The present disclosure relates to a light detector. The light detector includes a first electrode, a second electrode, a current detector, a power source and a nano-heterostructure. The nano-heterostructure is electrically coupled with the first electrode and the second electrode. The nano-heterostructure includes a first carbon nanotube, a second carbon nanotube and a semiconductor layer. The semiconductor layer includes a first surface and a second surface opposite to the first surface. The first carbon nanotube is located on the first surface, the second carbon nanotube is located on the second surface.