What is the meaning of this croped part? Why do they crop it, rather than let it be full square?
the monocrystalline cells are thinly sliced off cylindrically-grown single crystals that look like logs. Each wafer thus produced is hence a circular disc. To make the resulting solar cell function properly, its active area must be square so the rounded edges of the wafer get sawn off so the wafers can be packed together as closely as possible during bulk processing. The chamfered corners are left.