Lead chalcogenide thin films have found their way in a variety of applications over the last three decades. IRdetectors based on these materials, for instance, are commercially used in microelectronics, medicine and for military applications. This work is concerned with the effect of the nanostructure on the photoelectric properties of n-type In-doped PbTe thin films. Nanostructured thin films were prepared by varying the rate of nucleation as a function of the nature and temperature of the substrates. The broken bonds at the grain boundaries generate acceptor states in n-type films, capture electrons from the interior of the grains and give rise to p-type inversion layers between adjacent grains. A model, based on the assumption the current is exclusively due to the motion of holes in the inversion channels along grain boundaries is proposed to explain temperature dependences of photoelectric properties. It was demonstrated such structure is optimal for maximizing their photoconductivity due the separation of electron-hole pairs on grain boundaries and consequently increasing the carrier life time. This approach allows designing IR-detectors based on nanocrystalline PbTe films with high sensitivity at wavelength up to 4-5 μm that do not require cryogenic cooling.