Rear-side passivation characteristics of Si-rich SiNx for various Local Back Contact solar cells

•Si-rich SiNx film with low fixed charge density 1.63 × 1012 cm−2 employed for rear passivation.•Rear SRV and iVoc was 30 cm/s and 630 mV respectively.•LBC solar cell with photolithographic contacts exhibits Voc of 647 mV and η of 19.3%.•The laser fired cell exhibits Voc of 637 mV, and efficiency of 19.0%.

This paper focuses on two main challenges: (i) to achieve a low surface recombination velocity and (ii) the quantitative control of the positive charges contained in the rear SiNx by varying the refractive index (n). We adopted a Si-rich SiNx film with a relatively thin thickness to control the fixed charge density (Qf) from 2.74 × 1012 to 1.63 × 1012/cm2 and flat-band voltage (VFB) is shifted from −2.53 to −1.41 V. A rear side recombination velocity (Srear) and implied open circuit voltage (iVoc) was achieved 30 cm/s and 630 mV respectively after forming gas anneal (FGA) treatment. The low temperature processed LBC solar cell fabricated with photolithographic contacts exhibits Voc of 647 mV, and efficiency of 19.3%. The laser fired cell exhibits Voc of 637 mV, and efficiency of 19.0%.