Formation, structure and photoelectrical properties of poly-p-xylylene–PbS semiconductor nanocomposite films

Poly-p-xylylene–PbS nanocomposite films were synthesized by simultaneous low-temperature cocondensation of p-xylylene and PbS vapors. Structure of highly dispersed poly-p-xylylene–PbS composites was studied by UV–Vis spectroscopy and by X-ray method. It was established that PbS forms the nanocrystals of 4 nm highly dispersed in amorphous regions of poly-p-xylylene (PPX). It has been shown that the arrangement of nanocrystals in composite films is determined by poly-p-xylylene supramolecular structure: PbS nanocrystals are localized in the poly-p-xylylene amorphous regions characterized by high free volume. Dark conductivity decreases at long-term storage of film that probably results from the diffusion and rearrangement of PbS clusters in amorphous regions. Synthesized PbS composites reveal the essential photoconductive effect. Low energy of excited light, the temperature and voltage dependence of observed photoconductivity lead to the conclusion that the conductivity is determined by the photostimulated tunnel electron transfer between semiconductor–nanocrystals.