Improvement of optical and conductivity properties of SnS2 via Cr doping for photovoltaic applications

Tin disulfide doped with chromium (Sn1-xCrxS2) powders with different molar ratios (x = 0, 2, 4, 6, and 10 at %) were synthesized using a low-cost hydrothermal technique. The prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), high-resolution transmission electron microscopy (HRTEM), UV-Vis spectroscopy, and electrochemical impedance spectroscopy (EIS). The Sn1-xCrxS2 samples maintained the hexagonal structure with space group (S.G.) P-3m1 from the SnS2 structure, according to XRD and Raman measurements. Cr doping was confirmed by EDS, where Cr partially substituted Sn in the SnS2 structure. SEM images also displayed good homogeneity and smaller particle sizes as Cr doping increased. HRTEM and selected-area electron diffraction (SAED) analysis showed high crystallinity of the synthesized samples. The optical bandgap energy (Eg) of the Cr-doped samples with x = 6% was found to be the lowest among the measured values, and even lower than that of the pure SnS2 sample. The conductivity of the samples was measured through-plane using EIS, and the Sn1-xCrxS2 samples with x = 6% again showed superior conductivity performance within the investigated temperature ranges. These findings further support the potential of Cr-doped SnS2 systems for use as a buffer layer in photovoltaic applications.