Phase Formation Study of SnS Nanoparticles Synthesized Through PVP Assisted Polyol Method

Abstract

The optimization study on the preparation of single phase of SnS nanoparticles by varying Sn:S source concentration ratio (1:1, 1:6 and 1:12M) through PVP assisted polyol synthesis method is successfully investigated. The single phase formation, crystal structure, surface morphology and optical properties of SnS nanoparticles have been studied using characterization techniques such as confocal Raman spectrometer, SEM, HR-TEM, UV-VIS-NIR spectrophotometer and spectrofluorometer. Confocal Raman as well as selected area electron diffraction analyses confirmed the single phase formation of SnS NPs with orthorhombic crystal structure at 1:12 ratio whereas SnS2 and Sn2S3 phases formed for lower sulphur concentration. Surface morphology reveals the formation of SnS nanorods predominantly, due to the addition of PVP which act as a capping agent. Band gap calculation from tauc plot showed direct band gap of 1.45 eV for single phase SnS with orthorhombic crystal structure, which can be used as an absorber layer in thin film solar cells. The observed shift in the band gap value is discussed in detail with the support of chemical structure analysis. The PL spectra of samples consists of 3 major peaks; the peak at 411 nm (3.03 eV) corresponds to Sn vacancy (VSn), the peak at 435 nm (2.86 eV) corresponds to tin interstitial (ISn) and peak at 459 nm (2.70 eV) corresponds to sulphur vacancy (VS). Whereas the additional peaks observed by decreasing the sulphur concentration to 0.6 and 0.1 M corresponds to the band edge emission of Sn2S3 and SnS2 respectively.