Interfacial energy filtering and phonon scattering enable thermoelectric enhancement in Ag2Se/silicate aerogel composites

The thermoelectric (TE) performance of narrow-gap semiconductors near room temperature is fundamentally limited by the coupling of carrier and phonon transport. Here, we demonstrate that trace incorporation of silicate aerogel into β-Ag2Se effectively decouples these processes via interfacial band modulation. The amorphous, electrically insulating aerogel forms nanoscale boundaries that introduce energy barriers at Ag2Se/silicate (nominally Ag2Se/SiOx) interfaces, as evidenced by a 0.4 eV work function increase from ultraviolet photoelectron spectroscopy. These barriers selectively filter low-energy carriers, enhancing the Seebeck coefficient, while simultaneously increasing phonon scattering to suppress lattice thermal conductivity. The optimized composite achieves a peak ZT of ∼1.10 at 343 K—representing a ∼36% improvement over pristine Ag2Se. The performance peaks at 0.3 wt. % silicate aerogel, beyond which the power factor (PF) declines, emphasizing the importance of precise interface engineering. This study establishes interfacial band modulation via additive design as a scalable route to enhance thermoelectric properties of room-temperature materials.