but eventually they will be yanking that supply chain.