A Review of the Synthesis, Properties, and Applications of Bulk and Two-Dimensional Tin(II) Sulfide (SnS)

Tin(II) sulfide (SnS) is an attractive semiconductor for solar energy conversion in thin film devices due to its bandgap of around 1.3 eV in its orthorhombic polymorph, and a band gap energy of 1.5–1.7 eV for the cubic polymorph—both of which are commensurate with efficient light harvesting, combined with a high absorption coefficient (10−4 cm−1) across the NIR–visible region of the electromagnetic spectrum, leading to theoretical power conversion efficiencies >30%. The high natural abundance and a relative lack of toxicity of its constituent elements means that such devices could potentially be inexpensive, sustainable, and accessible to most nations. SnS exists in its orthorhombic form as a layer structure similar to black phosphorus; therefore, the bandgap energy can be tuned by thinning the material to nanoscale dimensions. These and other properties enable SnS applications in optoelectronic devices (photovoltaics, photodetectors), lithium- and sodium-ion batteries, and sensors among others with a significant potential for a variety of future applications. The synthetic routes, structural, optical and electronic properties as well as their applications (in particular photonic applications and energy storage) of bulk and 2D tin(II) sulfide are reviewed herein.