Type conversion of p-SnS to n-SnS using a SnCl4/CH3OH heat treatment

Thin films of tin sulphide were prepared at varying thicknesses with a deposition rate of 2 nm/s using the thermal evaporation method. Some films were then dipped in a solution containing tin (IV) chloride in methanol (SnCl₄/CH₃OH) at varying concentrations and then annealed in air at annealing temperatures ≥ 400^°C and annealing times ≥ 60 min. The effects of the treatments on the structural, optical and electrical properties of the layers were investigated. The structural, optical and electrical properties of the as-deposited layers exhibited a thickness dependent behaviour. It was found that the SnCl₄/CH₃OH heat treatments convert the SnS layers from p-type to n-type in a controllable way. This process could be used to produce SnS homojunction solar cells or to passivate the grain boundaries in p-type SnS layers.