ULTRA-THIN ALUMINIUM OXIDE TUNNEL LAYER PASSIVATED CONTACT FOR HIGH-EFFICIENCY CRYSTALLINE SILICON SOLAR CELLS

Abstract

In order to boost the conversion efficiency of silicon solar cells, it is important to well evaluate and improve the surface passivation for both metalized and non-metalized areas. To passivate the metalized region, tunnel layer passivated contacts have been proposed. However, so far hole-selective contacts need further optimizations. This thesis first proposes an improved methodology to extract interface properties of dielectric layer passivated silicon wafers. Subsequently, atomic-layer-deposited ultra-thin aluminium oxide is investigated as a novel tunnel layer to form hole-selective contacts, where the thickness of aluminium oxide and its charge activation conditions are optimized. Stability of the ultra-thin aluminium oxide under illumination is also studied. Lastly, n-type silicon solar cells with passivated contacts using the optimized ultra-thin aluminium oxide as the tunnel layer are fabricated and an efficiency as high as 20.5% is achieved on a large cell area of 182 cm2.