Boron Implanted Junction with In Situ Oxide Passivation and Application to p‐PERT Bifacial Silicon Solar Cell

Abstract

Boron junction and its passivation is an active topic in photovoltaic research due to its importance to passivated emitter and rear totally‐diffused (PERT) bifacial Si solar cell. In this paper, a systematic study on boron‐implanted junction, its passivation and ohmic contact formation, as well as application to p‐PERT bifacial cells has been presented. More specifically, the impact of junction profile and surface passivation on boron junction quality, which can be influenced by implantation and in situ oxidation anneal parameters is studied. Good‐quality boron emitter and metal/p+‐Si ohmic contact are achieved, as demonstrated by emitter saturation current of 5–30 fA cm−2 and specific contact resistance of 3–6 mΩ cm−1. A roadmap for a p‐PERT bifacial cell using fully ion implanted (boron and phosphorus) technology, based on which p‐PERT bifacial cells demonstrats front side efficiency of 20.6% (open circuit voltage of 658 mV), rear side efficiency of ≈17% and bifaciality factor of 0.82–0.87 is also presented. Effective cell efficiency of ≈22% is achieved with a Halm IV‐tester with white transporting belts that enhance reflection about 10% from the cell rear.