Of all the different types of infrared radiation photodetectors, only photoresistors based on lead sulfide PbS possess a variety of different methods and technologies of fabrication. This is because the first photoresistors were fabricated before the development of the theory of photoconductivity in monocrystals and, second, because of the failures which developers of photodetectors based on monocrystalline structures had experienced. The high absorption factor (10 4 cm ‐1 ) [1] suggested the use of thin (1‐2 µm) layers, whereas production of monocrystalline layers by an epitaxial method is possible only at high concentrations of the majority carriers (p ≥ 10 17 cm ‐3 ), which led to a decrease in the life of the carriers. Often, such films are considered to be nonphotosensitive, since the life of the carriers becomes less than their flight time to contact. Polycrystalline films that are suitable for the fabrication of photodetectors are one alternative. Methods of producing these types of films are provisionally divided into chemical methods based on reactions between acetic lead Pb(CH 3 COO) 2 , thiocarbamide (NH 2 ) 2 CS, caustic soda, and other reduction-oxidation agents, and physical methods, in which the primary PbS layer is deposited in a vacuum by means of thermal deposition. In most of the technologies employed, the layer is then annealed in a muffle furnace, oxygen (which is an acceptor impurity) then being introduced into the film. In certain cases, a technique of redeposition of layers in a vacuum with one photodetector layer on top of another is used, as a result of which a layer entraps only the limited number of molecules of oxygen necessary for increasing the life of the vacancies. Successes in the development of photodetectors based on polycrystalline films functioning at a frequency of 400‐1000 Hz have made it possible to solve urgent problems. In the transition from monocrystalline to polycrystalline layers, the mobility of the carriers falls 100-fold (with increasing dark resistance), with 1/F α -type noise becoming dominant over