Yes, that is true. In fact, half of the polysilicon, which is the main raw material used to make solar wafers, is produced in highly secretive coal-powered factories in the Xinjiang region. It's the same place the communist regime is carrying out a genocide against the Muslim minority.
I'm going to quote Reuters here:
Some U.S. lawmakers have voiced gorwing [sic] concern that the industry is dependent upon products, specifically the raw material polysilicon, linked to work camps in China’s Xinjiang region. The U.S. State Department has made a determination that Chinese officials are perpetrating genocide there, and imports of cotton and tomato products from the region were banned this year.
Will you make the commitment on behalf of Brookfield that you will not source any materials from the Xinjiang region?