Revisiting Metal Sulfide Semiconductors: A Solution-Based General Protocol for Thin Film Formation, Hall Effect Measurement, and Application Prospects

Nanostructured thin films of metal sulfides (MS) are highly desirable materials for various optoelectronic device applications. However, a general low‐temperature protocol that describes deposition of varieties of MS structures, especially in their film form is still not available in literatures. Here, a simple and highly effective general solution‐based deposition protocol for highly crystalline and well‐defined nanostructured MS thin films from ethanol on variety of conducting and non‐conducting substrates is presented. The films display remarkable electronic properties such as high carrier mobility and high conductivity. When NiS thin film deposited on a flexible polyethylene terephthalate (PET) substrate is used as a fluorine doped tin oxide (FTO)‐free counter electrode in dye‐sensitized solar cells, it exhibits a solar‐to‐electric power conversion efficiency of 9.27 ± 0.26% with the highest conversion efficiency as high as 9.50% (vs 8.97 ± 0.07% exhibited by Pt‐electrode). In addition, the NiS film deposited on a Ti‐foil has demonstrated an outstanding catalytic activity for the hydrogen and oxygen evolution reactions from water. A solution‐based general protocol for the deposition of large varieties of metal sulfide thin films from an ethanol bath on a variety of conducting and non‐conducting substrates is presented. As a proof‐of‐concept for application, a NiS film is investigated as an example, and it is demonstrated to be an outstanding electrocatalytic counter electrode for triiodide reduction in dye‐sensitized solar cells. It also exhibits potentially good electrocatalyst activity for the hydrogen evolution reaction and oxygen evolution reaction from water.