Analysis and optimization of alloyed Al-p+ region and rear contacts for highly efficient industrial n-type silicon solar cells

Abstract

This paper aims to develop high quality screen-printed Al emitters and improve the interface condition of rear contacts in industrial silicon solar cells. We propose to introduce an ultra-thin SiO₂ buffer layer between the silicon bulk and metal contact during the fabrication process. A post-annealing strategy is adapted to further modify the Al doping profiles. The experimental results show that the effects of this oxide layer on migrating the nonuniformity of Al-p⁺ region and decreasing the defects at the metal–silicon interface are significant. The recombination velocity of contacts, which is extracted from the measured S_rear by an analytical model, exhibits a decrease by 90.8% and the series resistance is reduced by 60.3% for the improved contacts compared to the conventional screen-printed contacts. Finally, this technique is applied to large-area (156 × 156 mm²) industrial n-type silicon solar cells and leads to a 2.18% increase in average cell efficiency, including a 12.82 mV increase in open-circuit voltage V_oc and 0.99 mA cm⁻² increase in short-circuit current density J_sc compared with solar cells fabricated by a standard industrial process. A 19.16% efficient cell with a V_oc of 637.47 mV is achieved.