An array substrate, a manufacturing method thereof, and a display device are provided. The array substrate includes a display area and a non-display area. The non-display area includes at least one light sensor each including a light blocking layer on a substrate and for blocking light emitted from a backlight source; an insulating layer on the light blocking layer; a amorphous silicon layer on the insulating layer at a location corresponding to the light blocking layer and for sensing external light; an input electrode and an output electrode on the amorphous silicon layer and not contacting each other. The input electrode and the output electrode both contact the amorphous silicon layer, a part of the amorphous silicon layer between the input electrode and the output electrode forms a conductive channel. The output electrode is connected with a photoelectric detection circuit for inputting drain current generated by the conductive channel into the photoelectric detection circuit.