The argyrodite compounds (A
m/m+ (12− n )
B n + X
2− 6
(A m + = Li + , Cu + , and Ag+; B n + = Ga 3+ , Si 4+ , Ge 4+ , Sn 4+ , P 5+ , and As 5+ ; and X 2− = S 2− , Se 2− , or Te 2− )) have attracted great attention as excellent thermoelectric (TE) materials due to their extremely low lattice thermal conductivity Among them, Ag 8 SnSe 6 -based TE materials have high potential for TE applications. However, the pristine Ag 8 SnSe 6 materials have low carrier concentration (< 10 17 cm −3 ), resulting in low power factors. In this study, a hydrothermal method was used to synthesize Ag 8 SnSe 6 with high purity, and the introduction of SnBr 2 into the pristine Ag 8 SnSe 6 powders has been used to simultaneously increase the power factor and decrease the thermal conductivity ( κ ). On the one hand, a portion of the Br − ions acted as electrons to increase the carrier concentration, increasing the power factor to a value of ∼698 µW·m −1 ·K −2 at 736 K. On the other hand, some of the dislocations and nanoprecipitates (SnBr 2 ) were generated, resulting in a decrease of κ 1 (−0.13 W·m −1 ·K −1 ) at 578 K. As a result, the zT value reaches ∼1.42 at 735 K for the sample Ag 8 Sn 1.03 Se 5.94 Br 0.06 , nearly 30% enhancement in contrast with that of the pristine sample (−1.09). The strategy of synergistic manipulation of carrier concentration and microstructure by introducing halogen compounds could be applied to the argyrodite compounds to improve the TE properties.
Yaobin Xu,Mengmeng Yu,Yu Li,Tiantian Deng,Yajing Feng,Yang Huang,Chao Yu,Chengchun Tang,Jing Lin
Blue-emitting CsPbX 3 (X = Cl, Br, I) nanocrystals (NCs) have potential applications in white light illumination and full-color luminescent displays. However, current methods for synthesizing blue-emitting CsPbX 3 NCs face challenges in poor controllability, low photoluminescence quantum yields (PLQYs), and the harmful effects of short-wavelength blue light. In this work, we report on a SnBr 2 -mediated solvothermal method for the controllable synthesis of blue-emitting CsPbBr 3 nanoplates (NPLs) that exhibit high optical purity within the harmless blue light range. The pioneering use of SnBr 2 as a mediator in solvothermal reactions plays a crucial role in the controllable synthesis process. By increasing the amount of SnBr 2 , the as-prepared products gradually transform from CsPbBr 3 NCs to mixed CsPbBr 3 /Cs 4 PbBr 6 NCs, and finally to CsPbBr 3 NPLs. By further adjusting the solvothermal reaction conditions, CsPbBr 3 NPLs with controlled thickness (2.34–3.53 nm), regulated blue-light emission (459.4–466.6 nm) and a high PLQY up to 63.17% can be obtained. This study provides a feasible method for the controllable synthesis of perovskite NPLs and opens up new possibilities for the application of perovskite blue light-emitting devices.
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