Date Published: January 08, 2018
Publisher: John Wiley and Sons Inc.
Author(s): Weiran Shi, Minxuan Gao, Jinping Wei, Jianfeng Gao, Chenwei Fan, Eric Ashalley, Handong Li, Zhiming Wang.
The indirect bandgap semiconductor tin selenide (SnSe) has been a research hotspot in the thermoelectric fields since a ZT (figure of merit) value of 2.6 at 923 K in SnSe single crystals along the b‐axis is reported. SnSe has also been extensively studied in the photovoltaic (PV) application for its extraordinary advantages including excellent optoelectronic properties, absence of toxicity, cheap raw materials, and relative abundance. Moreover, the thermoelectric and optoelectronic properties of SnSe can be regulated by the structural transformation and appropriate doping. Here, the studies in SnSe research, from its evolution to till now, are reviewed. The growth, characterization, and recent developments in SnSe research are discussed. The most popular growth techniques that have been used to prepare SnSe materials are discussed in detail with their recent progress. Important phenomena in the growth of SnSe as well as the problems remaining for future study are discussed. The applications of SnSe in the PV fields, Li‐ion batteries, and other emerging fields are also discussed.
Tin‐based binary chalcogenide compounds Sn—X (X = S, Se, Te) have been explored due to their potential applications in the next generation electronic, optical, optoelectronic, and flexible systems. For instance, tin sulfide (SnS) and tin telluride (SnTe) are promising in the application of solar cells.1, 2 Among the Sn—X materials family, tin sulfide (SnS) and tin selenide (SnSe) are the materials consisting nontoxic and economical earth‐abundant elements, which significantly promote their value in sustainable electronic and photonic systems.3, 4, 5
For preparation of massive single‐crystalline SnSe bulk materials, melt‐growth method is usually employed. In the melt‐growth approach, 99.999% pure constituent elements of tin and selenium are mixed in stoichiometric ratio in a sealed quartz ampoule which is then kept in close vacuum (10−5 Torr). The ampoule is then slowly heated to 875 ± 2 °C and the mixture is left for 20 h after that. It is then shaken several times to homogenize the bulk material.30 However, low‐dimensional SnSe material, which promises superior properties than SnSe bulk crystals in many aspects, cannot be achieved by the bulk growth method. A comprehensive review on the preparation of microcrystals (it is characterized with several µm diameters), thin films, and nanostructures of SnSe by various technologies is given below.
In this section, we first discuss the properties of pure bulk SnSe single crystals and polycrystals. Then, methods to enhance their ZT values will be discussed.
As a newborn thermoelectric material, SnSe needs further study. Meanwhile, SnSe initially got attention by the research community for its wonderful behavior in the field of photoelectricity.
In this work, various methods including solution and vapor deposition methods to synthesize SnSe with different morphologies including thin films, nanoflakes, nanoplates, nanosheets, etc., have been reviewed. In the study of properties, we focused on the thermoelectric and optoelectronic properties of SnSe of different morphologies—i.e., bulk, thin films, and nanostructures, and some factors affecting properties, such as metal‐doping, have also been discussed. Moreover, the SnSe‐based applications in a variety of fields like PV devices, solar cells, and solid‐state batteries have been discussed.
The authors declare no conflict of interest.