Impact of Copper Intercalation on Thermoelectric Properties in Polyol Method-Prepared Cu_xBi₂Se₃, x = 0, 0.05, 0.10, and 0.15 Nanosheets

Copper-doped single-phase nanosheets (NSs) of rhombohedral Cu x Bi 2 Se 3, x = 0, 0.05, 0.10, and 0.15 with the space group R 3̅ m of crystallite size in the range of 36–43 nm and an average thickness of 41 nm have been synthesized successfully in a modified polyol method using diethylene glycol (DEG) alone. Thermoelectric (TE) properties of these samples have been reported here. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Raman study show that Cu intercalates into the Bi 2 Se 3 lattice. Notably, a large negative Seebeck coefficient with a relatively low electrical resistivity indicates their n-type semiconducting nature with low energy charge filtering in the electrical transport. A 330% enhancement in the TE figure of merit ( ZT ) at 300 K for x = 0.15 compared to that of x = 0 is observed due to the intercalation of Cu between quintuples and energy filtering of carriers at grain boundaries (GBs), showing a good potential of this approach. Therefore, the Cu-intercalation approach to enhance ZT has the potential to pave the way for the future development of more efficient Bi 2 Se 3 -based TE materials that can operate effectively near room temperature.