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Optimizing carrier concentration in PbTe materials can be achieved effectively through the chemical doping of sodium. Nevertheless, the valence balance can lead to the presence of "deleterious defects" in the PbTe matrix, resulting in low sodium solubility at room temperature. Herein, a strategy for fine‐tuning Pb vacancies to improve sodium solubility is developed. By a trace amount of Se‐doping, the solubility of Na in Pb0.99Te1‐xSex through the preservation of Pb vacancies in the matrix is substantially increased. Additionally, a large number of dense dislocations in the grains, which greatly reduced the lattice thermal conductivity is induced. A high power factor of ≈26 mW cm−1 K−2 and low lattice thermal conductivity of ≈0.43 W m−1 K−1 at 823 K in Pb0.95Na0.04Te0.97Se0.03 is achieved. Ultimately, a high figure of merit, ZT ≈2.2, is obtained at 823 K in quaternary PbTe compound. The current findings not only demonstrate that the introduction of trace amounts of Se and Pb vacancies in the PbTe matrix can effectively enhance Na solubility and minimize thermal conductivity, attaining synergistic improvement in electrical and thermal properties, but also indicate that the synergistic effect of Pb vacancies with a specific dopant is an alternative approach for enhancing ZT. [ABSTRACT FROM AUTHOR]

Content: In this thesis, the role of N atom doping and biaxial strain in modulating the electronic structure and optical properties of antimonene has been deeply investigated using a first-principles approach based on density-functional theory. The results show that N doping significantly reduces the band gap of antimonene and introduces new electronic states, thus affecting its electronic structure. In terms of optical properties, N doping reduces the static permittivity of antimonene and alters its absorption, reflection, and energy loss properties. In addition, biaxial strain further enhanced the modulation effect of these properties. This study not only provides theoretical support for the application of antimonene in the field of high-performance two-dimensional electronic and optoelectronic devices, but also reveals strain and doping as an effective means to modulate the physical properties of two-dimensional materials. Methods: For the calculations, we used the DFT-based CASTEP software package for the simulation of the electronic structure. In order to more accurately characterize the weak interactions between two-dimensional materials, we specifically introduced the Van der Waals dispersion correction. We have chosen the Perdew-Burke-Ernzerhof (PBE) exchange-correlation generalization under the generalized gradient approximation (GGA) and combined it with the Van der Waals correction term in order to fully consider the electronic structure of antimonene. For the calculation parameter settings, we set the truncation energy to 400 eV to ensure the accuracy of the calculation. Meanwhile, we adopt a 6 × 6 × 1 k-point grid for Brillouin zone sampling to obtain more accurate energy band structure and density of states information. For the convergence settings, the convergence criteria for both the system energy and the interaction force between atoms were set to 1 × 10−5 eV and 0.01 eV/Å, respectively. We selected a 3 × 3 × 1 supercell model with 18 Sb atoms. A vacuum thickness of 18 Å was established in the Z direction, which is sufficient to avoid interactions between the two atomic layers above and below the periodic structure. [ABSTRACT FROM AUTHOR]

Finding a real thermoelectric (TE) material that excels in various aspects of TE performance, mechanical properties, TE power generation, and cooling is challenging for its commercialization. Herein, we report a novel multifunctional Ge0.78Cd0.06Pb0.1Sb0.06Te material with excellent TE performance and mechanical strength, which is utilized to construct candidate TE power generation and cooling devices near room temperature. Specifically, the effectiveness of band convergence, combined with optimized carrier concentration and electronic quality factor, distinctly boosts the Seebeck coefficient, thus greatly improving the power factor. Advanced electron microscopy observation indicates that complex multi‐scale hierarchical structures and strain field distributions lead to ultra‐low lattice thermal conductivity, and also effectively enhance mechanical properties. High ZT ~ 0.6 at 303 K, average ZTave ~ 1.18 from 303 to 553 K, and Vickers hardness of ~200 Hv in Ge0.78Cd0.06Pb0.1Sb0.06Te are obtained synchronously. Particularly, a 7‐pair TE cooling device with a maximum ΔT of ~45.9 K at Th = 328 K, and a conversion efficiency of ~5.2% at Th = 553 K achieving in a single‐leg device. The present findings demonstrate a unique approach to developing superior multifunctional GeTe‐based alloys, opening up a promising avenue for commercial applications. [ABSTRACT FROM AUTHOR]

GeSb2Te4 (GST124), one of the well‐known phase‐change materials for nonvolatile memory and rewritable optical storage, has been recently found to be promising thermoelectric materials with low lattice thermal conductivity and high electrical conductivity. However, its thermoelectric performance is greatly restricted by the excessively high hole concentration. Herein, the impact of a series of group IIIA (Al, Ga, In) and group VIA (S, Se) dopants on the electrical transport properties of polycrystalline GST124 has been studied. It is found that element sulfur (S) has the best doping efficiency because the GeS bonds are very strong and ionic that are beneficial for suppressing Ge vacancies to reduce the carrier concentration. Meanwhile, element indium (In) also shows decent doping efficiency because its ionic radius is close to the Ge ion and the InTe bonds have moderate bonding strength. Moreover, In doping introduces a resonant level in the valence band, leading to enhanced Seebeck coefficient and power factor. A high figure of merit (zT)of 0.73 at 700 K and an average zT of 0.48 over 300–750 K are obtained in Ge0.92In0.08Sb2Te4, which are 26% and 66% higher than pristine GST124. This study will advance the understanding and development of high‐performance GeSbTe‐based thermoelectric materials. [ABSTRACT FROM AUTHOR]

In recent years, organic-inorganic hybrid lead halide perovskite materials have attracted much attention in the world because of their excellent photoelectric properties, and have been successfully applied in many fields such as solar photovoltaic, photoelectric detection, electroluminescence and so on. At present, most of the device research focuses on perovskite polycrystalline materials, but perovskite single crystal materials have excellent properties such as lower defect state density, higher carrier mobility, longer carrier recombination lifetime, wider light absorption range and higher stability, which can effectively reduce the scattering loss during carrier transport and non-radiative recombination at the grain boundary, and inhibit the hysteresis effect caused by ion migration. Using perovskite single crystal thin film as the active layer of the device is expected to produce more efficient and stable perovskite photoelectric devices. At present, many preparation methods of perovskite single crystal films have been reported, mainly including solution-processed space-confined method, chemical vapor deposition method, top-down processing method, etc. Among them, solution-processed space-confined method is the most widely developed and applied. This paper focuses on the preparation of high-quality perovskite single crystal thin films by solution-processed space-confined method, and the research progress of perovskite single crystal thin films in photodetectors, solar cells, field effect transistors, light-emitting diodes and other related devices, and prospects the future development trend of perovskite single crystal thin films and photoelectric devices. [ABSTRACT FROM AUTHOR]

Hematite (α-Fe2O3) has emerged as a promising candidate for photoelectrochemical (PEC) water oxidation. Modulating its composition is pivotal for obtaining highly efficient PEC performance. However, an oxygen-rich surface is formed from the FeOOH precursor, resulting in poor surface charge transfer. In this work, for the first time, Fe nanoparticles were deposited on the surface of α-Fe2O3 to increase the atomic ratio of Fe to O on the surface. Subsequently, oxygen vacancy (VO) and hydrogen (H) impurity defects were introduced to further control the chemical composition of Fe2O3. The introduction of VO can increase the charge carrier density, while the charge transport mobility is reduced due to the low hopping process of small polarons induced by VO. To address the problem, we show that shallow-level defects are created via H doping, which extracts the trapped electrons out of the VO-induced trap states. Due to the formation of homogeneous distribution of Fe and O, introduction of VO and incorporation of shallow-level defects by H impurity, charge separation efficiency was markedly improved. Consequently, the photocurrent density of the α-Fe2O3 photoanode was increased from 0.76 to 1.71 mA cm−2 at a potential of 1.23 V versus the reversible hydrogen electrode. Our work verifies the relationship between the PEC performance of the semiconductor photoanode and its composition and provides promising opportunities for further optimization. [ABSTRACT FROM AUTHOR]

Background: In time‐of‐flight PET, image quality and accuracy can be enhanced by improving the annihilation photon pair coincidence time resolution, which is the variation in the arrival time difference between the two annihilation photons emitted from each positron decay in the patient. Recent studies suggest direct detection of ionization tracks and their resulting modulation of optical properties, instead of scintillation, can improve the CTR significantly, potentially down to less than 10 ps CTR. However, the arrival times of the 511 keV photons are not predictable, leading to challenges in the spatiotemporal localization characterization of the induced charge carriers in the detector crystal. Purpose: To establish an optimized experimental setup for measuring ionization induced modulation of optical properties, it is critical to develop a versatile simulation algorithm that can handle multiple detector material properties and time‐resolved charge carrier dynamics. Methods: We expanded our previous algorithm and simulated ionization tracks, cascade time and induced charge carrier density over time in different materials. For designing a proof‐of‐concept experiment, we simulated ultrafast electrons and free‐electron x‐ray photons for timing characterization along with alpha and beta particles for higher spatial localization. Results: With 3 MeV ultrafast electrons, by reducing detector crystal thickness, we can effectively reduce the ionization cascade time to 0.79 ps and deposited energy to 198.5 keV, which is on the order of the desired 511 keV energy. Alpha source simulations produced a cascade time of 2.45 ps and charge carrier density of 6.39 × 1020 cm−3. Compared to the previous results obtained from 511 keV photon‐induced ionization track simulations, the cascade time displayed similar characteristics, while the charge density was found to be higher. These findings suggest that alpha sources have the potential to generate a stronger ionization‐induced signal using the modulation of optical properties as the detection mechanism. Conclusions: This work provides a guideline to understand, design and optimize an experimental platform that is highly sensitive and temporally precise enough to detect single 511 keV photon interactions with a goal to advance CTR for ToF‐PET. [ABSTRACT FROM AUTHOR]

Mixtures of layered perovskite quantum wells with different sizes form prototypical light-harvesting antenna structures in solution-processed films. Gradients in the bandgaps and energy levels are established by concentrating the smallest and largest quantum wells near opposing electrodes in photovoltaic devices. Whereas short-range energy and charge carrier funneling behaviors have been observed in layered perovskites, our recent work suggests that such light-harvesting processes do not assist long-range charge transport due to carrier trapping at interfaces between quantum wells and interstitial organic spacer molecules. Here, we apply a two-pulse time-of-flight technique to a family of layered perovskite systems to explore the effects that interstitial organic molecules have on charge carrier dynamics. In these experiments, the first laser pulse initiates carrier drift within the active layer of a photovoltaic device, whereas the second pulse probes the transient concentrations of photoexcited carriers as they approach the electrodes. The instantaneous drift velocities determined with this method suggest that the rates of trap-induced carrier deceleration increase with the concentrations of organic spacer cations. Overall, our experimental results and model calculations suggest that the layered perovskite device efficiencies primarily reflect the dynamics of carrier trapping at interfaces between quantum wells and interstitial organic phases. [ABSTRACT FROM AUTHOR]

The polycrystalline SnS with a similar layered crystal structure and band structure to SnSe exhibits enormous commercial thermoelectric potential due to its lower cost and environmentally friendly characteristics. However, the wider bandgap of SnS leads to low carrier concentration and inferior electrical transport performance. The two-dimensional interlayer hinders carrier transport, leading to interesting and mysterious anisotropic thermoelectric properties. Herein, we reported the optimized electron–phonon transport in anisotropic polycrystalline SnS by Ag doping and Se alloying, realizing a high quality factor B by multiple strategies of optimizing carrier concentration, modifying band structure, and introducing various defects; further potential performance is predicted by the single parabolic band model. Specifically, Ag-doped SnS not only significantly increases the carrier concentration and weighted mobility μw in both directions but also induces multi-scale precipitates proven by the Debye–Callaway model to suppress phonon transport. Moreover, additional Se alloying optimizes the electronic band structure and increases the Seebeck coefficient, further improving μW and boosting the maximum power factor to ∼3.72 μW cm−1 K−2 at 873 K in the out-of-plane direction. Consequently, the synergistic optimization of carrier and phonon transport achieved a high B of 0.7 and a maximum zTmax of ∼0.8 at 873 K in Ag0.02Sn0.98S0.99Se0.01. Additionally, the high B predicted a high zTmax∼1.5 based on optimized carrier transport characteristics, demonstrating the potential great-performance polycrystalline SnS. This work provides a promising avenue for optimizing the zT of polycrystalline SnS by transport engineering. [ABSTRACT FROM AUTHOR]

The thermoelectric figure-of-merit (zT) of p-type MNiSn (M = Ti, Zr, or Hf) half-Heusler compounds is lower than their η-type counterparts due to the presence of a donor in-gap state caused by Ni occupying tetrahedral interstitials. While ZrNiSn and TiNiSn, have been extensively studied, HfNiSn remains unexplored. Herein, this study reports an improved thermoelectric property in p-type HfNi1-xCoxSn. By doping 5 at% Co at the Ni sites, the Seebeck coefficient becomes reaching a peak value exceeding 200 μV K-1 that breaks the record of previous reports. A maximum power factor of ≈2.2 mW m-1 K-2 at 973 K is achieved by optimizing the carrier concentration. The enhanced p-type transport is ascribed to the reduced content of Ni defects, supported by first principle calculations and diffraction pattern refinement. Concomitantly, Co doping also softens the lattice and scatters phonons, resulting in a minimum lattice thermal conductivity of ≈1.8 W m-1 K-1. This leads to a peak zT of 0.55 at 973 K is realized, surpassing the best performing p-type MNiSn by 100%. This approach offers a new method to manipulate the intrinsic atomic disorder in half-Heusler materials, facilitating further optimization of their electronic and thermal properties. [ABSTRACT FROM AUTHOR]

Transition metals have excellent valence electrical properties and unique electronic state distribution and are regarded as potential materials for improving thermoelectric performance. However, the impact of transition metals on thermoelectric materials is restricted to the solid solution limit and doping efficiency, reinforcing the shortcomings in systematic research. Here, thermoelectric properties of transition metal (Ti, V, Cr, Zr, Nb, Mo)-doped PbS are compared and analyzed systematically based on the formation enthalpy. The DFT calculation indicates that the doping (except Zr) leads to the bandgap expansion and the density of states distortion near the Fermi level, while the localization property of the latter results in an invalid resonance level. The formation enthalpy dominates the carrier concentration due to the opposite trend of carrier concentration and formation enthalpy. The formation enthalpy of Zr, Ti, and Nb doping is more negative than others, leading to the more significant optimization of carrier concentration. The Moss–Burstein effect promotes the bandgap expansion, leading to weaker bipolar effects for Zr, Ti, and Nb doping. Eventually, the thermoelectric performance for Ti, Zr, and Nb doping is superior to others at high temperature. The Hume-Rothery rule of the formation enthalpy supplementation is more suitable for the doping and alloying in thermoelectricity. Thermodynamic stability analysis based on the formation enthalpy contribute the PbS-based thermoelectric devices evaluation. The present finding demonstrates the significant effect of formation enthalpy on the thermoelectric properties of PbS and provides a useful avenue for the doping modification and thermodynamic stability analysis of other thermoelectric alloy materials. [ABSTRACT FROM AUTHOR]

As a member of the emerging MXenes family, Nb2CS2 offers distinctive superconductivity, excellent electrical properties, and outstanding chemical stability, making it potentially useful for energy storage, medical imaging, and quantum computing. Herein, we systematically investigate how ultrahigh pressure affects the electrical properties of Nb2CS2. The results indicate that Nb2CS2 retains robust superconductivity with T c > 8 K up to the maximum applied pressure of 146.8 GPa. Moreover, the upper critical magnetic field H c 2 (0) of Nb2CS2 increases with pressure, and the Pauli limit is violated at pressures greater than 120 GPa. Meanwhile, H c 2 (0) increases to 19.3 T at 146.8 GPa, which is 4.8 times greater than at the initial pressure. Further analysis suggests that the significant enhancement of H c 2 (0) below 30 GPa comes from the sharp pressure-induced rise of carrier concentration as the interlayer distance decreases, and the significant increase in H c 2 (0) above 86 GPa may come from enhanced spin–orbit coupling or the possible unconventional superconducting pairing mechanisms. These results provide insights into the superconducting properties of MXene materials and offer guidelines for further research on electronic transport in Mxenes under ultrahigh pressure. [ABSTRACT FROM AUTHOR]

Hole transport materials are crucial for efficient charge extraction in perovskite solar cells to achieve high power conversion efficiency and stability. Herein, the hole transport properties of the 2,2′,7,7′-tetrakis-(N,N-di-p-methoxyphenylamine)9,9′-spirobifluorene (spiro-OMeTAD) thin films with a dopant lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) are investigated through impedance spectroscopy. Upon doping, we observe a dispersive hole transport with nearly a 100-fold increase in the hole mobility compared with the pristine spiro-OMeTAD films. The hole mobilities slightly decrease with increasing electric fields for both films, exhibiting a negative electric field dependence of mobility due to the positional disorder. Subsequently, the charge carrier density of the LiTFSI-doped spiro-OMeTAD film is three orders of magnitude higher than that of the pristine film. The LiTFSI dopant induces two different electrical regions in the doped thin film, which can be reflected through impedance spectroscopy. The presented investigation through impedance spectroscopy is of high practical interest for the development of hole transport materials and the optimization of the transport layer doping in perovskite solar cells. [ABSTRACT FROM AUTHOR]

Ge-Sb-Te compounds (GST), the well-known phase-change materials, are considered to be promising thermoelectric (TE) materials due to their decent thermoelectric performance. While Ge2Sb2Te5 and GeSb2Te4 have been extensively studied, the TE performance of GeSb4Te7 has not been well explored. Reducing the excessive carrier concentration is crucial to improving TE performance for GeSb4Te7. In this work, we synthesize a series of Se-alloyed GeSb4Te7 compounds and systematically investigate their structures and transport properties. Raman analysis reveals that Se alloying introduces a new vibrational mode of GeSe2, enhancing the interatomic interaction forces within the layers and leading to the reduction of carrier concentration. Additionally, Se alloying also increases the effective mass and thus improves the Seebeck coefficient of GeSb4Te7. The decrease in carrier concentration reduces the carrier thermal conductivity, depressing the total thermal conductivity. Finally, a maximum zT value of 0.77 and an average zT value of 0.48 (300–750 K) have been obtained in GeSb4Te5.5Se1.5. This work investigates the Raman vibration modes and the TE performance in Se-alloyed GeSb4Te7 sheddinglight on the performance optimization of other GST materials. [ABSTRACT FROM AUTHOR]

AgCrSe2-based compounds have attracted much attention as an environmentally friendly thermoelectric material in recent years due to the intriguing liquid-like properties. However, the ultra-low carrier concentration and the high AgCr deep-level defects limit the overall thermoelectric performance. Here, we successfully introduced Pb into Ag-deficient Ag0.97CrSe2 alloys to tune the carrier concentration across a broad temperature range. The Pb2+ as an acceptor dopant preferentially occupies Cr sites, boosting the hole carrier concentration to 1.77 × 1019 cm−3 at room temperature. Furthermore, the Pb strongly inhibits the creation of intrinsic AgCr defects, weakens the increased thermal excited ionization with the increasing temperature and slowed the rising trend of the carrier concentration. The designed carrier concentration matches the theoretically predicted optimized one over the entire temperature range, leading to a remarkable enhancement in power factor, especially the maximum power factor of ∼ 500 μW⋅m−1⋅K−2 at 750 K is superior to most previous results. Additionally, the abundant point defects promote phonon scattering, thus reducing the lattice thermal conductivity. As a result, the maximum figure of merit zT (∼ 0.51 at 750 K) is achieved in Ag0.97Cr0.995Pb0.005Se2. This work confirms the feasibility of manipulating deep-level defects to achieve temperature-dependent optimal carrier concentration and provides a valuable guidance for other thermoelectric materials. [ABSTRACT FROM AUTHOR]

The distinguishing feature of a quantum system is interference arising from the wave mechanical nature of particles which is clearly central to macroscopic electronic properties. Here, we report the signature of quantum interference effect in inter-layer transport process. Via systematic magneto-drag experiments on graphene-based electronic double-layer systems, we observe low-field correction to the Coulomb-scattering-dominated inter-layer drag resistance in a wide range of temperature and carrier density, with its characteristics sensitive to the band topology of graphene layers. These observations can be attributed to a new type of quantum interference between drag processes, with the interference pathway comprising different carrier diffusion paths in the two constituent conductors. The emergence of such effect relies on the formation of superimposing planar diffusion paths, among which the impurity potentials from intermediate insulating spacer play an essential role. Our findings establish an ideal platform where the interplay between quantum interference and many-body interaction is essential. Previous demonstrations of quantum interference in solids have mainly been limited to intra-layer transport within single conductors. Zhu et al. report a new type of inter-layer quantum interference in graphene-based double-layer devices, due to interference between carrier diffusion paths across the constituent layers. [ABSTRACT FROM AUTHOR]

Breaking the thermoelectric figure of merit zT barrier of SnTe enables it to become a promising alternative to PbTe; however, the inferior and strongly coupled physicochemical properties of pristine SnTe severely restrict the efficient optimization. Herein, we doped trivalent Sb in SnTe and incorporated SnS particles to achieve high quality factor B through a two-step optimization strategy of tuning the valence band structure and intercalating heterostructural precipitates, and well predicted the potential prospects. The high solubility limit of Sb not only reduced the carrier concentration nH but also significantly optimized the valence band structure and improved the Seebeck coefficient, thereby enhancing the weight mobility μw in the all-temperature region. Furthermore, the additional SnS, which tends to exist as precipitates with different micrometer-scale sizes, enhanced low-medium-frequency phonon scattering in a wider frequency range except for point defects scattering, suppressing the lattice thermal conductivity to 0.55 W m−1 K−1. As a result of this synergistic effect, a high B-factor of ∼0.82 greater than triple pure SnTe was obtained in Sn0.91Sb0.09Te-10%SnS, with an enhanced zT of ∼1.15 at 850 K. More importantly, the high B-factor accurately predicted an excellent zT value of ∼1.65 at the optimal Fermi level, which highlights the great potential of Sn1-xSbxTe-y%SnS-based materials. This work provides an effective route for stepwise optimization of electrical and thermal performance from the B-factor perspective and has guiding significance for other thermoelectric materials. [ABSTRACT FROM AUTHOR]

Diamondlike compound Cu2SnS3 has attracted great attention recently due to its excellent thermoelectric performance and the features of being eco-friendly and low cost. However, the underlying mechanism for its good electrical transports under high carrier concentration range is still not clear. In this work, we synthesized a series of Cu2+xSn1−xS3 (x = 0–0.08) samples. These nonstoichiometric Cu2+xSn1−xS3 samples are polymorph simultaneously crystalizing in the monoclinic, tetragonal, and cubic structures. The characterization on the electrical transports and the analysis on the band structure reveal that the large density-of-states effective mass, high Seebeck coefficient, and high mobility under a high carrier concentration in the Cu2+xSn1−xS3 system are originated from the existence of multiple bands near the edge of the valence band. Likewise, the polymorphic structure has little influence on the electrical transports. A maximum power factor of 12.6 μW cm−1 K−2 at 700 K has been obtained for the nonstoichiometric Cu2.08Sn0.92S3. Combining the low lattice thermal conductivity of these samples, Cu2.08Sn0.92S3 shows a peak dimensionless figure of merit of 0.5 at 700 K. This work is helpful for guiding the future optimization of thermoelectric performance on Cu2SnS3. [ABSTRACT FROM AUTHOR]

As the pseudo-binary alloys between GeTe and Sb2Te3, GeSbTe-based compounds are promising thermoelectric materials. Although Ge2Sb2Te5 and GeSb2Te4 have widely been studied, the thermoelectric properties of GeSb4Te7 have not been well understood yet. In this work, we design a series of GeSb4-xBixTe7 solid solutions and systematically study the variation in the crystal structure, electrical, and thermal transport properties. Alloying Bi effectively reduces the carrier concentration and, thus, enhances the Seebeck coefficient. Meanwhile, the thermal conductivity is greatly reduced via large mass fluctuations. A maximum zT of 0.69 at 550 K and an average zT value of 0.52 between 300 and 700 K have been achieved for GeSb1.5Bi2.5Te7. These findings will promote the understanding and development of GeSbTe-based thermoelectric materials. [ABSTRACT FROM AUTHOR]

Compared with green and red perovskite light‐emitting diodes (PeLEDs), the development of blue PeLEDs has been lagging due to high defect density and inferior carrier transport. Herein, a novel defect‐passivation strategy is proposed to fabricate efficient sky‐blue PeLEDs by using isocyanate molecules. This strategy not only significantly reduces the nonradiative recombination loss caused by defects but also improves the injection and transport capacities of carriers by reducing the confinement effect. Benefiting from the passivation engineering and the reduction of confinement effect, the prepared sky‐blue PeLEDs present a significantly improved external quantum efficiency of 12.5% at 489 nm, which is 1.5 times higher than that of the control device. Meanwhile, the universality of isocyanate‐based passivators to improve the performance of PeLEDs is also demonstrated. The finding of this study provides a new reference for the selection of novel passivation agents to construct highly efficient blue PeLEDs. [ABSTRACT FROM AUTHOR]

The misfit layer compound (SnS)1.2(TiS2)2 is a promising low-cost thermoelectric material because of its low thermal conductivity derived from the superlattice-like structure. However, the strong covalent bonds within each constituent layer highly localize the electrons thereby it is highly challenging to optimize the power factor by doping or alloying. Here, we show that Bi doping at the Sn site markedly breaks the covalent bonds networks and highly delocalizes the electrons. This results in a high charge carrier concentration and enhanced power factor throughout the whole temperature range. It is highly remarkable that Bi doping also significantly reduces the thermal conductivity by suppressing the heat conduction carried by phonons, indicating that it independently modulates phonon and charge transport properties. These effects collectively give rise to a maximum ZT of 0.3 at 720 K. In addition, we apply the single Kane band model and the Debyeâ€"Callaway model to clarify the electron and phonon transport mechanisms in the misfit layer compound (SnS)1.2(TiS2)2. [ABSTRACT FROM AUTHOR]

Mg 3 Sb 2 -based alloys exhibit promising characteristics as thermoelectric materials owing to their non-toxicity, low cost, abundance of earth constituent elements, and high thermoelectric performance. However, the thermoelectric performance of Mg 3 Sb 2 -based films remains challenging due to their inherently low carrier concentration. To address this challenge, this work focuses on elevating the carrier concentration of Mg 3 Sb 2-x Bi x films via alloying Bi in Mg 3 Sb 2. The results demonstrate that the incorporation of the Bi element successfully increases the carrier concentration of Mg 3 Sb 2-x Bi x (x=0, 0.5, 1.5, and 2) films from 1016 cm−3 (x=0) to 1020 cm−3 (x=2). Furthermore, the introduction of Bi in Mg 3 Sb 2-x Bi x films suppresses the phonon transport by enhancing boundary scattering of phonon, leading to a decrease in thermal conductivity. Ultimately, the synergistic optimization drives the peak ZT value to 0.27 for x=1.5 in Mg 3 Sb 2-x Bi x at 525 K, which is more than seven times higher compared to the Mg 3 Sb 2 thin film (ZT ∼0.035 at 525 K). This work has improved the thermoelectric properties of Mg 3 Sb 2 -based films, making an essential contribution to the advancement of Mg 3 Sb 2 -based film materials in the field of Micro-thermoelectric devices. [Display omitted] • The thermoelectric properties of Mg 3 Sb 2-x Bi x thin films were enhanced by phase purification. • Enhanced Power factor comes from increased density of state effective mass by alloying Bi. • Decreased thermal conductivity comes from the suppress of phono transport by alloying effect. [ABSTRACT FROM AUTHOR]

A decrease in valence band energy offset can considerably improve the thermoelectric performance of SnTe, and alloying CdTe in SnTe has been confirmed to be efficient for inducing band convergence. However, the low solubility of CdTe in SnTe severely limits the further decrease in the energy offset and the reduction of lattice thermal conductivity. Inspired by the high solubility of Sb in SnTe-based thermoelectric materials, the trivalent Sb is introduced into SnTe–CdTe alloys, aiming at manipulating the thermoelectric transport properties. Combined with the valence band model, it is demonstrated that high concentration of Sb in SnTe–CdTe enables a further optimization in valence band structures, resulting in an improvement in density-of-state effective mass, thus significantly reinforces the power factor in the whole temperature range. Meanwhile, we propose the solid solution mode of Sb in SnTe, which always generates vacancies to balance the valence state, and the introduction of vacancies explains the reduced lattice parameters and almost constant carrier concentration. Particularly, the Debye–Callaway model quantitatively compares the contribution of Sb substitutional defects and vacancy defects. As a result, an enhanced zT of ∼1.1 has been achieved for Sn0.83Cd0.05Sb0.12Te at 823 K. This work clearly shows the critical role of Sb for enhancing the thermoelectric performance of SnTe–CdTe materials. [ABSTRACT FROM AUTHOR]

AgCrSe2, which crystallizes in alternative layers of Ag+ and CrSe2− octahedral structure, has shown great potential as good thermoelectric material due to its unique ultralow lattice thermal conductivity. In this work, compound Cr2/3Te is alloyed with the matrix Ag0.97CrSe2 and the carrier concentration ranges within 1018–1020 cm−3, enabling a reliable assessment of transport properties based on single parabolic band model at room temperature. Moreover, homogeneous nanoprecipitate is observed in the matrix for high Cr2/3Te content samples, which leads to the scattering of main heat carrier of long-wavelength phonons, and thus a slight reduction of lattice thermal conductivity (∼0.3 W/m K) compared with intrinsic AgCrSe2. Combined with the optimized carrier concentration and the low lattice thermal conductivity, a figure of merit zT of 0.6 at 650 K is achieved, exceeding other reported AgCrSe2 systems, demonstrating the current Ag0.97CrSe2(Cr2/3Te)x materials as good potential thermoelectrics. [ABSTRACT FROM AUTHOR]

Possible mechanism diagram of the roles of oxygen vacancies in LaFeO 3 photocathodes in photoelectrochemical water splitting. [Display omitted] • A molten salt method for preparing Vo modified LaFeO 3 was demonstrated. • Proper amount of Vo can enhance bulk conductivity and light utilization of LaFeO 3. • The charge carrier density of LaFeO 3 in PEC reaction is not in line with the amount of Vo. • The optimal Vo loaded LaFeO 3 exhibits 3.27 times IPCE higher than that of the pristine LaFeO 3. In this study, we prepared oxygen vacancies (V O) modified LaFeO 3 particles using a simple molten salt method by tuning the cation (La3+) deficiency. The existence of V O was confirmed by studying its crystal structure and surface chemical state. By testing the photoelectrochemical (PEC) activity of the Vo modified La 1-x FeO 3-σ photocathodes in a 0.1 M NaOH electrolyte under visible light, the results demonstrate that the as-prepared La 0.9 FeO 3-σ shows good stability and superior IPCE, which is 3.27 times that of the pristine LaFeO 3. Even through V O modification is an effective strategy for regulating the PEC performance of a semiconductor, the charge carrier density in semiconductor is not directly proportional to the amount of V O , as excessive V O may lead to deterioration of the electrochemical reaction due to interfacial charge recombination. Introducing suitable amount of V O into LaFeO 3 can improve the light absorption, boost charge carrier transfer and separation efficiency, narrow the bandgap, and enhance the electrocatalytic reaction dynamics at the semiconductor surface. [ABSTRACT FROM AUTHOR]

Anisotropic tuning is of crucial importance for designing and developing high‐performance thermoelectric materials. Here, a prominent anisotropic thermoelectric characteristic of Ag‐substituted misfit‐layered (SnS)1.2(TiS2)2 alloys is investigated in the perpendicular (in‐plane) and parallel (out‐of‐plane) to the pressing direction. In the in‐plane direction, the (AgxSn1‐xS)1.2(TiS2)2 alloys possess a highest power factor of 0.86 mW K−2 m−1 at 520 K, while in the out‐of‐plane direction the lowest lattice thermal conductivity (0.37 W K−1 m−1) is achieved, which is driven by the natural intercalated structure where the out‐of‐plane phonon is strongly scattered without affecting the in‐plane mobility. Moreover, along the in‐plane orientation, the introduced point defects due to the substitution of Sn by Ag trigger a significant reduction of lattice thermal conductivity. In contrast, along the out‐of‐plane orientation, the decreased carrier concentration enables a large Seebeck coefficient and power factor, ultimately ensuring high thermoelectric performance. The present finding in the misfit‐layered chalcogenide opens up a new route to manipulating thermoelectrics via anisotropy engineering. [ABSTRACT FROM AUTHOR]

The rich capabilities for both electronic and phonon engineering in SnTe are highly desirable for achieving high thermoelectric performance. Alloying high-solubility MnTe (∼15%) leads to substitutional defects for reducing lattice thermal conductivity and band convergence for enhancing electronic performance, and thus, an improvement of thermoelectric performance of SnTe is realized. However, there is no evidence that the electronic and phonon transport properties are fully optimized in SnTe-15%MnTe thermoelectrics, especially for the near-room-temperature (< 573 K) thermoelectric performance, which still needs a sufficient promotion. Here, the substituted 2% Bi in SnTe-15%MnTe alloys dramatically increases the near-room-temperature zT and peak zT to ∼0.72 (at 550 K) and ∼1.3 (at 850 K), respectively. Combining the experimental evidence and the first-principles calculations, we demonstrate that the prominent enhancement of electronic performance arises from the Bi-doping-driven transport valence band alignment and the carrier concentration optimization. Furthermore, the Debye–Callaway model verifies that the reduction in lattice thermal conductivity is dominated by the Bi substitutional defects. The present findings reveal the importance of transport engineering in achieving high thermoelectric performance particularly near room temperature. [ABSTRACT FROM AUTHOR]

AgCrSe2 materials have shown the potential to be the promising thermoelectric materials due to the intrinsic ultralow lattice thermal conductivity enabled by the fluid-like motion of Ag ions in crystal structures. However, what important role the Ag point defects can play in promoting liquid-like conduction still remains a mystery. Moreover, understanding the electronic transport properties, specifically for clarifying the contribution of various impurity states, is of critical importance for improving the thermoelectric performance of AgCrSe2. Here, the thermoelectric properties of AgCrSe2 with various Ag content have been systematically investigated. It is found that the carrier concentration can be modulated in a broad range by inducing deep level impurity states, enabling a transition from degenerate semiconductor to nondegenerate one and a reliable evaluation on the thermoelectric transport properties. The single parabolic band model gives a good clarification regarding the increased electronic performance. Furthermore, the enhancement of the liquid-like effect triggered by the Ag vacancies contributes to the ultralow lattice thermal conductivity (∼0.25 W m−1 K−1). Eventually, a maximum figure of merit zT of ∼0.6 is realized in Ag0.97CrSe2 at 750 K. The present findings may shed light on the improvement of thermoelectric performance in AgCrSe2 materials. [ABSTRACT FROM AUTHOR]

Numerous endeavors have been made to advance thermoelectric SnTe for potential applications. Effective strategies focus on the manipulation of transport properties, including valence band convergence, resonate state, and defect engineering. It has been demonstrated that alloying trivalent Bi or chalcogenide SnSe alone in SnTe can trigger an inherent enhancement of thermoelectric performance. However, what the critical role in the transport valence band co-doping Bi and Se in SnTe plays is still unclear. Particularly, fully evaluating the effect of band convergence on the carrier concentration-dependent weighted mobility, which dominates the electronic performance, is primary and essential for designing excellent thermoelectric materials. Here, we report that Bi doping in SnTe–SnSe alloys can derive a distinct decrease in the energy offset between the two valence bands, thus improving the density-of-state effective mass by only slightly deteriorating the mobility. The well-established theoretical model reveals that the Bi-doping-induced band convergence and the optimized carrier concentration actually enhance the weighted mobility, contributing to the improvement of electronic performance. Moreover, the Debye–Callaway model demonstrates the origin of the reduced lattice thermal conductivity. The present results confirm the potential of transport engineering in promoting thermoelectric performance. [ABSTRACT FROM AUTHOR]

This study presents a new method for measuring the Seebeck coefficient under high pressure in a multi-anvil apparatus. The application of a dual-heating system enables precise control of the temperature difference between both ends of the sample in a high-pressure environment. Two pairs of W–Re thermocouples were employed at both ends of the sample to monitor and control the temperature difference, and independent probes were arranged to monitor the electromotive force (emf) produced by temperature oscillation at a given target temperature. The temperature difference was controlled within 1 K during the resistivity measurements to eliminate the influence of the emf owing to a sample temperature gradient. The Seebeck measurement was successfully measured from room temperature to 1400 K and was obtained by averaging the two measured values with opposite thermal gradient directions (∼20 K). Thermoelectric properties were measured on disk-shaped p-type Si wafers with two different carrier concentrations as a reference for high Seebeck coefficients. This method is effective to determine the thermoelectric power of materials under pressure. [ABSTRACT FROM AUTHOR]

The thermoelectric Hall effect is the generation of a transverse heat current upon applying an electric field in the presence of a magnetic field. Here, we demonstrate that the thermoelectric Hall conductivity αxy in the three-dimensional Dirac semimetal ZrTe5 acquires a robust plateau in the extreme quantum limit of magnetic field. The plateau value is independent of the field strength, disorder strength, carrier concentration, or carrier sign. We explain this plateau theoretically and show that it is a unique signature of three-dimensional Dirac or Weyl electrons in the extreme quantum limit. We further find that other thermoelectric coefficients, such as the thermopower and Nernst coefficient, are greatly enhanced over their zero-field values even at relatively low fields. A sufficiently strong magnetic field drives an electron system into the so-called extreme quantum limit. Zhang et al. demonstrate that in this regime, a Dirac semimetal acquires a robust plateau in the thermoelectric Hall conductivity, with a value independent of magnetic field or electron concentration. [ABSTRACT FROM AUTHOR]

The emerging phase change materials (PCMs) have attracted much attention due to their unique properties and applications. However, the optical properties of PCM at high pressures have not been well explored. In this work, the microstructure and optical properties of GeTe and Sn-substituted GeTe at high pressures up to 30 GPa have been systematically investigated. We find that the substitution of small amounts of Sn for Ge combined with the introduction of high pressure can induce an optical contrast of 117% in crystalline GeTe, which is even higher than the highest optical contrast reported so far (90%) caused by amorphous GeTe to crystalline GeTe. The pressure-induced contrast does not originate from any phase transition as previously, but from the combined effect of Peierls distortion elimination and Ge vacancy formation, which leads to an increase in carrier concentration. The relationship between pressure/atomic composition, Peierls distortion/vacancy formation, and optical contrast can be well explained by a combination of experiments and theoretical calculations. Therefore, this study reveals the effect of high pressure on the optical properties of PCMs and provides new ideas for the design of high-optical-contrast PCMs. [ABSTRACT FROM AUTHOR]

A periodic metagate is designed on top of a boron nitride-graphene heterostructure to modulate the local carrier density distribution on the monolayer graphene. This causes the bandgaps of graphene surface plasmon polaritons to emerge because of either the interaction between the plasmon modes, which are mediated by the varying local carrier densities, or their interaction with the metal gates. Using the example of a double-gate graphene device, we discuss the tunable band properties of graphene plasmons due to the competition between these two mechanisms. Because of this, a bandgap inversion, which results in a Zak phase switching, can be realized through electrostatic gating. Here we also show that an anisotropic plasmonic topological edge state exists at the interface between two graphene gratings of different Zak phases. While the orientation of the dipole moments can differentiate the band topologies of each graphene grating, the angle of radiation remains a tunable property. This may serve as a stepping stone toward active control of the band structures of surface plasmons for potential applications in optical communication, wave steering, or sensing. [ABSTRACT FROM AUTHOR]

Li and N co-doped InZnSnO (IZTOLiN) thin film transistors (TFTs) with a bottom-gate structure were fabricated. The IZTOLiN thin film was deposited on the p-Si/SiO2 substrate at room temperature by radio frequency magnetron sputtering. The optical transmittance and microstructure of the IZTOLiN thin film were examined. The IZTOLiN TFT shows excellent performance with saturation mobility (μSAT) of 38.9 cm2/V ⋅ s, threshold voltage (VTH) of 3.2 V, subthreshold swing (SS) of 0.6 V/decade, and current on/off ratio (ION/IOFF) of 3.5 × 109. The mobility of the aged IZTOLiN TFT decreased while the IOFF increased due to the increase in carrier concentration induced by H2O adsorption. The effect of active layer thickness on the electrical characteristics of the TFTs was investigated. With the IZTOLiN film thickness increased, the mobility increased first and then decreased while the SS degraded continuously. [ABSTRACT FROM AUTHOR]

At present the photoelectrochemical (PEC) water splitting achieves a very high efficiency, but the development of the efficient and inexpensive photoanode materials is still desired for practical application. Herein, we fabricate a composite photoanode consisting of TiO 2 nanotube arrays modified with polyoxometalate (POM) and Co 9 S 8 , in which POM aims to facilitate charge separation and Co 9 S 8 acts as good electron transport mediator. It is the first introduction of Co 9 S 8 into PEC water oxidation system. Although these three components are all non-precious inorganic materials, the photocurrent density of the TiO 2 /Co 9 S 8 /POM composite photoanode reaches up to 1.12 mA/cm 2 at 1.23 V vs RHE under simulated solar light illumination, which is among the highest PEC water oxidation photoanodes. Particularly, the TiO 2 /Co 9 S 8 /POM composite photoanode shows an 8.5-fold improvement in photocurrent density compared to the pristine TiO 2 nanotube array photoanode. The measurements of EIS and Mott-Schottky plots revealed that the TiO 2 /Co 9 S 8 /POM composite photoanode held the best efficiency of charge separation and transport at the interface as well as the highest carrier density. The aforementioned results demonstrate a feasible approach to improving the PEC water splitting efficiency by dual modification of TiO 2 nanotube arrays with low-cost materials. [ABSTRACT FROM AUTHOR]

Highlights: [•] Hole concentration of p-GaN was enhanced by multi-step activation process. [•] The O2 plasma treatment is attributed to the enhanced hole concentration of p-GaN. [•] PL peak intensity was also enhanced by MS activation process. [Copyright &y& Elsevier]

The effective electron mobility in long-channel silicon-on-insulator junctionless multigate metal-oxide-semiconductor transistors is experimentally studied. It is found that the mobility in heavily doped narrow nanowire (NW) devices at low to moderately high carrier densities significantly exceeds that in wide (planar) devices with the same silicon thickness and doping and, in a certain range of carrier densities, it exceeds the mobility in bulk silicon with the same doping concentration. This effect increases when decreasing the NW width. The possible origins of this effect are discussed. These results are extremely encouraging for the development of junctionless NW transistors. [ABSTRACT FROM AUTHOR]

The n‐type MNiSn (M = Ti, Zr, or Hf) half‐Heusler compounds are reported as promising medium‐ and high‐temperature thermoelectric materials; however, their p‐type counterparts have suffered from poor performance due to the in‐gap state caused by Ni occupying the tetrahedral interstitials. Inspired by recent findings that thermoelectric performance can be enhanced without substantially increasing compositional or structural complexity, the study attempts to manipulate the Ni interstitial defects by altering the stoichiometric composition. The results show that when HfNiSn is prepared by a non‐equilibrium method, the intrinsic Ni defects are effectively suppressed by simply reducing the nominal Ni content. The suppression of Ni defects not only leads to a larger bandgap, but also attenuates carrier scattering to achieve higher mobility. After further optimization of the carrier concentration, the p‐type HfNi0.85Co0.05Sn achieves a maximum power factor of 3100 µW m−1 K−2 at 773 K and a peak zT of ≈0.7 at 973 K, both of which are superior to that of the state‐of‐the‐art p‐type MNiSn. The results demonstrate that the off‐stoichiometric ratio is effective in decoupling electron‐phonon transports of thermoelectric materials with massive intrinsic defects, and also contribute to understanding the role of defect modulation in optimizing thermoelectric properties. [ABSTRACT FROM AUTHOR]

Liquid‐like materials are one family of promising thermoelectric materials discovered in the past years due to their advantanges of ultrahigh thermoelectric figure of merit (zT), low cost, and environmental friendliness. However, their practial applications are greatly limited by the low service stability from the Cu/Ag metal deposition under large current and/or temperature gradient. Both high zT for high efficiency and large critical voltage for good stability are required for liquid‐like materials, but they are usually strongly correlated and hard to be tuned individually. Herein, based on the thermodynamic analysis, it is shown that such a correlation can be decoupled through doping immobile ions into the liquid‐like sublattice. Taking Cu2−δS as an example, doping immobile Fe ions in Cu1.90S scarcely degrades the initial large critical voltage, but significantly enhances the zT to 1.5 at 1000 K by tuning the carrier concentration to the optimal range. Combining the low‐cost and environmentally friendly features, these Fe‐doped Cu2−δS‐based compounds show great potential in civil applications. This study sheds light on the realization of both good stability and high performance for many other liquid‐like thermoelectric materials that have not been considered for real applications before. [ABSTRACT FROM AUTHOR]

Plasmonic ZrNx thin films were prepared by ion beam assisted deposition (IBAD). The effects of the assisting ion current (Ia), assisting ion energy (Ea) and the partial flow rate ratio of N2/Ar (r) on the structure and dielectric properties of the films were investigated. The results show that all the films are fcc-structured, and the IBAD films exhibit a preferred fcc-(1 1 1) orientation. Nitrogen content of the films can be improved by higher Ea and r, and reduced by higher Ia. Higher Ia, Ea or r can reduce the crossover frequency at which the films turn from dielectric to metallic phase, and reduce the loss function of the films. Moreover, the plasmonic quality factor can also be modulated by these parameters. The main mechanism of the modulation is the variation of the carrier concentration in the films. Our study demonstrates that the IBAD-ZrNx thin films have considerable plasmonic performances, and their dielectric and plasmonic properties can be modulated from visible to near infrared region by assisting ion beam. [ABSTRACT FROM AUTHOR]

Much progress on highly efficient thermoelectric materials have been made in the p-type PbTe. However, the n-type PbTe only shows a relatively low figure of merit ZT and conversion efficiency η, which is urgently required to be strengthened and compatible with p-type counterpart from the viewpoint of large-scale applications. Here, we report that n-type Sb-doped PbTe alloys can directly improve the power factor owing to the optimized carrier concentration. Moreover, the unexpected synergistic effect, deriving from alloying and nano-precipitates scattering due to Sb doping, triggers a dramatic reduction of lattice thermal conductivity. Consequently, a remarkable ZT of ~ 1.3 at 673 K in n-type Pb0.98Sb0.02Te and the average ZTave of ~ 0.83 with the calculated conversion efficiency η of ~ 12.3% in a wide temperature range from 323 to 823 Κ are achieved. The present findings demonstrate the excellent potential in n-type Sb-doped PbTe thermoelectric materials through a synergetic carrier tuning and multiple phonon scattering strategy, which provides a new avenue for exploring high-performance thermoelectric materials in n-type PbTe and/or other materials. [ABSTRACT FROM AUTHOR]

Mg 2 (Sn,Si) films with different Si content were prepared by magnetron sputtering. The phase composition, surface and cross-sectional morphology, chemical composition and element distribution, carrier concentration, carrier mobility, electrical conductivity, Seebeck coefficient and power factor of the deposited Mg–Sn–Si films were studied. The results show that the deposited films are composed of Mg 2 (Sn,Si) solid solution phase and a small amount of metal Mg phase. The room temperature carrier concentration decreases and mobility increases with increasing Si content in deposited Mg–Sn–Si films, respectively. The room temperature electrical conductivity and Seebeck coefficient decreases and increases with increasing Si content, respectively. The deposited Mg 2 (Sn,Si) films with moderate Si content possess the maximum power factor value of 2.76 mW m−1 K−2 at 303 °C and its room temperature figure of merit reaches the highest value of 0.44. The thermal conductivity decreases with increasing Si content, indicating that the lattice distortion caused by Si doping can reduce the thermal conductivity of the deposited films. • The Mg 2 (Sn,Si) solid solution films with different Si content were prepared by magnetron sputtering. • The carrier concentration decreases and mobility increases with increasing Si content. • The Mg 2 (Sn,Si) films with moderate Si content possess the maximum PF value of 2.76 mW m−1 K−2 at 303 °C. • The lattice distortion caused by Si doping can reduce the thermal conductivity of the deposited films. [ABSTRACT FROM AUTHOR]

• SERS performance of the ion-beam-deposited TiN x films substrates was investigated. • The SERS performance is sensitive to the thickness of TiN x layer. • The ion-bombardment contributes to the SERS effect of the TiN x /Si substrate. • Suitable ion current and energy can improve the SERS performance to several times. Titanium nitride ( TiN x ) thin films were fabricated on silicon substrates by ion beam deposition. The surface enhanced Raman scattering (SERS) effect of the TiN x /Si substrates was studied with Rhodamine 6G as probe molecule. The results show that TiN x thin films can enhance the Raman signal, and the film with suitable thickness can significantly improve the SERS performance. For the 30 nm thick TiN x thin films the enhancement factor is up to 6.6 × 10 4 . The enhancement factor can be further improved several times by assisting ions. The main role of the assisting ions is to enhance the intensity and density of hot spots through the modification of surface morphology and plasmons. The study implies that high carrier concentration, and suitable size and high density of the grains and gaps are important for improving SERS performance. This work indicates the promising future of TiN x and assisting ions in the development of SERS active templates. [ABSTRACT FROM AUTHOR]

Dual rare earth (La/Ce) doped In 2 O 3 hierarchical microstructures are prepared by a hydrothermal method followed by calcination. Various combination amounts of La and Ce are systematically investigated via a climbing method to determine an optimized co-doping sample. Characterization results indicate that doping enables to distort crystal structure, leading to hierarchical morphology with large surface area, abundant surface defects and oxygen vacancy. Gas sensing tests reveal that co-doping into In 2 O 3 significantly improves the sensing performance towards n -butanol. The La 1 Ce 4.5 -In 2 O 3 sample has the highest sensing response (143) towards 100 ppm n -butanol at the optimized temperature of 280 °C, which is 8.0, 4.3 and 1.4 times higher than that of the pristine In 2 O 3 , La 1 -In 2 O 3 and Ce 4.5 -In 2 O 3 , respectively. To deeply understand the enhanced sensing mechanism, electrochemical experiments are conducted. The high sensing performance of La 1 Ce 4.5 -In 2 O 3 can be attributed to: (1) its optimized band structure, (2) large carrier density, (3) low charge transfer resistance, and (4) strong redox activity on the surface of materials. [Display omitted] • La, Ce co-doped In 2 O 3 microflowers are prepared and the combination of La and Ce are optimized by climbing method. • La 1 Ce 4.5 -In 2 O 3 sample exhibits the highest response (143) to 100 ppm n-butanol at 280 °C. • Enhanced performance is due to adjustable electrochemical and semiconducting properties by co-doping La and Ce. [ABSTRACT FROM AUTHOR]

Abstract The reductive dissolution of pyrolusite in simulated Acidithiobacillus ferrooxidans bio-leaching medium was investigated. This study was performed in three stages. First, the advantageous electrochemical test conditions, parallel to the optimal bio-leaching conditions and adopting the Mn reduction rate, were determined by imitated electrolysis. The facilitation of A. ferrooxidans on MnO 2 reduction is sensitive to pH and Fe(III) concentration. Second, electrochemical tests revealed that the reductive dissolution of manganese dioxide incorporated two single electron and proton steps-the first exchange of MnO 2 to MnO·OH, and then conversion to Mn(OH) 2 for diffusion. The results of transient and steady electrochemical measurements indicated that the first electron-transfer significantly affects the rate controlling step of Mn-leaching in control(9K) medium, while using A. ferrooxidans and Fe(III) in the solution tends to enable the leaching rate to be controlled by the latter electron transfer step. Third, the analysis of semiconductor and carrier properties of passive films of pyrolusite formed in the different solutions, illustrated that the reductive dissolution of manganese dioxide tends to depend on the movement of the holes. The first electron preferentially reacts with the shallow energy level of the O-vacancy to form MnO 2 ·-, which then absorbs H+ to become MnO·OH. The second electron participates in the transformation of MnO·OH to (MnOH)(OH) and then to Mn(OH) 2. A. ferrooxidans increases the carrier densities of the passivating film accelerating electron and proton transfer and Fe(III) primarily influences the shallow donor density of oxygen during the first electron-exchange. Additionally, the synergistic effect of A. ferrooxidans and Fe(III) on manganese dioxide ore reductive leaching is confirmed. [ABSTRACT FROM AUTHOR]

The Mg 2 Sn/Mg multilayer films with different nano-sized modulation period were successfully prepared on single crystalline Si substrate with 500 ​nm thickness SiO 2 layer by alternately sputtering using high pure metal Mg target and Mg–Sn alloy target. The chemical composition, surface and cross-sectional morphology, phase composition, carrier transport process and thermoelectric properties of deposited films were deeply investigated. The results show that the deposited films possess obvious layered structure, which is composed of metal Mg layer and antifluorite cubic Mg 2 Sn layer. The atom ratio [Mg]/[Sn]<2.0 in Mg 2 Sn layer between metal Mg layers and deposited films are p-typed semiconductor due to the existence of Mg vacancy in Mg 2 Sn lattice. The carrier concentration, mobility and thermal conductivity at room temperature decrease with reducing the modulation period of the multilayer films due to scattering of layer interface, at which depletion layer and built-in electric field form, impeding motion of the carriers. The electrical conductivity slightly decrease, but the Seebeck coefficient, power factor and figure of merit (ZT) greatly increase with reducing modulation period due to the scattering of the carriers. The ZT value of the film with the smallest modulation period of 171 ​nm reaches 0.51. The introduction of the layer interface greatly strengthens the carrier scattering process and improves the thermoelectric properties of the deposited films. This work demonstrates that introduction of heterogeneous interfaces composed of the same elements into films can effectively improve its thermoelectric properties. [Display omitted] • The Mg 2 Sn/Mg multilayer films with nano-sized period were prepared by alternately sputtering. • The carrier concentration and mobility at room temperature reduce by layer interface scattering. • The Seebeck coefficient and figure of merit (ZT) greatly increase by more layer interface. • The introduction of the layer interface greatly improves the thermoelectric properties of films. [ABSTRACT FROM AUTHOR]

Cesium lead bromide (CsPbBr 3) perovskite micro/nanostructures have potential applications in miniaturized integrated light sources due to their confined modal volume and high luminous efficiency. In this work, we synthesized CsPbBr 3 nanoplates with regular square shapes and smooth surface by the chemical vapor deposition method. The temperature-dependent and excitation power-dependent photoluminescence spectra reveal the excitonic photoluminescence properties. The whispering gallery mode (WGM)-like lasing in CsPbBr 3 nanoplates was observed at room temperature. We systematically investigated the pump fluence-dependent multi-mode and single-mode lasing actions in square microcavities. The blueshift of individual lasing modes can be attributed to the variation of refractive index resulting from the formation of the electron-hole plasma (EHP) state under highly injected carrier density. The results reveal the dependence of emission properties on excitation intensity, providing further understanding of the carrier-induced mode shift mechanism in the WGM-like lead halide perovskite microcavities. • The excitons in CsPbBr 3 nanoplates undergo a detrapping process with increasing temperature. • The electron-hole plasma lasing mechanism in square CsPbBr 3 nanoplates was revealed. • The refractive index-dependent lasing mode shift behavior was demonstrated by simulation results. [ABSTRACT FROM AUTHOR]

[Display omitted] Lead-free inorganic Cs 2 AgBiBr 6 double perovskites have emerged as promising materials in perovskite solar cells (PSCs) to tackle the inferior stability and toxicity issues of organic–inorganic hybrid PSCs. However, the power conversion efficiencies (PCEs) of Cs 2 AgBiBr 6 solar cells are remarkably restricted by the intrinsic and extrinsic defects of Cs 2 AgBiBr 6 films. More specifically, the fast crystallization process in the formation of Cs 2 AgBiBr 6 films strongly prevents the homogeneous growth of perovskite crystals, leading to inferior Cs 2 AgBiBr 6 film quality. This work introduces a facile strategy to retard the crystallization of Cs 2 AgBiBr 6 perovskites by introducing Lewis base additives into the precursor solution. The incorporation of a strongly coordinated thiourea additive with a sulfur donor leads to the generation of a Lewis acid base adduct, which retards the crystallization process for Cs 2 AgBiBr 6 crystals, improves the quality of the Cs 2 AgBiBr 6 film, decreases the defect density and inhibits charge carrier recombination. After optimization, the cell delivers a superior PCE of 3.07%, surpassing that reported for most Cs 2 AgBiBr 6 -based solar cells in the literature, and exhibits outstanding stability with a PCE retention rate of 95% after 20 days of storage in air. This work provides an effective strategy for further improvements in the performance of inorganic lead-free Cs 2 AgBiBr 6 -based photovoltaic cells. [ABSTRACT FROM AUTHOR]

The misfit layer compound (SnS)1.2(TiS2)2 is a promising low-cost thermoelectric material because of its low thermal conductivity derived from the superlattice-like structure. However, the strong covalent bonds within each constituent layer highly localize the electrons thereby it is highly challenging to optimize the power factor by doping or alloying. Here, we show that Bi doping at the Sn site markedly breaks the covalent bonds networks and highly delocalizes the electrons. This results in a high charge carrier concentration and enhanced power factor throughout the whole temperature range. It is highly remarkable that Bi doping also significantly reduces the thermal conductivity by suppressing the heat conduction carried by phonons, indicating that it independently modulates phonon and charge transport properties. These effects collectively give rise to a maximum ZT of 0.3 at 720 K. In addition, we apply the single Kane band model and the Debyeâ€"Callaway model to clarify the electron and phonon transport mechanisms in the misfit layer compound (SnS)1.2(TiS2)2. [ABSTRACT FROM AUTHOR]

The radiation detection performance of CZT epitaxial single crystal grown by the Close Space Sublimation (CSS) method is hindered by inherent defects. However, significant improvement in this work is achieved through annealing in a Te 2 atmosphere. The saturation channel value of the total energy peak of the detector for 241Am α-particles has shown a substantial increase from 1900 to 6000, resulting in a notable enhancement of the carrier collection efficiency. After annealing, the detector's energy resolution to 241Am gamma-rays can reach 8.3%, representing the highest energy resolution achieved by CSS growth of CZT materials. This remarkable achievement holds great promise for its potential application in the field of low-energy detection. Analysis of the laser-beam-induced current (LBIC) curve results reveals that the surface recombination of the detector is more pronounced prior to annealing, adversely affecting the transport process of photogenerated carriers. The low-temperature photoluminescence (PL) results and I–V curve demonstrate a significant compensation effect on the shallow acceptor level V Cd after annealing, leading to a reduced concentration of free carriers and subsequently leading to lower leakage current and improved signal-to-noise ratio for the detector. The concurrent reduction in leakage current and surface recombination contributes collectively to improving the radiation detection performance of the CZT detector. These findings underscore the importance of annealing in a Te 2 atmosphere as a viable method for mitigating defects and optimizing the performance of CZT epitaxial single crystals, showcasing the potential for broader applications in the field of low-energy detection. • The leakage current is reduced from 1.3 nA to 0.59 nA under the applied bias voltage of 0.5 V, which makes the detector obtain a good signal-to-noise ratio. • The surface recombination rate decreased from 13.78 × 106 cm s−1 to 3.82 × 105 cm s−1, significantly improving the carrier collection efficiency. • The energy resolution to 241Am@59.5 KeV gamma-rays of the detector reached 8.3% for the first time, which is expected to be applied in the field of low energy detection. [ABSTRACT FROM AUTHOR]