The role of buffer layer between TCO and p-layer in improving series resistance and carrier recombination of a-Si:H solar cells

The properties of the window layer and transparent conducting oxide (TCO)/p interface in silicon based thin-film solar cells are important factors in determining the cell efficiency. As the potential barrier got larger at the interface, the transmission of photo-generated holes were impeded and the recombination of photo-generated electrons diffusing back toward the TCO interface were enhanced leading to a deterioration of the fill factor. In this paper different p-layers were studied. It was found that using p-type hydrogenated amorphous silicon oxide (a-SiO _x:H) layer as the window layer along with a 5 nm buffer layer which reduced the barrier at the fluorine doped tin oxide (SnO ₂:F) TCO/p-layer interface, improved the cell efficiency. a-SiO _x:H was used as the buffer layer. With the buffer layer between TCO and p-type a-SiO _x:H, the potential barrier dropped from 0.506 eV to 0.472 eV. This lowered barrier results in increased short circuit current density (J _sc) and fill factor (FF). With the buffer layer, J _sc increased from 11.9 mA/cm ² to 13.35 mA/cm ² and FF increased from 73.22% to 74.91%.