Enhanced Thermoelectric Performance in Flexible Sulfur-Alloyed Ag2Se Thin Films.

Flexible thermoelectric generators can directly convert thermal energy harvested from the human body into electricity. The Ag2Se flexible film, a promising material for wearable thermoelectric generators, normally demonstrates an inferior electrical transport property due to its weakened in-plane mobility. In this study, the in-plane electrical transport properties of flexible Ag2Se films were optimized by alloying with additional sulfur. This optimization is achieved by leveraging the differences in elemental electronegativity and the preferred orientation of the Ag2Se films. The sulfur-alloyed Ag2Se thin film, with a nominal ratio of 3 atom %, can reach a maximum mobility of 1150 cm-2 V-1 s-1 at 300 K. So, the optimized room-temperature power factor increases to 1935 µW m-1 K-2. Furthermore, the Ag2Se film alloyed with 3 atom % sulfur exhibits excellent flexibility even after 1000 bending cycles with a radius of 5 mm, characterized by a relative resistance increment of less than 3%. In addition, the corresponding π-type flexible thermoelectric generator possesses a maximum power density of 51 W m-2 at a temperature difference of 50 K.

High-Selectivity Planar Thermal Emitter with a Stable Temperature over 1400 K for a Thermophotovoltaic System.

A selective thermal emitter with superior thermal stability and perfect selective thermal emission in specific bands can facilitate the lifting of the thermophotovoltaic (TPV) energy conversion efficiency in TPV systems. Scalable planar selective thermal emitters with superior spectral selectivity and robust high-temperature stability are desired to meet the requirements of large-scale deployments of TPV systems. However, stably reradiating the available thermal photons at above 1273 K remains a significant challenge for selective thermal emitters. In this work, we demonstrated a high-selectivity planar thermal emitter based on the composite ceramic of ZrC and Al2O3. The prepared selective thermal emitter provides an emissivity of around 90% above the photon energy (0.6 eV) at 1423 K, a strong emission suppression effect below 0.6 eV, and superior thermal stability up to at least 1423 K. Therefore, the overall spectral efficiency can reach around 53%. Coupled with an InGaAs PV cell, the TPV system based on the selective thermal emitter demonstrates a predicted heat-to-electricity power conversion efficiency of 29.78% at 1423 K due to the matched spectral response of the emitter with the PV cell. Our work opens a new way forward for TPV systems based on planar selective thermal emitters.