Surface passivation of crystalline silicon by sputtered AlO_x/AlNx stacks toward low-cost high-efficiency silicon solar cells

Recently, excellent surface passivation has been achieved for both p- and n-type silicon solar cells using AlO_x/SiNx:H stacks deposited by atomic layer deposition and plasma-enhanced chemical vapor deposition. However, alternative materials and deposition methods could provide practical options for large-scale manufacturing of commercial solar cells. In this study we demonstrate that AlO_x/AlNx stacks fabricated by reactive radiofrequency magnetron sputtering can provide fairly good surface passivation (S_max of ∼30cm/s) regardless of AlO_x thickness, which is found to be due to the high negative fixed charge density (Qeff of -2.8 × 10¹²cm^-2) and moderately low interface trap density (Dit of 2.0 × 10¹¹ eV^-1.cm^-2). The stacks also show fairly good antireflection performance in the visible and near-infrared spectral region. The demonstrated surface passivation and antireflection performance of in situ reactively sputtered AlO_x/AlNx stacks make them a promising candidate for a surface-passivating antireflection coating on silicon solar cells.