Plastic/Ductile Bulk 2D van der Waals Single‐Crystalline SnSe<sub>2</sub> for Flexible Thermoelectrics
Tingting Deng, Zhiqiang Gao, Pengfei Qiu, Tian‐Ran Wei, Jie Xiao, Genshui Wang, Lidong Chen, Xun Shi
Abstract
Abstract The recently discovered ductile/plastic inorganic semiconductors pave a new avenue toward flexible thermoelectrics. However, the power factors of current ductile/plastic inorganic semiconductors are usually low (below 5 µW cm −1 K −2 ) as compared with classic brittle inorganic thermoelectric materials, which greatly limit the electrical output power for flexible thermoelectrics. Here, large plasticity and high power factor in bulk two‐dimensional van der Waals (2D vdW) single‐crystalline SnSe 2 are reported. SnSe 2 crystals exhibit large plastic strains at room temperature and they can be morphed into various shapes without cracking, which is well captured by the inherent large deformability factor. As a semiconductor, the electrical transport properties of SnSe 2 can be readily tuned in a wide range by doping a tiny amount of halogen elements. A high power factor of 10.8 µW cm −1 K −2 at 375 K along the in‐plane direction is achieved in plastic single‐crystalline Br‐doped SnSe 2 , which is the highest value among the reported flexible inorganic and organic thermoelectric materials. Combining the good plasticity, excellent power factors, as well as low‐cost and nontoxic elements, bulk 2D vdW single‐crystalline SnSe 2 shows great promise to achieve high power density for flexible thermoelectrics.