Assisted passivation by a chemically grown SiO2 layer for p-type selective emitter-passivated emitter and rear cells

Abstract

This paper presents the development of industrial-sized p-type passivated emitter and rear cells (PERCs) with a selective emitter (SE) structure. We focus on different assisted passivation schemes and use nitric acid oxidation of silicon (NAOS) to form an ultrathin SiO2 layer. The results show that all I–V parameters of the PERCs are significantly modified when SiO2 is present on the front and/or rear sides of the cell. For front-emitter passivation by NAOS-SiO2, we observe an increase in the open-circuit voltage (Voc) and short-circuit current density (Jsc) and strong enhancement of the internal quantum efficiency (IQE) for short-wavelength photons. This can be attributed to the high level of chemical passivation, as indicated by the reduced interface trap density (Dit), due to the reduced Shockley–Read–Hall recombination. By contrast, all I–V parameters associated with SiO2 rear passivation decrease due to the increased Dit, which results in enhanced surface recombination. The different types of surface passivation for n-type (front) and p-type (rear) surfaces are presumably due to different doping surface concentrations. These results suggest that NAOS surface pretreatment is a very promising technique to improve the level of surface passivation and thereby enhance the performance of industrial-sized PERCs.