Over-production of solar panels in the world market has caused intense competition and driven down prices. As a result, many manufacturers have gone under or are struggling to survive, the Wall Street Journal reports.

Over the past several months, at least seven solar-panel manufacturers have filed for bankruptcy or insolvency, including two German companies in the past week—Solar Millennium AG and Solon SE—and, most notably, Solyndra LLC, the Fremont, Calif., company embroiled in a criminal investigation into whether the company defrauded the U.S. government.

Meanwhile, the average price of solar panels has plunged. 

Read about the “dark times” that have fallen on the solar industry here.