Trace Cu–Te Co-regulation Decouples Charge and Phonon Transport in High-Performance n-Type Polycrystalline SnSe

Abstract High-performance n-type SnSe single crystals have been realized through extensive carrier and band-structure engineering, whereas n-type polycrystalline SnSe remains comparatively underdeveloped because native Sn vacancies favor p-type conduction and microstructural disorder further impedes electron transport. Here, we show that the co-incorporation of trace Cu and Te effectively decouples electronic and phonon transport in n-type polycrystalline SnSe. Trace Cu doping produces an acceptor-like perturbation but does not severely deplete the electron concentration; instead, it enhances mobility-related transport while concurrently suppressing lattice thermal conductivity. Subsequent Te alloying compensates for the unfavorable carrier-concentration change induced by Cu, improves high-temperature electrical conductivity, and preserves a large Seebeck coefficient. This cooperative el…