Binbin Jiang

Intense short-wavelength photoluminescence from thermal SiO2 films co-implanted with Si and C ions

Intense short-wavelength photoluminescence (PL) observed at room temperature from thermal SiO2 films co-implanted with Si and C is reported. A flat Si profile was first implanted, followed by 1100 °C annealing for 60 min. C ions were subsequently used to be implanted into the same depth region. PL was observed from the as-implanted samples with and without annealing. The PL intensity increases with annealing temperature. Comparing the PL spectra and the PL dynamics of the C-implanted, annealed, Si-implanted (CIASI) SiO2 films with those from Si- and C-implanted SiO2 films suggests that the interaction of Si and C in SiO2 films plays an important role in the luminescence in CIASI SiO2 films.

Entropy as a Gene‐Like Performance Indicator Promoting Thermoelectric Materials

High-throughput explorations of novel thermoelectric materials based on the Materials Genome Initiative paradigm only focus on digging into the structure-property space using nonglobal indicators to design materials with tunable electrical and thermal transport properties. As the genomic units, following the biogene tradition, such indicators include localized crystal structural blocks in real space or band degeneracy at certain points in reciprocal space. However, this nonglobal approach does not consider how real materials differentiate from others. Here, this study successfully develops a strategy of using entropy as the global gene-like performance indicator that shows how multicomponent thermoelectric materials with high entropy can be designed via a high-throughput screening method. Optimizing entropy works as an effective guide to greatly improve the thermoelectric performance through either a significantly depressed lattice thermal conductivity down to its theoretical minimum value and/or via enhancing the crystal structure symmetry to yield large Seebeck coefficients. The entropy engineering using multicomponent crystal structures or other possible techniques provides a new avenue for an improvement of the thermoelectric performance beyond the current methods and approaches.

Cu8GeSe6-based thermoelectric materials with an argyrodite structure

Recently, liquid-like superionic thermoelectric materials have attracted great attention due to their extremely low lattice thermal conductivity and high thermoelectric figure of merit (ZT). Argyrodite-type compounds are typical superionic semiconductors with two independent structural units that can be used to separately tune electrical and thermal transport properties. In this work, we report that Cu8GeSe6 with an argyrodite structure is a new class of thermoelectric materials with extremely low lattice thermal conductivity. The presence of two independent structural units in Cu8GeSe6 provides the possibility of greatly improving its electrical transport properties while maintaining ultralow lattice thermal conductivity. By alloying Ag and Te in Cu8GeSe6, the ZT values are significantly improved to above unity at 800 K in Cu7.6Ag0.4GeSe5.1Te0.9, comparable with the best superionic liquid-like thermoelectric materials. The ultralow thermal conductivity is mainly attributed to the weak chemical bonding between Cu atoms and the rigid [GeSe6] sublattice.

Copper chalcogenide thermoelectric materials

Cu-based chalcogenides have received increasing attention as promising thermoelectric materials due to their high efficiency, tunable transport properties, high elemental abundance and low toxicity. In this review, we summarize the recent research progress on this large family compounds covering diamond-like chalcogenides and liquid-like Cu2X (X=S, Se, Te) binary compounds as well as their multinary derivatives. These materials have the general features of two sublattices to decouple electron and phonon transport properties. On the one hand, the complex crystal structure and the disordered or even liquid-like sublattice bring about an intrinsically low lattice thermal conductivity. On the other hand, the rigid sublattice constitutes the charge-transport network, maintaining a decent electrical performance. For specific material systems, we demonstrate their unique structural features and outline the structure-performance correlation. Various design strategies including doping, alloying, band engineering and nanostructure architecture, covering nearly all the material scale, are also presented. Finally, the potential of the application of Cu-based chalcogenides as high-performance thermoelectric materials is briefly discussed from material design to device development.摘要铜基硫族化合物因其高性能、可调的输运性质、高丰度和低毒性, 被认为是很有前景的新型热电材料, 引起了研究者的广泛关注.本文总结了近年来铜基热电材料的研究进展, 包括类金刚石结构材料、声子液体二元及多元化合物等. 本文首先总体介绍了两套亚晶格的基本特征及其对热学、电学性质的影响: 一方面, 复杂晶体结构和无序、甚至液态化的亚晶格导致极低的热导率; 另一方面, 刚性亚晶格构成电荷传输通道, 保证了较高的电学性能. 然后, 本文针对特定的几类材料体系, 详细介绍了其典型结构特征与“结构-性能”构效关系, 以及掺杂、固溶、能带结构调控和纳米结构设计等多尺度优化手段. 最后, 本文从材料研发和器件研制的角度评述了铜基硫族化合物作为热电材料的应用前景及相关进展.

Significantly optimized thermoelectric properties in high-symmetry cubic Cu7PSe6 compounds via entropy engineering

High-symmetry crystal structures are preferred for thermoelectrics because high structural symmetry usually yields good electron transport properties. Entropy engineering is an effective approach to improve the structural symmetry of low-symmetry materials, and thus to enhance their thermoelectric performance. In this study, via introducing Te into the argyrodite-type compound Cu7PSe6, the configurational entropy is significantly increased to successfully improve its initial low-symmetry cubic structure (P213) to the high-symmetry cubic structure (F3m) at room temperature. Such improved structural symmetry leads to a high density-of-state effective mass but similar carrier mobility in the same carrier concentration range as compared with the pristine Cu7PSe6. Thus, significantly optimized electron transport properties are achieved in the Te-alloyed Cu7PSe6 samples. In particular, at room temperature, the power factor of the high-symmetry cubic Cu7PSe5.7Te0.3 sample is about 15-times higher than that of the low-symmetry Cu7PSe6 matrix. Combining the well-maintained ultralow lattice thermal conductivity, a maximum ZT of around 0.55 at 600 K is obtained in Cu7PSe5.7Te0.3. This work strongly shows that entropy engineering using multiple components is a very powerful strategy to discover or design novel high-performance TE materials starting from low-symmetry compounds.

Phonon anharmonicity in thermoelectric palladium sulfide by Raman spectroscopy

Recent advances in the study of thermoelectric materials mainly focus on the developments or designs of methods to reduce thermal conductivities. The information of phonon scattering processes is the key to the understanding of the thermal transfer and transport of a material. Such information is essential for the understanding of the thermal conductivity of a material itself and for the further improvement to demand the requirements for technological applications. Recently, palladium sulfide has been examined as a potential thermoelectric material. However, the high thermal conductivity limits its thermoelectric performance and technological applications. Here, Raman scattering spectroscopy is used to investigate the thermal transport properties of this material over a wide range of temperatures. The nonlinear temperature-dependent frequencies and linewidths of the Raman modes illustrate the anharmonicity of phonon scattering for thermal transport in this material. Three-phonon scattering processes are found to account for the thermal transport in the temperature range of 10–620 K. The high-energy bands of the Bg mode related to the light atom (S) contribute most to the thermal transport properties. More phonon scattering processes including higher orders are seemingly needed to further reduce the thermal conductivity of this material.Recent advances in the study of thermoelectric materials mainly focus on the developments or designs of methods to reduce thermal conductivities. The information of phonon scattering processes is the key to the understanding of the thermal transfer and transport of a material. Such information is essential for the understanding of the thermal conductivity of a material itself and for the further improvement to demand the requirements for technological applications. Recently, palladium sulfide has been examined as a potential thermoelectric material. However, the high thermal conductivity limits its thermoelectric performance and technological applications. Here, Raman scattering spectroscopy is used to investigate the thermal transport properties of this material over a wide range of temperatures. The nonlinear temperature-dependent frequencies and linewidths of the Raman modes illustrate the anharmonicity of phonon scattering for thermal transport in this material. Three-phonon scattering processes are f...