Development of SnS/In2S3 core-shell nanoparticles for solar cell application

SnS nanoparticles (NPs) were synthesized by a colloidal route at low temperatures and analyzed by several characterization techniques. Whereas transmission electron microscopy (TEM) and atomic force microscopy (AFM) imaging conclusively proved quantum dot sized particles (~4 nm) with a narrow size distribution, Torsional Resonance-Tunneling AFM and Peak Force AFM proved the conductive nature of the particles. The chemical composition, studied by energy dispersive X-ray spectroscopy (EDX) showed the ratio S:Sn of 1:1, confirming that the semiconductor is SnS and not any other compound. To passivate the QD surface and protect it from reaction to ambient, core-shell structures were made. The SnS nanoparticles (NPs) were immersed in a CBD bath for deposition of In₂S₃ layers. The formed core/shell SnS/In₂S₃ nanoparticles were separated by centrifugation and washed with ethanol. The structure of the core-shell SnS/In₂S₃ NPs has been studied by High Resolution TEM which showed the lattice fringes of the SnS core, surrounded by amorphous matrix, tentatively attributed to In₂S₃. The EDX confirms the presence of the elements expected. The absorption spectra of SnS/In₂S₃ nanoparticles with increasing time of CBD In₂S₃ clearly showed increasing band gap, attributed to thicker In₂S₃ shell. Research on SnS QDs embedded in CIS solar cells is in progress.