The present disclosure discloses a photoelectric detector, a preparation method thereof, a display panel and a display device. The photoelectric detector includes a base, and a thin film transistor (TFT) and a photosensitive PIN device on the base, wherein the PIN device includes an I-type region that does not overlap with an orthographic projection of the TFT on the base; a first etching barrier layer covering a top surface of the I-type region; a first heavily doped region in contact with a side surface on a side, proximate to the TFT, of the I-type region; and a second heavily doped region in contact with a side surface on a side, away from the TFT, of the I-type region, the doping types of the first heavily doped region and the second heavily doped region being different from each other.