As energy crisis is aggravated, solar cell, as a common form of the development and utilization of solar energy, has attracted more and more attention all over the world. With solar cells developing towards the direction of high efficiency, thin film, non-toxic and rich raw materials, the pure silicon solar cell could not meet these requirements, so the new material and process are imminently required. This paper deals with the photovoltaic effect of the carbon material based on the silicon heterostructure, and its possible application to solar cells. Co2-C98/Al2O3/Si heterostructure with a 4 nm-thick Al2O3 layer shows the best photovoltaic effect performance with a short-current density of 18.75 mA/cm2, an open-circuit voltage of 0.447 V and a power conversion efficiency of 3.27% with AM1.5 illumination, which is much better than Co2-C98/Si heterostructure without the Al2O3 layer. The effect of Al2O3 layer is attributed to the reduction of the interface defects, the suppression of the surface recombination and the enhancement of barrier height, which are proved by the capacitance-voltage and current-voltage measurements under dark condition. This work may shed light on the carbon/silicon based solar cells.