High thermoelectric performance in Cu2Se/CDs hybrid materials

By embedding organic compound carbon nanodots (CDs) into the inorganic compound Cu2Se, a series of Cu2Se + x wt% CDs (x = 0, 0.2, 0.4, 0.6, and 0.8) nanopowders are obtained through hydrothermal synthesis and then carried out by hot-pressing. The effects of CDs dispersant on resistivity, Seebeck coefficients, and thermal conductivity are investigated. It is found that the resistivity deteriorates, but the Seebeck coefficient increases greatly due to the energy filtering effect of carbon nanodots in the matrix. Higher Seebeck coefficients also lead to higher power factors compared with the matrix. Importantly, carbon nanodots are well distributed in the matrix without obvious agglomeration, and suppress the recrystallization of Cu2Se. With increasing of the content of CDs, phonon scattering increases due to the newly formed interfaces between CDs dispersant and Cu2Se matrix, which reduces thermal conductivity effectively. Correspondingly, the lowest total thermal conductivity reaches 0.45 W/Km at 973 K when x = 0.8. Because of the relatively high power factor and exceptional low thermal conductivity, the Cu2Se + 0.8 wt% CDs sample presents an excellent ZT value of 1.98. The present work indicates that CDs are novel and effective dispersants, and could be furtherly extended to use in other thermoelectric materials. (C) 2019 Elsevier B.V. All rights reserved.