N-type has high requirements for crystal quality and oxygen carbon content. The typical problem is the concentric circle and black chip problem caused by native oxygen. The reason for this is that the high-temperature silicon solution undergoes relatively high-speed convection in the crucible. Because the outside is hot and the middle is cold, and the bottom is hot and the top is cold, the silicon solution inside the crucible will form a "boiling" phenomenon, causing the silicon solution to flow inside and constantly wash the quartz crucible. Quartz is silicon dioxide, and the oxygen contained in it will merge into the silicon solution during the flushing process, resulting in a higher amount of oxygen in the crystal.

Under the subsequent high-temperature process of TOPCon (such as B diffusion), oxygen is easily precipitated, forming oxygen rings or concentric circles, which affects efficiency and yield. Therefore, TOPCon is more sensitive to the oxygen content of silicon wafers; HJT is a low-temperature process, and the probability of concentric circles appearing is not high. High oxygen content silicon wafers can be selected.