Novel polysilicon in resisting thermal-evaporation Al-electrode damage and its application in back-junction passivated contact p-type solar cells.

ABSTRACT

In preparing tunnel oxygen passivation contact (TOPCon) solar cells, the metallization process often causes damage to passivation performance. Aiming to solve the issue, we investigated the advantages of the novel polysilicon, i.e. the carbon (C) or nitrogen (N) doped polysilicon, in resisting metallization damage. Our study reveals that C- or N-doped polysilicon does mitigate the passivation damage caused by the physical-vapor deposition metallization processes, i.e. the decrease in implied open-circuit voltage (iVoc) and the increase in recombination current (J0) are both suppressed. For the novel polysilicon samples suffered metallization, the decrease ofiVocwas only ∼-1 mV, and the increase ofJ0< 1 fA cm-2; in contrast, the decrease ofiVocof the standard polysilicon samples was -7 mV, and the increase ofJ0was ∼6 fA cm-2. In addition, we also explored the difference between the finger-metal and the full-metal metallization, showing that the finger-metal has less passivation damage due to the smaller contact area. However, the free energy loss analysis indicates that the advantage of the novel polysilicon in resisting metallization damage is overshadowed by the disadvantage of the higher contact resistivity when finger-metal electrodes are used. Numerical simulations prove that the efficiency of the solar cell with novel polysilicon still shows >0.2% absolute efficiency higher than that with the standard polysilicon, reaching 26% when full-metal electrodes by thermal evaporation.