Thin multicrystalline silicon solar cells with silicon nitride front and rear surface passivation

State-of-the-art multicrystalline silicon (mc-Si) material with minority carrier diffusion lengths exceeding the wafer thickness is commercially available today. It is expected that the diffusion length to wafer thickness ratio will be increasing further due to improved material quality and due to the trend towards thinner wafers to reduce material costs. In order to fully exploit the material quality, a solar cell process that includes excellent rear surface passivation is needed. In this paper we first discuss loss mechanism due to the bulk resistivity of thin wafers, optical losses and losses due to rear surface recombination. Solar cell results for thin mc-Si solar cells with silicon nitride front and rear surface passivation are presented. Experimental results demonstrate that due to the excellent rear surface passivation of our plasma SiN_x films, the presented solar cell process is capable of improving the solar cell performance with decreasing cell thickness.