Synergistic effects lead to high thermoelectric performance of iodine doped pseudo-binary layered GeSb2Te4

Pseudo-binary layered compound ⅣVI-V 2 VI 3 families show great promise for application in thermoelectrics. Herein, through introducing iodine in GeSb 2 Te 4 , several synergistic effects come into being and contribute to outstanding thermoelectric performance. The I Te donor-like defects suppress the hole carrier concentration from 5.72 × 10 20 cm −3 to 2.80 × 10 20 cm −3 . First-principles calculations reveal that iodine doping increases the band gap from 0.253 eV to 0.302 eV and contributes to valence band convergence. Seebeck coefficient value reaches up to 135.7 μV/K at 773 K, and the power factor values are entirely boosted in the whole temperature region, reaching a maximum value of 12.4 μW⸱cm −1 ⸱K −2 in GeSb 2 Te 3.96 I 0.04 . Moreover, iodine doping simultaneously reduces the lattice and electronic thermal conductivity, leading to the greatly reduced total thermal conductivity from 2.89 W⸱m −1 ⸱K −1 in pristine sample to 0.89 W⸱m −1 ⸱K −1 in GeSb 2 Te 3.84 I 0.16 at 323 K. Finally, a maximum zT ∼1.12 at 773 K and an average zT ∼0.62 over 323–773 K are achieved in GeSb 2 Te 3.88 I 0.12 . This work puts forward an effective strategy to synergistically optimize phonon and carrier transport properties of pseudo-binary compounds through halogen doping, which may be effective in other similar material systems. • Synergistic effects Iodine doped GST suppresses carrier concentration, achieves band convergence and enhances band gap. • Anisotropy Orientation enhancement benefits the thermoelectrics. • High thermoelectric performance A maximum zT ∼1.12 at 773 K and an average zT ∼0.62 at 323–773 K are achieved.