Acid-treated organic–inorganic hybrid thermoelectrics for lightweight and efficient mid-temperature energy harvesting

The thermoelectric properties of a series of organic–inorganic hybrid and ternary composites comprising Tellurium (Te)/Polypyrrole–carbon composite (PPy C), Te/Ethylene glycol (EG)–poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), Te/EG–PEDOT:PSS/PPy-C, and Te combined with acid (hydrochloric acid (HCl), sulfuric acid (H 2 SO 4 ), and nitric acid (HNO 3 )) post-treated PEDOT:PSS at loadings of 20, 50, and 90 wt% were systematically investigated. Among the acids examined, HNO 3 post-treatment reduces electrical resistivity while largely retaining the Seebeck coefficient, thereby increasing the power factor. Increasing the HNO 3 -treated PEDOT:PSS content further suppresses total thermal conductivity, primarily due to the polymer's intrinsically low thermal transport. The optimal p -type performance is obtained in the 90 wt% HNO 3 -treated PEDOT:PSS/Te hybrid composite, achieving a peak zT of 0.16 at 450 K. For the n -type counterpart, the Ag 2 Se/Se (1.5 wt%) composite achieves a maximum zT of 0.9 at 375 K. A 12-pair thermoelectric generator (TEG) integrating these optimized p - and n -type legs produces a maximum output power of 17.4 μW (111 mV, 317 μA) and a power density of 13.7 μW·cm −2 at ΔT = 80 K, with respective p -leg, n -leg, and device efficiencies of 0.58 %, 3.65 %, and 2.68 %. These results demonstrate the potential of acid-engineered organic–inorganic hybrids for efficient mid-temperature thermoelectric applications and pave the way for lightweight and high-performance TEG devices.