Facile synthesis of copper selenides with different stoichiometric compositions and their thermoelectric performance at a low temperature range.

Copper selenide is widely considered to be a promising candidate for high-performance flexible thermoelectrics; however, most of the reported values of copper selenides are unsatisfactory at a relatively low temperature range. Herein, we utilized some wet chemical methods to synthesize a series of copper selenides. XRD, SEM and TEM characterizations revealed that CuSe, CuSe and Cu Se were prepared successfully and possessed different morphologies and sizes. Based on the analysis of their thermoelectric properties, Cu Se exhibited the highest Seebeck coefficient and lowest thermal conductivity among the three samples owing to its unique crystal structure. After being sintered at 400 °C under N atmosphere, the electrical conductivity of Cu Se enhanced considerable, resulting in a significant improvement of its values from 0.096 to 0.458 at 30 to 150 °C. This result is remarkable for copper selenide-based thermoelectric materials at a relatively low temperature range, indicating its brilliant potential in the field of flexible thermoelectric devices.