lead(ii) selenide Infrared detection

  PbSe is one of the first materials sensitive to the infrared radiation used for military applications. Early research works on the material as infrared detector were carried out during the 1930s and the first useful devices were processed by Germans, Americans and British during and just after World War II. Since then, PbSe has been commonly used as an infrared photodetector in multiple applications, from spectrometers for gas and flame detection to infrared fuzes for artillery ammunition or Passive Infrared Cueing systems (PICs).

  As a sensitive material to the infrared radiation, PbSe has unique and outstanding characteristics: it can detect IR radiation of wavelengths from 1.5 to 5.2 μm (mid-wave infrared window, abbreviated MWIR – in some special conditions it is possible to extend its response beyond 6 μm), it has a high detectivity at room temperature (uncooled performance), and due to its quantum nature, it also presents a very fast response, which makes this material an excellent candidate as detector of low cost high speed infrared imagers. 

  Theory of operation

  PbSe is a photoconductor material. Its detection mechanism is based on a change of conductivity of a polycrystalline thin-film of the active material when photons are incident. These photons are absorbed inside the PbSe micro-crystals causing then the promotion of electrons from the valence band to the conduction band. Even though it has been extensively studied, today the mechanisms responsible of its high detectivity at room temperature are not well understood. What is widely accepted is that the material and the polycrystalline nature of the active thin film play a key role in both the reduction of the Auger mechanism and the reduction of the dark current associated with the presence of multiple intergrain depletion regions and potential barriers inside the polycrystalline thin films.