The uncontrolled dendrite induces sodium metal inferior electrochemical performance and even severe safety issue, dragging the metallic sodium anode out of practical application. Herein, an artificial reduced graphene oxide/carbon nanotube...

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Cu3SbS4-based materials composed of nontoxic, low-cost, and earth-abundant elements potentially exhibit favorable thermoelectric performance. However, some key transport parameters and thermal stability have not been reported. In this work, the effects of Bi and Sn co-doping on thermoelectric properties and the thermal stability of Cu3SbS4 were studied by experiment and theoretical validation. Bi and Sn doping can effectively tune the electrical properties and the electronic band structure. The Bi and Sn doping leads to an increased carrier concentration from 6.4 × 1017 to 7.4 × 1020 cm–3 and a decreased optical band gap from 0.85 to 0.73 eV. The effective mass was increased from ∼3.0 me for Bi-doped samples to ∼4.0 me for Bi and Sn co-doped samples. An enhanced power factor of 1398 μW m–1 K–2 at 623 K was obtained for Cu3Sb1–x–y Bi x Sn y S4 (x = 0.06, y = 0.09). The measurements of elastic properties exhibited a large Grüneisen parameter (γ ∼2) for Cu3SbS4-based materials. Finally, a maximum zT of 0.76 ± 0.02 at 623 K was achieved for Cu3Sb1–x–y Bi x Sn y S4 (x = 0.06, y = 0.05) sample. In addition, Cu3SbS4 materials possess excellent thermal stability after thermal treatment in vacuum at 573 K for totally 500 h and dozens of heating–cooling thermal cycles (300–623–300 K). It indicates that Cu3SbS4 is a robust alternative for Te-free thermoelectric materials at an intermediate temperature range. This work provides feasible guidance to survey the thermal stability of chalcogenides.

Carbon nanodots (CDs) have emerged as an alternative option for traditional nanocrystals due to their excellent optical properties and low toxicity. Nevertheless, high emission efficiency is a long-lasting pursuit for CDs. Herein, CDs with near-unity emission efficiency are prepared via atomic condensation of doped pyrrolic nitrogen, which can highly localize the excited states thus lead to the formation of bound excitons and the symmetry break of the 𝝅-electron conjugation. The short radiative lifetimes (<8 ns) and diffusion lengths (<50 nm) of the CDs imply that excitons can be efficiently localized by radiative recombination centers for a defect-insensitive emission of CDs. By incorporating the CDs into polystyrene, flexible light-converting films with a high solid-state quantum efficiency of 84% and good resistance to water, heating, and UV light are obtained. With the CD-polymer films as light conversion layers, CD-based white light-emitting diodes (WLEDs) with a luminous efficiency of 140 lm W −1 and a flat-panel illumination system with lighting sizes of more than 100 cm 2 are achieved, matching state-of-the-art nanocrystal-based LEDs. These results pave the way toward carbon-based luminescent materials for solid-state lighting technology.