A flat organic photodetector has a structured first electrode that forms several sub-electrodes, a second electrode, at least one first organic layer, and a second organic layer. The organic layers are situated between the two electrodes and are structured in conformity with the structuring of the first electrode, so that the two organic layers are subdivided into multiple active regions respectively corresponding to the sub-electrodes of the first electrode. An x-ray detector has such a flat organic photodetector and an x-ray absorbing layer applied thereon.