Phosphorous-Doped Silicon Carbide as Front-Side Full-Area Passivating Contact for Double-Side Contacted c-Si Solar Cells
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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 and 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 8 (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 8 (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.
IEEE Journal of Photovoltaics, 9 (2) pp. 346-354, March 2019.