A sensor includes first and second electrodes, and an infrared photoelectric conversion layer between the first and second electrodes, the infrared photoelectric conversion layer being configured to absorb light in at least a portion of an infrared wavelength spectrum and convert the absorbed light to an electrical signal. The infrared photoelectric conversion layer includes a first material having a maximum absorption wavelength in an infrared wavelength spectrum, a second material forming a pn junction with the first material, and a third material having an energy band gap greater than the energy band gap of the first material by greater than or equal to about 1.0 eV. The first material, the second material, and the third material are different from each other, and each of the first material, the second material, and the third material is a non-polymeric material.