Low-temperature one-pot synthesis of nickel and iodine-doped photosensitive thin films of lead(II) sulfide

The efficiency of combined donor–acceptor doping of thin lead sulfide films with nickel and iodine ions using the one-pot approach for obtaining photosensitive lead sulfide layers PbS(I, Ni) was shown. Chemical bath deposition of the lead sulfide films from an ammonia-citrate reaction mixture with a combined additive of NH₄I and NiCl₂ was carried. The conditions for the films deposition were preliminarily determined by analyzing ionic equilibria in an ammonia-citrate reaction mixture. Composition, morphology and structure of the synthesized layers were studied using scanning electron microscopy, energy-dispersive elemental analysis and X-ray diffraction. Non-monotonic changes of the content of the main elements Pb, S, I, and Ni in the lead sulfide films, lattice parameter, crystallographic orientation of grains, microstresses and coherent scattering regions, as well as band gap depending on the concentration of NiCl₂ in the reaction bath with extreme values near 1–2 mM NiCl₂ were revealed. The analysis of Raman and Fourier-transform infrared transmission spectra showed the formation of diiodine pentoxide I₂O₅, iodate ion IO³⁻, and nickel oxide NiO in the PbS(I, Ni) films in addition to the PbI₂ phase. A 1.8-fold increase in voltage sensitivity and a 7.5-fold increase in detectivity of the PbS(I, Ni) film deposited in the presence of 0.15 M NH₄I and 2 mM NiCl₂ compared to the film deposited in the presence of only 0.15 M NH₄I were found. A significant increase in voltage sensitivity and detectivity of the PbS(I, Ni) films is caused by a synergistic effect of the doping additives with the formation of photoactive phases of lead iodide and iodine and nickel oxides.