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

Abstract CuFeS2 is an eco-friendly n-type thermoelectric (TE) material but with poor performance. It is worth noting that the bandgap (Eg) reduction can enhance the carrier mobility (μH) which further leads to a higher electrical conductivity (σ) 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 ∼0.45 to 0.39 eV with the increase of Ag dopant content, and the reduced Eg leads to an obviously enhanced μH without carrier concentration decreasing. Due to the elevated μH, a higher PF (0.76 × 10−3 Wm−1K−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.