Mass production of low-cost screen-printed bifacial N-type Si solar cells with BBr<inf>3</inf>-diffused front emitter and ion-implanted back surface field

Abstract

Formation of boron (B) emitter and phosphorus back surface field (BSF) is a major challenge in mass production of low-cost and high efficiency n-type Si solar cells. This paper reports on the successful mass production of industrially cost-effective 239cm2 n-type Si solar cells. Conventional BBr3 thermal diffusion formed a heavily B-doped emitter, and the phosphorus BSF was formed by ionimplantation followed an annealing, which simultaneously provides dopant activation and SiO2 growth. For metallization, a conventional screen-printing technique was utilized. This process flow in industrial mass production yielded a median efficiency 20.2% from ∼6,000 cells. The champion cell had an efficiency of 20.73% with a Voc of 638mV, J S c of 39.49mA/cm2, and FF of 82.28%.