Abstract: PbS colloidal quantum dots are widely used in the field of photodetectors due to the excellent characteristics including adjustable band gap, solution processable and high absorption coefficient, etc. However, PbS quantum dot photodetectors based on photodiode structure tend to use different materials for the processing of the N-type layer, and thus leading to a much more complexed device design method and fabrication process, which hinders the application of such photodetectors in planar array imaging chips in the future. To simplify the fabrication process, a PbS quantum dot P-N homojunction photodetector is proposed here, in which the P-type and N-type layer are prepared by only one process. Results show that the PbS quantum dot photodetector has a good linear response to different incident intensity. The responsivity of the device is about 0.11 A/W and the specific detectivity is approximately 3.41 × 10¹¹ Jones at 700 nm under the reverse bias voltage of 0.5 V, which indicate the excellent performance of the detector in weak illumination conditions. It can be concluded that the PbS quantum dot P-N homojunction photodetector proposed here can promote its development in the field of planar array imaging and is great helpful to the development of planar array imaging chip techniques based on colloidal quantum dots.