Thermoelectric materials allow for direct conversion between heat and electricity, offering the potential for power generation. The average dimensionless figure of merit ZT ave determines device efficiency. N-type tin selenide crystals exhibit outstanding three-dimensional charge and two-dimensional phonon transport along the out-of-plane direction, contributing to a high maximum figure of merit Z max of ~3.6 × 10 −3 per kelvin but a moderate ZT ave of ~1.1. We found an attractive high Z max of ~4.1 × 10 −3 per kelvin at 748 kelvin and a ZT ave of ~1.7 at 300 to 773 kelvin in chlorine-doped and lead-alloyed tin selenide crystals by phonon-electron decoupling. The chlorine-induced low deformation potential improved the carrier mobility. The lead-induced mass and strain fluctuations reduced the lattice thermal conductivity. Phonon-electron decoupling plays a critical role to achieve high-performance thermoelectrics.
Maximal resection of tumor while preserving the adjacent healthy tissue is particularly important for larynx surgery, hence precise and rapid intraoperative histology of laryngeal tissue is crucial for providing optimal surgical outcomes. We hypothesized that deep-learning based stimulated Raman scattering (SRS) microscopy could provide automated and accurate diagnosis of laryngeal squamous cell carcinoma on fresh, unprocessed surgical specimens without fixation, sectioning or staining. Methods : We first compared 80 pairs of adjacent frozen sections imaged with SRS and standard hematoxylin and eosin histology to evaluate their concordance. We then applied SRS imaging on fresh surgical tissues from 45 patients to reveal key diagnostic features, based on which we have constructed a deep learning based model to generate automated histologic results. 18,750 SRS fields of views were used to train and cross-validate our 34-layered residual convolutional neural network, which was used to classify 33 untrained fresh larynx surgical samples into normal and neoplasia. Furthermore, we simulated intraoperative evaluation of resection margins on totally removed larynxes. Results : We demonstrated near-perfect diagnostic concordance (Cohen's kappa, κ > 0.90) between SRS and standard histology as evaluated by three pathologists. And deep-learning based SRS correctly classified 33 independent surgical specimens with 100% accuracy. We also demonstrated that our method could identify tissue neoplasia at the simulated resection margins that appear grossly normal with naked eyes. Conclusion : Our results indicated that SRS histology integrated with deep learning algorithm provides potential for delivering rapid intraoperative diagnosis that could aid the surgical management of laryngeal cancer.
Thermoelectric technology has been widely used for key areas, including waste-heat recovery and solid-state cooling. We discovered tin selenide (SnSe) crystals with potential power generation and Peltier cooling performance. The extensive off-stoichiometric defects have a larger impact on the transport properties of SnSe, which motivated us to develop a lattice plainification strategy for defects engineering. We demonstrated that Cu can fill Sn vacancies to weaken defects scattering and boost carrier mobility, facilitating a power factor exceeding ~100 microwatts per centimeter per square kelvin and a dimensionless figure of merit ( ZT ) of ~1.5 at 300 kelvin, with an average ZT of ~2.2 at 300 to 773 kelvin. We further realized a single-leg efficiency of ~12.2% under a temperature difference (Δ T ) of ~300 kelvin and a seven-pair Peltier cooling Δ T max of ~61.2 kelvin at ambient temperature. Our observations are important for practical applications of SnSe crystals in power generation as well as electronic cooling.
coefficient, σ represents electrical conductivity, T represents working temperature in Kelvin, κ ele denotes electronic thermal conductivity, and κ lat denotes lattice thermal conductivity. [4,5] Extensive efforts are devoted to decoupling these correlative parameters. [6] Electrically, the strategies of band convergence, [2] band alignment, [4,7] densityof-states (DOS) distortion, [8,9] modulation doping, [10] enhancing the symmetry of crystal [11] and quantum confinement [12] are successfully established to equilibrate the Seebeck coefficient (S) and the electrical conductivity (σ) in favor of a superior power factor (PF). [13] It is well known that the enhanced band degeneracy due to band convergence could increase the effective mass a bit without degrading the carrier mobility. And DOS distortion, which improves the band effective mass, is a feasible strategy with risks for deteriorating the carrier mobility. [14] It is clear that the optimal balance between the effective mass and the carrier mobility is beneficial for the electrical performance of TE materials. This relationship primarily depends on the weighted mobility, µW = μ H (m * /m e ) 3/2 , where μ H represents the carrier mobility, m * represents the DOS effective mass, and m e represents the unit electron mass.Thermally, intensifying the phonon scattering is considered to be an effective method to decrease the thermal conductivity (κ lat ), which is generally classified into incorporating extra phonon scattering centers [15] and seeking inherent low lattice thermal conductivity materials. [16,17] The latter representing materials might have a complex crystal structure, [1] heavy constituent elements, [18] intense lattice anharmonicity, [19] and soft chemical bonding. [20] And the extra phonon scattering sources include point defects, nanoprecipitates, grain boundaries, and so on. [21] To date, state-of-the-art TE materials, including Zintl phase, [22] half-Heusler, [23] skutterudite, [24] SiGe, [25] chalcogenides, [8,26] and Bi 2 Te 3 -based compounds, [27] etc., exhibit prominent thermoelectric performance.GeTe is proven to be an eminent mid-temperature thermoelectric material. [28,29] The well-recognized characters of GeTe are multiple valance bands, phase transition, ultrahigh carrier concentration, and high thermal conductivity, which diversify the degrees of freedom to tailor its TE performance. [30][31][32] Counter-doping using aliovalent elements, such as Bi, Sb, and In, [33,34] is a common method to achieve the optimal carrier Thermoelectric materials can achieve the direct conversion between electricity and heat, which has drawn extensive attention in recent decades. Understanding the chemical nature of band structure and microstructure is essential to boost the thermoelectric performance of given materials. Herein, CdSe alloying promotes the evolution of multiple valence bands in GeTe, resulting in the contemporaneous appearance of band convergence and density of state distortion, which benefits the sharply enhanced effective mass from ...
Thermoelectric generators enable the conversion of waste heat to electricity, which is an effective way to alleviate the global energy crisis. However, the inefficiency of thermoelectric materials is the main obstacle for realizing their widespread applications and thus developing materials with high thermoelectric performance is urgent. Here we show that multiple valence bands and strong phonon scattering can be realized simultaneously in p-type PbSe through the incorporation of AgInSe2. The multiple valleys enable large weighted mobility, indicating enhanced electrical properties. Abundant nano-scale precipitates and dislocations result in strong phonon scattering and thus ultralow lattice thermal conductivity. Consequently, we achieve an exceptional ZT of ~ 1.9 at 873 K in p-type PbSe. This work demonstrates that a combination of band manipulation and microstructure engineering can be realized by tuning the composition, which is expected to be a general strategy for improving the thermoelectric performance in bulk materials.
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