Amorphous non-doped, iodine- and tin-doped Sb2S3 nanoparticles were prepared via the hot-injection method. HRTEM of amorphous undoped and doped samples revealed the formation of spherical nanoparticles of 20–50 nm diameter aggregated into clusters in the size of 100–200 nm. EDX analysis indicated the presence of desired elements in all observed samples. The bandgaps of non-doped and doped samples were determined from the reflectance spectra, and variations of the bandgaps, even small ones, are insufficient indications of doping. These uncertainties are further clarified by investigating crystalline undoped and doped samples in addition to the amorphous ones. XRPD results of the amorphous samples confirmed the amorphous structure, while Le Bail refinements of the crystalline samples show well-defined peaks from only the Sb2S3 phase, indicating a successful doping process. XPS measurements revealed that the phase of the undoped sample is free of impurities and that 3 d peaks of iodine and tin in the doped samples are present. The XPS valence bands shifted towards higher (I) or lower (Sn) binding energies compared to the undoped samples for both amorphous and crystalline samples, which is an additional support that incorporation of dopant ions in the Sb2S3 lattice took place.
