A sensor includes an anode and a cathode, and a near-infrared photoelectric conversion layer between the anode and the cathode. The near-infrared photoelectric conversion layer is configured to absorb light of at least a portion of a near-infrared wavelength spectrum and convert the absorbed light into an electrical signal. The near-infrared photoelectric conversion layer includes a first material having a maximum absorption wavelength in the near-infrared wavelength spectrum and a second material forming a pn junction with the first material and having a wider energy bandgap than an energy bandgap of the first material. The first material is included in the near-infrared photoelectric conversion layer in a smaller amount than the second material.