A flat panel detector, comprising a substrate and a plurality of photodiodes on the substrate, wherein the flat panel detector further comprises a signal line connected to a photodiode of the plurality of photodiodes to provide a bias voltage to the photodiode, and a second transparent conductive layer on a side of the photodiode of the plurality of photodiodes close to the signal line, an orthographic projection of the second transparent conductive layer on the substrate is located within an orthographic projection of the photodiode on the substrate, wherein the flat panel detector further comprises a plurality of gate scanning lines, a plurality of data lines and a thin film transistor on the substrate, the thin film transistor is electrically connected to a gate scanning line of the plurality of gate scanning line and a data line of the plurality of data line and the photodiode, respectively, characterized in that, the flat panel detector further comprises a first transparent conductive layer arranged on a side of the plurality of photodiodes away from the substrate, an orthographic projection of the first transparent conductive layer on the substrate at least partially overlaps an orthographic projection of each photodiode of the plurality of photodiodes on the substrate, wherein the signal line is disposed between the first transparent conductive layer and the photodiode, the first transparent conductive layer is in direct contact with the signal line, wherein the first transparent conductive layer comprises a plurality of conductive patterns, the plurality of conductive patterns are connected together by conductive connection sections, or the first transparent conductive layer comprises an opening corresponding to the thin film transistor, an orthographic projection of the opening on the substrate overlaps an orthographic projection of the thin film transistor on the substrate. wherein the flat panel detector further comprises a signal line connected to a photodiode of the plurality of photodiodes to provide a bias voltage to the photodiode, and a second transparent conductive layer on a side of the photodiode of the plurality of photodiodes close to the signal line, an orthographic projection of the second transparent conductive layer on the substrate is located within an orthographic projection of the photodiode on the substrate, wherein the flat panel detector further comprises a plurality of gate scanning lines, a plurality of data lines and a thin film transistor on the substrate, the thin film transistor is electrically connected to a gate scanning line of the plurality of gate scanning line and a data line of the plurality of data line and the photodiode, respectively, characterized in that, the flat panel detector further comprises a first transparent conductive layer arranged on a side of the plurality of photodiodes away from the substrate, an orthographic projection of the first transparent conductive layer on the substrate at least partially overlaps an orthographic projection of each photodiode of the plurality of photodiodes on the substrate, wherein the signal line is disposed between the first transparent conductive layer and the photodiode, the first transparent conductive layer is in direct contact with the signal line, wherein the first transparent conductive layer comprises a plurality of conductive patterns, the plurality of conductive patterns are connected together by conductive connection sections, or the first transparent conductive layer comprises an opening corresponding to the thin film transistor, an orthographic projection of the opening on the substrate overlaps an orthographic projection of the thin film transistor on the substrate.