Phosphorous-Doped Silicon Carbide as Front-Side Full-Area Passivating Contact for Double-Side Contacted c-Si Solar Cells

We present an electron selective passivating contact based on a tunneling SiO. capped with a phosphorous doped silicon carbide and prepared with a high-temperature thermal anneal. We investigate in detail the effects of the preparation conditions of the SiC.(n) (i.e., gas flow precursor and annealing temperature) on the interface recombination rate, dopant in-diffusion, and optical properties using test structures and solar cells. On test structures, our investigation reveals that the samples annealed at temperatures of 800-850 °C exhibit an increased surface passivation toward higher gas flow ratio (r = CH
₄
/(SiH
₄
+ CH
₄
)). On textured and planar samples, we obtained best implied open-circuit voltages (i-V
_OC
) of 737 and 746 mV, respectively, with corresponding dark saturation current densities (J
₀
) of ~8 and ~4 fA/cm
²
. The SiC(n) layers with different r values were applied on the textured front side of p-type c-Si solar cells in combination with a borondoped SiC
_∞
(p) as rear hole selective passivating contact. Our cell results show a tradeoff between V
_OC
and short-circuit current density (J
_SC
) dictated by the C-content in the front-side SiC
_∞
(n). On p-type wafers, best V
_OC
= 706 mV, FF = 80.2%, and J
_SC
= 38.0 mA/cm
²
with a final conversion efficiency of 21.5% are demonstrated for 2 × 2 cm2 screen-printed cells, with a simple and patterning-free process based on plasma depositions and one annealing step 800 °C <; T <; 850 °C for the formation of both passivating contacts.