Influence of band gap of p-type hydrogenated nanocrystalline silicon layer on the short-circuit current density in thin-film silicon solar cells

The impact of the optical band gap (E_g) of a p-type hydrogenated nanocrystalline silicon layer on the short-circuit current density (J_sc) of a thin-film silicon solar cell is assessed. We have found that the J_sc reaches maximum when the E_g reaches optimum. The reason for the J_sc on E_g needs to be clarified. Our results exhibit that maximum J_sc is the balance between dark current and photocurrent. We show here that this dark current results from the density of defects in the p-layer and the barrier at the interface between p-and i-layers. An optimum cell can be designed by optimizing the p-layer via reducing the density of defects in the p-layer and the barrier at the p/i interface. Finally, a 6.6% increase in J_sc was obtained at optimum E_g for n-i-p solar cells.