Synergistic Regulation of Phonon and Electronic Properties to Improve the Thermoelectric Performance of Chalcogenide CuIn_1−xGa_xTe₂:yInTe (x = 0–0.3) with In Situ Formed Nanoscale Phase InTe

Most ternary Cu‐In‐Te chalcogenides have large bandgaps and high Seebeck coefficients, hence they have received much attention in the thermoelectric (TE) community. However, it is still challenging to reduce their thermal conductivities while sustaining their electrical properties; therefore, much work needs to be done. The phonon and electronic properties in ternary CuInTe2‐based chalcogenides CuIn1−xGaxTe2:yInTe (x = 0–0.3) with in situ formed nanoscale phase InTe precipitated in the grain boundaries is synergistically regulated. This regulation reduces the lattice thermal conductivity by a factor of ≈2 compared to pristine CuInTe2, due to phonon–phonon interaction and point defect scatterings introduced in the main phase at high temperatures for samples at x ≤ 0.2, combined with the phonon blocking effect from InTe at low and middle temperatures. At the same time, the power factor enhances by 73%. As a result, the TE performance improves significantly with a peak figure of merit value of 1.22 at ≈850 K