A light conversion device includes a light-emitting unit, a photoelectric conversion unit, and an electroconductive bonding layer. Each of the light-emitting unit and the photoelectric conversion unit includes a first-type region and a second-type region opposite to the first-type region. The electroconductive bonding layer is disposed between the light-emitting unit and the photoelectric conversion unit for connecting the photoelectric conversion unit with the light-emitting unit. When the photoelectric conversion device is operated to receive a bias and an external light, the light-emitting unit generates a modulated light different from the external light in frequency.