The photovoltaic effect of a-C: Fe/AlOx/Si based heterostructures prepared by Pulsed Laser Deposition (PLD) and its applications for solar cells were investigated. Thin alumina layer with a thickness of ~2nm was introduced to the interface between carbon and silicon, and the photovoltatic properties, such as open circuit voltage of ~0.33 V and short current density of ~4.5 mA/cm2, were improved dramatically compared with the samples without the insulation alumina layer. This may be related to the improvement of interface quality, where there are lower recombination centers such as defects and traps, which are approved by the C-V measurement. This work may shed light on the carbon/silicon based solar cells.