Low-Dimensional InSe Compounds: From Material Preparations to Device Applications.

Nanostructured InSe compounds have been widely used in electronics, optoelectronics, and thermoelectrics. Recently, the revelation of ferroelectricity in low-dimensional (low-D) InSe has caused a new upsurge of scientific interest in nanostructured InSe and advanced functional devices. The ferroelectric, thermoelectric, and optoelectronic properties of InSe are highly correlated with the crystal structure. In this review, we summarize the crystal structures and electronic band structures of the widely interested members of the InSe compound family. Recent achievements in the preparation of low-D InSe with controlled phases are discussed in detail. General principles for obtaining pure-phased InSe nanostructures are described. The excellent ferroelectric, optoelectronic, and thermoelectric properties having been demonstrated using nanostructured and heterostructured InSe with different phases are also summarized. Progress and challenges on the applications of InSe nanostructures in nonvolatile memories, photodetectors, gas sensors, strain sensors, and photovoltaics are discussed in detail. In the last part of this review, perspectives on the challenges and opportunities in the preparation and applications of InSe materials are presented.