HIGH EFFICIENCIES ON MC-SI SOLAR CELLS ENABLED BY INDUSTRIAL FIRING THROUGH REAR SIDE PASSIVATING SINX:H

摘要

A current challenge in developing low-cost mc-silicon solar cells is to substitute the aluminum back surface field (BSF) to allow the use of much thinner wafers. To be able to reach higher efficiencies on thin wafers the rear surface passivation, the internal rear side reflection and the cell bowing ask for better rear side properties than those of the now commonly used Al BSF. In this paper we present our first steps toward a solar cell of the future that will overcome these drawbacks. We will demonstrate that silicon nitride (SiN_x) can be implemented in an industrial cell line as a rear surface passivating layer reaching higher efficiencies compared to an Al BSF, and without bowing. The rear contacts can be directly fired though the SiN_x, without the need to open the layer. Efficiencies up to 15.5% were reached on mc-Si wafers with rear surface recombination velocities (S_(eff,rear)) down to 175 cm/s. This low S_(eff,rear) will not be limiting the efficiency up to at least 17% cell efficiency. Moreover, up to these efficiencies the good rear side passivation is not hindered by parasitic shunts (caused by fixed charges in the silicon nitride).