Optimisation of saw damage removal to reduce interface recombination losses
The complete removal of the saw damage decreases density of states in the near surface region is an important precondition to reduce recombination losses in solar cells. In order to avoid expensive and time consuming lapping and polishing processes, wet-chemical etching procedures in alkaline potassium hydroxide (KOH) solution are preferred in solar cell manufacturing, to remove saw damage from the as-cut wafers.
Saw Damage Etching (SDE) decreases step-wise the recombination losses. Too long SDE, however, increases surface defects and recombination losses due to inhomogeneous etching and initial formation of random pyramids. The etching time influences the saw etching dept, as well as the emerging Si surface morphology. Therefore, the SDE process has to be carefully optimised with respect to the kind of Si substrate manufacturing.
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