We present nanocrystalline PbS, which was prepared using a solvothermal method followed by spark plasma sintering, as a promising thermoelectric material. The effects of grains with different length scales on phonon scattering of PbS samples, and therefore on the thermal conductivity of these samples, were studied using transmission electron microscopy and theoretical calculations. We found that a high density of nanoscale grain boundaries dramatically lowered the thermal conductivity by effectively scattering long-wavelength phonons. The thermal conductivity at room temperature was reduced from 2.5 W m À1 K À1 for ingot-PbS (grain size 4200 lm) to 2.3 W m À1 K À1 for micro-PbS (grain size 40.4 lm); remarkably, thermal conductivity was reduced to 0.85 W m À1 K À1 for nano-PbS (grain size B30 nm). Considering the full phonon spectrum of the material, a theoretical model based on a combination of first-principles calculations and semiempirical phonon scattering rates was proposed to explain this effective enhancement. The results show that the high density of nanoscale grains could cause effective phonon scattering of almost 61%. These findings shed light on developing high-performance thermoelectrics via nanograins at the intermediate temperature range.

In this study, we report novel Au/Cu2O multi-shelled porous heterostructures (MSPHs).

This work takes advantage of a diphenyl-diacetylene-based co-micellar nano-ensemble that can undergo a sequential photocrosslinking to form a corresponding trimeric oligodiacetylene and a dimeric oligodiacetylene.

We numerically calculate the wave function of two-dimensional electron gas (2DEG) for use in 2DEG transport theory and study the electron transport in ZnMgO/ZnO heterostructures. For strongly confined 2DEG, the temperature dependence of the electron mobility is satisfactorily explained using 2DEG transport theory. The interface roughness and ionized impurity scatterings play important roles in the electron transport at low and moderate temperatures. At room temperatures polar optical phonon scattering is the most important scattering mechanism. For heterostructures having two parallel conduction paths in the 2DEG at the ZnMgO/ZnO interface and in the ZnO thick layer, the electron transport is contributed by the two paths. We calculate the mobility for the respective conduction paths, and then combine the two mobility components to fit the experimental data. The theoretical calculations are in good agreement with the experimental data.

In this study, a simple and systematic shapecontrolled synthetic protocol for tailoring nanoscale structures to generate large and monodispersed of three-dimensional (3D) urchin-like Pt−Ni multipods (MPs) and spherical nanoparticles (NPs) is reported, for which the mechanism of production is elaborated in detail. We then demonstrate, for the first time, that the 3D urchin-like Pt−Ni MPs possess good solution processability and substantially enhance both shortcircuit current density (J sc ) and fill factor (FF) and consequently increase the overall power conversion efficiencies (PCEs), because of the combination of multiple scattering processes of incident light, improved conductivity, and facilitating the charge transport in the active layer. PSC fabricated using 5% Pt−Ni MPs embedded in a blend of poly{ [4,8-bis(2-ethyl-hexyl-thiophene-5-yl) [3,4-b]thiophen-4,6-diyl]} (PBDTTT-C-T) and [6,6]-phenyl-C 71 -butyric acid methyl ester (PC 71 BM) leads to compelling device PCEs of 8.48%, in comparison to 7.38% of the reference device (PBDTTT-C-T:PC 71 BM, fabricated and tested under the same conditions). This study thus demonstrates a novel approach to enhance the photovoltaic performance, in combination with 3D urchin-like nanoalloys.