Material Properties of Nanocrystalline Silicon Carbide for Transparent Passivating Contact Solar Cells

Abstract

Due to its high transparency, silicon carbide can replace amorphous silicon as a front contact material in crystalline silicon solar cells. Herein, first a look at doping in nc-SiC:H with different deposition techniques is taken. Then, the influence of various deposition conditions for hot wire chemical vapor deposition-prepared nc-SiC:H is investigated. Both the electrical conductivity and the optical bandgap increase simultaneously for a multitude of deposition parameters. Combining a high filament temperature of the catalytic filament, a high hydrogen dilution of the precursor gas and an overall low total gas flow, conductivities of 0.38 S cm−1 in combination with an optical bandgap of 3.2 eV can be achieved. In the last section, a closer look into the dependencies of the layer thicknesses of the two different nc-SiC:H layers applied in solar cells on the cell performance is taken. While the layer with conducting properties only has minor influences on cell properties, a trade-off between passivation and fill factor is identified for the passivating nc-SiC:H layer. For thicker layers, the passivating nc-SiC:H layer achieves a very high implied open-circuit voltage above 740 mV, but the fill factor starts to degrade due to a very low conductance of the layer.