Interstitial Cu-Induced Band Structure and Phonon Transport Regulation for Eco-friendly n-Type SnSe2 Thermoelectric Power Generation

Layered n-type SnSe2 is a promising eco-friendly thermoelectric (TE) material, yet its practical application is constrained by low carrier concentration and the inherent coupling of electronic-thermal transport. Herein, a CuCl annealing strategy is developed to leverage Cu interstitial intercalation for the precise modulation of electronic band structures and phonon dispersions in SnSe2. By synergizing with the Cu-induced formation of SnSe heterojunctions, this approach effectively decouples electron and phonon transport. Consequently, the SnSe2-2 mol% CuCl sample achieves a maximum power factor (PF) of 0.74 mW m–1 K–2 and surpasses pristine SnSe2 by 8-fold. Furthermore, the κL is reduced to 0.53 W m–1 K–1 at 723 K, marking a 31% decrease relative to pristine SnSe2. This translates to a dimensionless figure of merit (zT) of 0.88 at 723 K parallel to the spark plasma sintering direction. Notably, we fabricate the first SnSe2-based single-leg thermoelectric generator (TEG), which delivers an energy conversion efficiency of about 2% under a ΔT of 340.8 K. By effectively decoupling electronic and thermal transport, this work unlocks the full potential of eco-friendly SnSe2, providing a sustainable and high-performance paradigm for green energy harvesting without relying on toxic elements.