Merged organic-silicon heterojunction devices require the passivation of dangling bonds at the silicon surface, preferably with a low-temperature process. In this paper, we demonstrate the high-quality passivation of the silicon (100)surface using an organic molecule (9,10-phenanthrenequinone, PQ). PQ reacts with the dangling bonds, thus providing a bridge between organic semiconductors and silicon. We measure low recombination velocities (~150 cm/s) at the PQ-silicon interface. Metal/organic-insulator/silicon capacitors and transistors prove that at PQ-silicon interface, the Fermi level can be modulated. The formation of an inversion layer with electron mobility of 600 cm2/Vs further demonstrates the passivation quality of PQ.