TOPCon (Tunnel Oxide Passivated Contact) – oxide layer passivated contact. There is no essential difference between the front side and conventional N-type solar cells or N-PERT solar cells, and the core technology of the battery is the passivation contact on the backside. The back of the battery is composed of a layer of ultra-thin silicon oxide (1~2nm) and a layer of phosphorus-doped microcrystalline amorphous mixed Si film, which together form a passivation contact structure. The passivation performance is activated by the annealing process, and the crystallinity of the Si film changes during the annealing process, from microcrystalline amorphous mixed phase to polycrystalline. Annealed at an annealing temperature of 850°C, iVoc>710mV, J0 in 9-13fA/cm2, showing excellent passivation performance of passivated contact structure.

This structure can prevent the recombination of minority carriers and holes, and increase the open circuit voltage and short circuit current of the battery. The ultra-thin oxide layer can allow many electrons to tunnel into the polysilicon layer while blocking the recombination of minority electrons and holes. The good passivation effect of ultra-thin silicon oxide and heavily doped silicon film makes the surface energy band of the silicon wafer bend, thus forming field passivation As a result, the probability of electron tunneling is greatly increased, the contact resistance is reduced, and the open circuit voltage and short circuit current of the battery are increased, thereby improving the conversion efficiency of the battery.