High Thermoelectric Performance through Crystal Symmetry Enhancement in Triply Doped Diamondoid Compound Cu ₂ SnSe ₃

The presence of high crystallographic symmetry and nanoscale defects are favorable for thermoelectrics. With proper electronic structures, a highly symmetric crystal tends to possess multiple carrier channels promote electrical conductivity without sacrificing Seebeck coefficient. In addition, can effectively scatter acoustic phonons suppress thermal conductivity. Here, it is reported that the triple doping Cu2SnSe3 leads ZT value 1.6 at 823 K Cu1.85Ag0.15(Sn0.88Ga0.1Na0.02)Se3, decent average (ZTave) 0.7 also achieved Cu1.85Ag0.15(Sn0.93Mg0.06Na0.01)Se3 from 475 K. This study reveals: 1) Ag on Cu sites generates numerous point greatly decreases lattice 2) Doping Mg or Ga converts monoclinic into cubic structure. enhancing an increase in effective mass 0.8 me 2.6 (me, free electron mass) power factor 4.3 µW cm−1 K−2 11.6 K−2. 3) Na creates dense dislocation arrays nanoprecipitates, which strengthens phonon scattering. 4) Pair distribution function analysis shows localized breakdown Cu1.85Ag0.15(Sn0.88Ga0.1Na0.02)Se3. work provides standpoint design promising thermoelectric materials by synergistically manipulating defects.