Hydrogen fluoride (HF) is used in the solar cell fabrication. The cells will later be used in the solar panels.
The solar panels are made of silicon photovoltaic cells. In order to gather as much sun energy (photons) as possible, the cell should be free from oxides and other impurities that might interfere in this process. Therefore a high purity quality of HF (ppb impurities level) is required for this cleaning process.
Furthermore, in order that the sun energy stays in the cell surface and does not rebound back (thus losing the possibility to convert it into electricity), the HF can also create small “mountains” in the cell surface, so that the photons stay in the cell surface for longer. This process is called texturization.