A multicolor photodetector based on the heterojunction of n-Si(111)/TiO2 nanorod arrays responding to both ultraviolet (UV) and visible light is developed by utilizing interface engineering. The photodetector is fabricated via a consecutive process including chemical etching, magnetron sputtering, hydrothermal growth, and assembling. Under a small reverse bias (from 0 to approximate to-2 V), only the photogenerated electrons in TiO2 are possible to tunnel through the low barrier of Delta E-C, and the device only responses to UV light; as the reverse bias increases, the photogenerated holes in Si also begin to tunnel through the high barrier of. E V. As a result, the device is demonstrated to have the capacity to detect both UV and visible lights, which is useful in the fields of rapid detection and multicolor imaging. It has been also observed that the crystal orientation of Si affects the characteristics of bias-controlled spectral response of the n-Si/TiO2 heterojunctions.