Enhanced thermoelectric performance of N-type eco-friendly material Cu1-xAgxFeS2 (x=0-0.14) via bandgap tuning

CuFeS2 is an eco-friendly n-type thermoelectric (TE) material but with poor performance. It is worth noting that the bandgap (E-g) reduction can enhance the carrier mobility (mu H) which further leads to a higher electrical conductivity (sigma) and power factor (PF). Density Functional Theory (DFT) calculation results indicated that Ag dopant in the CuFeS2 compound can narrow down the Eg. Hence, a series of Cu1-xAgxFeS2 (x=0-0.14) alloys were prepared by vacuum melting combined with plasma activated sintering to enhance the TE performance via a bandgap tuning route. It can be found that the Eg is indeed shrinking from similar to 0.45 to 0.39 eV with the increase of Ag dopant content, and the reduced Eg leads to an obviously enhanced mH without carrier concentration decreasing. Due to the elevated mH, a higher PF (0.76 x 10(-3) Wm(-1)K(-2)) can be obtained and a peak ZT value of 0.45 is achieved at 723 K in Cu0.88Ag0.12FeS2 sample. Therefore, the bandgap tuning can be regarded as an effective strategy for enhancing the TE performance of CuFeS2. (C) 2019 Elsevier B.V. All rights reserved.