Gallium-doped cells

Gallium-doped cells use gallium instead of boron as the dopant in p-type silicon wafers. This is a cell-level preventive measure against Light Induced Degradation (LID). Without boron atoms, boron-oxygen complexes cannot form in theory, and these complexes are the main LID mechanism. Since the industry moved to gallium, LID has become much less common and less severe. For nearly all current modules on gallium-doped p-type or n-type wafers it is of low relevance. Gallium-doped cells appear to be much less affected, or not affected at all, by both LID and light and elevated temperature induced degradation (LeTID). Moving from boron to gallium also reduced LeTID. Current TOPCon modules built on gallium-doped p-type wafers are expected to show no detectable LeTID at module or system level. The measure has limits: boron impurities left in the wafer can still cause LID in gallium-doped cells. Manufacturers combine the switch with adjusted cell processing, thinner wafers and fewer wafer impurities. On a project, check the bill of materials for the cell type, confirm with the manufacturer that the cells are stable, and ask for test reports that state the power loss.