Enhanced thermoelectric performance of flexible PEDOT:PSS/PEG matrices incorporating hollow Ag@Ag₂Se core-shell...

Flexible thermoelectric (TE) materials that can efficiently convert low-grade heat into electricity have received increasing attention for wearable and portable energy-harvesting systems. In this study, hollow Ag@Ag₂Se core-shell fillers were synthesized via a NaCl-templated method and incorporated into a PEDOT:PSS/PEG hybrid matrix to construct flexible TE composites. The hollow structure effectively reduced thermal transport through phonon scattering, while the metallic Ag core and semiconducting Ag₂Se shell provided continuous electron pathways and interfacial energy filtering. The addition of PEG improved interfacial compatibility and introduced thermal buffering behavior within the polymer network. As the filler content increased, both electrical conductivity and Seebeck coefficient were enhanced due to synergistic carrier transport between the hybrid phases. For the optimized composite containing 10 wt% hollow Ag@Ag₂Se, the maximum electrical conductivity of 41 913 S m^-1 was achieved at 375 K, whereas the highest Seebeck coefficient of -151.5 μV K^-1 and the maximum power factor of 876 μW m^-1 K^-2 were obtained at 300 K. Despite the increased electrical performance, the overall thermal conductivity remained as low as 0.4 W m^-1 K^-1, resulting in a peak figure of merit (ZT) of 0.62. Moreover, the flexible device exhibited stable and reproducible output power of 3.8 μW at a temperature difference of 50 K. These results demonstrate that the combination of hollow Ag@Ag₂Se fillers and the PEDOT:PSS/PEG matrix provides an effective strategy for realizing high-performance, flexible thermoelectric materials suitable for low-grade waste heat recovery and wearable energy applications.