Proverbially, when light is shone onto a material, it can produce direct current (DC) by converting the energy from the light to electricity by photovoltaic effect. Here we found that when a light (with a wavelength from UV to NIR) illuminated at the silicon based devices with various types of junctions (MS, MIS, PN, PIN, etc.) through rotating chopper, they are also able to produce alternating current (AC). The current energy conversion mechanisms are not able to explain this effect. This is a true effect, not artificial or from the environment, which is verified by superposition rule experiments. The magnitude of the AC signals depends on the light intensity, frequency of the chopper, and the active illumination area. The possible mechanism for the generation of signals might be the shift of the Fermi level of the semiconductor due to the temperature change at the surface caused by absorption of light, resulting a time-varying electric filed. This effect can be utilized as a wireless power source, photo sensor and in communication system, etc., which could be widely used in many fields.