The spot-like defect on aluminum oxide passivation layer for crystalline silicon wafer

Defects such as dislocations and grain boundaries generally govern the efficiency of silicon-based solar cells. The use of a proper passivation layer can substantially increase the energy conversion efficiency. In this study, spot-like defects on the aluminum oxide passivation layer were observed. The formation and variation of spot-like defects were found to be affected by the thermal annealing temperature of the passivation surface. The density of spot-like defects was varied from 1.92 × 10⁴ /cm² to 3.13 × 10⁵ /cm² at different annealing temperature. Furthermore, the numbers of spot-like defects were affected by the heating and cooling speed. For the purpose of obtaining high minority carrier lifetime and low hillock defect density simultaneously, using a lower heating and cooling speed in thermal annealing process was suggested. In this study, the obtained minority carrier lifetime and density of spot-like defect with an optimized annealing condition were 166 μs and 8.84 × 10³/cm², respectively.