Effect of substrate heating on the adhesion and humidity resistance of evaporated MgF 2/ZnS antireflection coatings and on the performance of high-efficiency silicon solar cells

Abstract

This paper reports experimental results with substrate heating during thermal evaporation of MgF 2/ZnS DLAR (double-layer antireflection) coatings. The higher substrate temperature significantly improves the adhesion and humidity resistance of such coatings, while marginally reducing the performance of high-efficiency silicon PERL (passivated emitter, rear locally diffused) cells. The optimum substrate temperature for the evaporation of such DLAR coatings on the PERL cells is about 150°C. At this temperature, the DLAR coatings have good durability, but give only slightly reduced PERL cell performance compared to the unheated substrate case. This reduction in the PERL cell performance is believed due to the partial removal of the hydrogen passivation, which was introduced through a standard “alneal” (aluminium anneal) process.