SolarCity, whose largest shareholder is Tesla Motors’ Elon Musk, is currently constructing North America's largest module factory in Buffalo, New York.

At the heart of the case is a disagreement as to whether the modules SolarCity will make in New York are based on thin-film or crystalline silicon (c-Si) PV technology.

The difference is crucial. The US has imposed significant trade duties on Chinese c-Si cells and modules; Chinese thin-film PV products, however, are exempt from the duties.

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