3D‐Printed Dual‐Doped Ag ₂ Se‐Based Thermoelectric Films With Enhanced Thermal Stability

ABSTRACT

While silver selenide (Ag ₂ Se) is considered a promising n ‐type thermoelectric material, the low throughput of conventional solid‐state processing for selenide‐based systems highlights the need for scalable solution‐based alternatives. However, most solution‐processing approaches require thermal annealing to form high‐quality films, whereas Ag ₂ Se exhibits limited thermal stability (<350°C), posing a nontrivial issue for processing. To address this, we systematically investigate the incorporation of a controlled dual dopant (Sb‐Se) into Ag ₂ Se through a compositionally tuned nano‐ink. Flexible Sb _x AgSe _0.5+y films were fabricated using the direct ink writing (DIW) approach, and the doped films demonstrated enhanced thermal stability. The effect of dopants on microstructure was further studied using neutron diffraction at the VULCAN instrument and elemental analysis using SEM‐EDS. Results demonstrated that elemental doping of Sb and Se leads to stable/enhanced Seebeck coefficients after thermal exposure, in contrast to undoped Ag ₂ Se films with decreased Seebeck due to thermal degradation, where the thermal behavior and possible degradation pathways are evaluated at 200, 400, and 600°C. A wearable thermoelectric generator (TEG) demonstrated a peak power density of ∼60 µW cm ⁻² at 30°C temperature difference. Overall, this study suggests the possibility of printing‐based Ag ₂ Se thermoelectric devices with high‐temperature processability for waste‐heat harvesting and harsh electronic applications.