Inducing High Power Factor in Cu₂GeSe₃-Based Bulk Materials via (Bi, Zn)-Co-doping

Abstract

In this work, carrier concentration optimization and effective mass increase of Cu 2 GeSe 3 , which were considered to be a synergetic effect of electrical transport properties, were achieved by the co-doping of Bi and Zn on the Cu site. This effect led to a higher Seebeck coefficient of ∼307.76 μV K −1 at 723 K for the Cu 1.988 Bi 0.01 Zn 0.002 GeSe 3 sample. This effect also resulted in a higher power factor of ∼8.66 μW cm −1 K −2 at 723 K and an average power factor of ∼6.29 μW cm −1 K −2 at the temperature range of 303− 723 K for the Cu 1.988 Bi 0.01 Zn 0.002 GeSe 3 sample, which were ∼135 and ∼196% larger than those of pristine Cu 2 GeSe 3 , respectively, and are among the highest value of the Cu 2 GeSe 3 -based sample. Benefiting from simultaneous optimization of the power factor, the maximum ZT of ∼0.75 for the Cu 1.988 Bi 0.01 Zn 0.002 GeSe 3 sample at 723 K was obtained, which is ∼288% higher than that of Cu 2 GeSe 3 .