A substrate for a digital X-ray detector, the substrate comprising: a base substrate comprising an active region including a plurality of pixel regions; a plurality of gate lines arranged in a first direction on the active region of the base substrate; a plurality of data lines arranged in a second direction to intersect with the first direction on the active region of the base substrate; a plurality of bias lines arranged in the first direction or the second direction on the active region of the base substrate; a plurality of thin film transistors (Tr) corresponding each to one of the plurality of pixel regions, each of the thin film transistors arranged at an intersection between a respective gate line of the plurality of gate lines and a respective data line of the plurality of data lines, and each of the thin film transistors comprising an active layer, a gate insulating layer on a portion of the active layer, a gate electrode on the gate insulating layer, an interlayer dielectric layer arranged on the active layer and the gate electrode, and source and drain electrodes on the interlayer dielectric layer; a first passivation layer arranged on the plurality of thin film transistors (Tr); a first hydrogen blocking layer arranged on the first passivation layer; a plurality of photodiodes arranged on the first passivation layer and corresponding each to one of the plurality of pixel regions, each of the photodiodes electrically connected to a respective thin film transistor of the plurality of thin film transistors; a second passivation layer arranged on the plurality of photodiodes and on the first hydrogen blocking layer; characterized in that the base substrate further comprises a pad region outside the active region and a pad electrode on the pad region of the base substrate, the pad electrode comprising a layer (220p, 640p) formed of the same material and formed through the same process as the first hydrogen blocking layer, in that the first hydrogen blocking layer is arranged on the first passivation layer in an island form in a transistor region which corresponds to the active layer of each of the thin film transistors, and in that each of the photodiodes is spaced from the first hydrogen blocking layer. a base substrate comprising an active region including a plurality of pixel regions; a plurality of gate lines arranged in a first direction on the active region of the base substrate; a plurality of data lines arranged in a second direction to intersect with the first direction on the active region of the base substrate; a plurality of bias lines arranged in the first direction or the second direction on the active region of the base substrate; a plurality of thin film transistors (Tr) corresponding each to one of the plurality of pixel regions, each of the thin film transistors arranged at an intersection between a respective gate line of the plurality of gate lines and a respective data line of the plurality of data lines, and each of the thin film transistors comprising an active layer, a gate insulating layer on a portion of the active layer, a gate electrode on the gate insulating layer, an interlayer dielectric layer arranged on the active layer and the gate electrode, and source and drain electrodes on the interlayer dielectric layer; a first passivation layer arranged on the plurality of thin film transistors (Tr); a first hydrogen blocking layer arranged on the first passivation layer; a plurality of photodiodes arranged on the first passivation layer and corresponding each to one of the plurality of pixel regions, each of the photodiodes electrically connected to a respective thin film transistor of the plurality of thin film transistors; a second passivation layer arranged on the plurality of photodiodes and on the first hydrogen blocking layer; characterized in that the base substrate further comprises a pad region outside the active region and a pad electrode on the pad region of the base substrate, the pad electrode comprising a layer (220p, 640p) formed of the same material and formed through the same process as the first hydrogen blocking layer, in that the first hydrogen blocking layer is arranged on the first passivation layer in an island form in a transistor region which corresponds to the active layer of each of the thin film transistors, and in that each of the photodiodes is spaced from the first hydrogen blocking layer.