A ray detector is disclosed, which includes a ray conversion layer for converting a ray incident on the ray detector into visible light, a photoelectric conversion layer for receiving the visible light and converting it into a charge signal, a pixel array having a plurality of pixels for detecting the charge signal, and a substrate below the photoelectric conversion layer, at least for directly or indirectly carrying the photoelectric conversion layer. The photoelectric conversion layer is made from a two-dimensional semiconductor material. Due to the high carrier mobility of the two-dimensional semiconductor material, it is possible to enable the external signal processing system to detect the charge signal more easily, so that a ray source with low energy can be used for ray detection. Therefore, a ray detector with high sensitivity can be provided, which may reduce the usage cost and be advantageous to saving energy.
