Junegie Hong

The Study of Silane-Free SiC x N y Film for Crystalline Silicon Solar Cells

We deposited plasma-enhanced chemical vapor deposition silicon carbon nitride (SiC x N y ) antireflection coating and passivation layers using a silane-free process. We used a solid polymer source developed at SiXtron Advanced Materials to eliminate the storage and handling of dangerous pyrophoric silane gas. We used ammonia flow rate as a control for the chemical and optical properties in the silane-free process. As NH 3 flow rate increases, the carbon content, refractive index, extinction coefficient, and surface charge density of the film decrease. At an ammonia flow rate of 3000 sccm, which is similar to the conventional SiN x , the extinction coefficients for the two films were similar. This led to an emitter dark saturation current density (J oe ) of 404 fA/cm 2 for the two films on 45 Ω/□ emitters. However, a stack passivation of SiO 2 /SiC x N y on an 80 Ω/□ emitter resulted in an emitter dark saturation current density of 95 fA/cm 2 , which is enough to provide a good surface passivation for high efficiency solar cells. An energy conversion efficiency of 17.4% was obtained for a 149 cm 2 textured Czochralski screen-printed solar cell with this stack passivation. For a 156 cm 2 nontextured multicrystalline silicon, with only SiC x N y and a 45 Ω/□ emitter, we obtained 14.9% efficiency.

Reduction of light induced degradation (LID) in B-doped Cz-Si solar cells by SiH 4 -free SiC x N y film

Boron doped Czochralski (Cz) silicon solar cells undergo efficiency degradation under illumination. The light induced degradation (LID) is related to the formation of B<inf>s</inf>-O<inf>2i</inf> complexes which act as a strong recombination centers. This paper shows that carbon present inside the SiC<inf>x</inf>N<inf>y</inf> films deposited from polymer solid or liquid source reduce the LID in boron doped Cz solar cells. The in situ grown carbon in the antireflection (AR) films provides a source of additional carbon which gets incorporated into the bulk silicon (Si) during the cell processing. This carbon competes with boron to form a carbon-oxygen related complex and reduces the B<inf>s</inf>-O<inf>2i</inf> concentration and the associated LID compared to conventional SiN<inf>x</inf> coated solar cells. SiC<inf>x</inf>N<inf>y</inf> coated solar cells showed 0.1% loss in absolute efficiency due to LID relative to 0.3% degradation in the counterpart SiNx coated solar cells on 2 Ω-cm boron doped Cz material.