Band Degeneracy and Liquid-like Dynamics in Intercalated La2O2Te/BiAgSeO Thermoelectrics

Abstract Interlayer modulation of layered oxychalcogenide superlattices provides a strategy to decouple electron–phonon transport for high-performance thermoelectric (TE) materials. Herein, an intercalated oxychalcogenide superlattice (La4Bi2Ag2Se2Te2O6) is theoretically designed by inserting a La2O2Te slab into the BiAgSeO framework to synergistically optimize carrier and phonon transport behaviors and systematically uncover an unprecedented synergy of orbital-driven valence band degeneracy and Ag+ liquid-like ionic dynamics. The La4Bi2Ag2Se2Te2O6 superlattice exhibits a highly anisotropic lattice architecture characterized by strong intralayer covalent bonding and weak interlayer interactions, which simultaneously preserves structural stability and promotes pronounced lattice anharmonicity. Meanwhile, stereochemically active Bi 6s2 lone-pair electrons, four-phonon scattering, and phonon–diffuson conversion drastically suppress the lattice thermal conductivity. This work establishes a dual-regulation intercalation paradigm combining band convergence and liquid-cation dynamics, offering a universal route for designing high-efficiency layered TE materials.