The photoelectronic properties of organic semiconductor-silicon heterostructures (such as PTCDA-Si, CuPc-Si, and OPV-Si) are investigated. The I-V characteristics, as well as the spectral dependences of photoconductivity and photoinduced potential, are measured. Photosensitivity is observed in the absorption bands of both silicon and the organic films. A maximum potential (up to 0.25 V) is observed for the PTCDA-Si heterojunctions. In the OPV-Si heterojunction, the photoinduced potential changes sign under illumination at different wavelengths in the optical range.