Quasi one-dimensional polycrystalline samples of Ba_(3)Hf(Se_(1-x)Te_(x))_(5)(x=0-1)are synthesized under hightemperature and high-pressure conditions.Using the powder x-ray diffraction technique and first-principles ...Quasi one-dimensional polycrystalline samples of Ba_(3)Hf(Se_(1-x)Te_(x))_(5)(x=0-1)are synthesized under hightemperature and high-pressure conditions.Using the powder x-ray diffraction technique and first-principles calculations,Ba_(3)HfSe_(5)is identified as having a hexagonal structure with a space group of P63/mcm(193)and lattice constants of a=9.5756(1)A°,c=6.3802(7)A°.The structure is composed of Hf(Se1)6 chains and Se_(2)linear chains extending along the c-axis.As the doping content of Te increases,the lattice expands and leads to 5.8%and 7.3%increases of the a and c values and a 20.1%increase of the unit cell volume of Ba_(3)HfTe_(5)compared to Ba_(3)HfSe_(5).The detailed structural refinements show that the Hf vacancies decrease gradually as Te doping increases in the Ba_(3)Hf(Se_(1-x)Te_(x))_(5)(x=0-1)materials,which leads to a decrease of electronic localization.In addition,the lower electronegativity of Te and the more extended orbitals with respect to Se contribute to orbital overlap between the inter chains.All these dominate the enhanced electron hopping,leading to a reduction of the bandgap from 1.95 eV to 0.23 eV for Ba_(3)Hf(Se_(1-x)Te_(x))_(5)(x=0-1)materials as the Ba_(3)HfSe_(5)evolves to Ba_(3)HfTe_(5).展开更多
We report a GaInP/GaAs tandem solar cell with a novel GaAs tunnel junction（TJ） with using tellurium（Te） and magnesium（Mg） as n- and p-type dopants via dual-filament low temperature effusion cells grown by molecu...We report a GaInP/GaAs tandem solar cell with a novel GaAs tunnel junction（TJ） with using tellurium（Te） and magnesium（Mg） as n- and p-type dopants via dual-filament low temperature effusion cells grown by molecular beam epitaxy（MBE） at low temperature. The test Te/Mg-doped GaAs TJ shows a peak current density of 21 A/cm2. The tandem solar cell by the Te/Mg TJ shows a short-circuit current density of 12 m A/cm2, but a low open-circuit voltage range of1.4 V^1.71 V under AM1.5 illumination. The secondary ion mass spectroscopy（SIMS） analysis reveals that the Te doping is unexpectedly high and its doping profile extends to the Mg doping region, thus possibly resulting in a less abrupt junction with no tunneling carriers effectively. Furthermore, the tunneling interface shifts from the intended Ga As n＋＋/p＋＋junction to the AlGaInP/GaAs junction with a higher bandgap AlGaInP tunneling layers, thereby reducing the tunneling peak. The Te concentration of ~ 2.5 × 1020 in GaAs could cause a lattice strain of 10-3 in magnitude and thus a surface roughening,which also negatively influences the subsequent growth of the top subcell and the GaAs contacting layers. The doping features of Te and Mg are discussed to understand the photovoltaic response of the studied tandem cell.展开更多
In this study,large-scale Te-doped polycrystalline SnSe nanopowders were synthesized by a facile hydrothermal approach and the effect of Te doping on the thermoelectric properties of SnSe was fully investigated.It is ...In this study,large-scale Te-doped polycrystalline SnSe nanopowders were synthesized by a facile hydrothermal approach and the effect of Te doping on the thermoelectric properties of SnSe was fully investigated.It is found that the carrier concentration increases due to the reduction of band gap by alloying with Te,which contributes to significant enhancement of electrical conductivity especially at room temperature.Combined with the moderated Seebeck coefficient,a high power factor of 4.59μW cm 1 K 2 is obtained at 773 K.Furthermore,the lattice the rmal conductivity is greatly reduced upon Te substitution owing to the atomic point defect scattering.Benefiting from the synergistically optimized both electrical-and thermal-transport properties by Te-doping,thermoelectric performance of polycrystalline SnSe is enhanced in the whole temperature range with a maximum ZT of-0.79 at a relatively low temperature(773 K) for SnSe0.85Te0.15.This study provides a low-cost and simple lowtemperature method to mass production of SnSe with high thermoelectric performance for practical applications.展开更多
The multiple-state storage capability of phase change memory （PCM） is confirmed by using stacked chalcogenide films as the storage medium. The current-voltage characteristics and the resistance-current characteristi...The multiple-state storage capability of phase change memory （PCM） is confirmed by using stacked chalcogenide films as the storage medium. The current-voltage characteristics and the resistance-current characteristics of the PCM clearly indicate that four states can be stored in this stacked film structure. Qualitative analysis indicates that the multiple-state storage capability of this stacked film structure is due to successive crystallizations in different Si-Sb-Te layers triggered by different amplitude currents.展开更多
Doped with Sb and Te, Mg2Si based compounds were prepared respectively by solid state reaction at 823 K for 8 h. Effects of dopants of Sb and Te on the structure and thermoelectric properties of the compounds were inv...Doped with Sb and Te, Mg2Si based compounds were prepared respectively by solid state reaction at 823 K for 8 h. Effects of dopants of Sb and Te on the structure and thermoelectric properties of the compounds were investigated. By calculating the values of the electrical conductivity for Sb-doped sample, the mechanism of electric conduction at 625 K is different. The figure of merit for sample doped with 0.4 wt% Te at500K is 2.4 × 10-3W/mK2,and it reaches 3. 3 ×10-3 W/mK2 at 650K for the sample doped with 0. 5wt% Sb. The values are more than 1.4 times and 2.3 times of the pure Mg2 Si sample.展开更多
Appropriate non-metallic element doping is promising to improve the intrinsic electrocatalytic oxygen reduction reaction(ORR)performance of nitrogen-doped carbon candidates,yet challenges still remain to rationally de...Appropriate non-metallic element doping is promising to improve the intrinsic electrocatalytic oxygen reduction reaction(ORR)performance of nitrogen-doped carbon candidates,yet challenges still remain to rationally design of the catalyst configuration with kinetically favorable state.Herein,we propose the metalloid element to regulate the local electronic environment,and a novel metal-free electrocatalyst,namely,atomically dispersed Te-N_(2) on nitrogen-doped carbon frameworks was developed.Characterization and theoretical analyses demonstrate that the heteroatoms tellurium integrated with nitrogen-doped carbon substrate forms a Te-N covalent coordination as the active center that empowers both improved ORR kinetics and structural stability.As expected,the optimized composite of Te-N-C 900 delivers considerable electrocatalytic ORR activity in alkaline media(E_(1/2)=0.871 V,0.1 M KOH),along with encouraging durability(over 10,000 cycles with 13 mV decay),which is also responsible for Zn-air batteries operating with high uplifting peak power density and long lifespan.As a proof-of-concept,this work elucidates the key influence of heteroatom interaction of metalloid element,achieves the synthesis of Te-N_(2) metal-free ORR catalysts,and provides guidance for the development of high-performance metal-free ORR catalysts.展开更多
Cu_(1.8)S has been considered as a potential thermoelectric(TE)material for its stable electrical and thermal properties,environmental benignity,and low cost.Herein,the TE properties of nanostructured Cu_(1.8)S_(1-x)T...Cu_(1.8)S has been considered as a potential thermoelectric(TE)material for its stable electrical and thermal properties,environmental benignity,and low cost.Herein,the TE properties of nanostructured Cu_(1.8)S_(1-x)Te_(x)(0≤x≤0.2)bulks fabricated by a facile process combining mechanical alloying(MA)and room-temperature high-pressure sintering(RT-HPS)technique were optimized via eliminating the volatilization of S element and suppressing grain growth.Experimentally,a single phase of Cu_(1.8)S was obtained at x=0,and a second Cu_(1.96)S phase formed in all Cu_(1.8)S_(1-x)Te_(x) samples when 0.05≤x≤0.125.With further increasing x to 0.15≤x≤0.2,the Cu_(2-z)Te phase was detected and the samples consisted of Cu_(1.8)S,Cu_(1.96)S,and Cu_(2-z)Te phases.Benefiting from a modified band structure and the coexisted phases of Cu_(1.96)S and Cu_(2-z)Te,the power factor is enhanced in all Cu_(1.8)S_(1-x)Te_(x)(0.05≤x≤0.2)alloys.Combining with a drastic decrease in the thermal conductivity due to the strengthened phonon scatterings from multiscale defects introduced by Te doping and nano-grain boundaries,a maximum figure of merit(ZT)of 0.352 is reached at 623 K for Cu_(1.8)S_(0.875)Te_(0.125),which is 171%higher than that of Cu_(1.8)S(0.130).The study demonstrates that doping Te is an effective strategy to improve the TE performance of Cu_(1.8)S based materials and the proposed facile method combing MA and RT-HPS is a potential way to fabricate nanostructured bulks.展开更多
2μm InGaSb/AlGaAsSb strained quantum wells and a tellurium-doped GaSb buffer layer were grown by molecular beam epitaxy（MBE）.The growth parameters of strained quantum wells were optimized by AFM, XRD and PL at 77 K...2μm InGaSb/AlGaAsSb strained quantum wells and a tellurium-doped GaSb buffer layer were grown by molecular beam epitaxy（MBE）.The growth parameters of strained quantum wells were optimized by AFM, XRD and PL at 77 K.The optimal growth temperature of quantum wells is 440℃.The PL peak wavelength of quantum wells at 300 K is 1.98μm,and the FWHM is 115 nm.Tellurium-doped GaSb buffer layers were optimized by Hall measurement.The optimal doping concentration is 1.127×10^（18） cm^（-3） and the resistivity is 5.295×10^（-3）Ω·cm.展开更多
基金supported by the National Key R&D Program of China(Grant Nos.2023YFA1406001 and 2024YFA1408004)the National Natural Science Foundation of China(Grant Nos.12104488 and 12474097).
文摘Quasi one-dimensional polycrystalline samples of Ba_(3)Hf(Se_(1-x)Te_(x))_(5)(x=0-1)are synthesized under hightemperature and high-pressure conditions.Using the powder x-ray diffraction technique and first-principles calculations,Ba_(3)HfSe_(5)is identified as having a hexagonal structure with a space group of P63/mcm(193)and lattice constants of a=9.5756(1)A°,c=6.3802(7)A°.The structure is composed of Hf(Se1)6 chains and Se_(2)linear chains extending along the c-axis.As the doping content of Te increases,the lattice expands and leads to 5.8%and 7.3%increases of the a and c values and a 20.1%increase of the unit cell volume of Ba_(3)HfTe_(5)compared to Ba_(3)HfSe_(5).The detailed structural refinements show that the Hf vacancies decrease gradually as Te doping increases in the Ba_(3)Hf(Se_(1-x)Te_(x))_(5)(x=0-1)materials,which leads to a decrease of electronic localization.In addition,the lower electronegativity of Te and the more extended orbitals with respect to Se contribute to orbital overlap between the inter chains.All these dominate the enhanced electron hopping,leading to a reduction of the bandgap from 1.95 eV to 0.23 eV for Ba_(3)Hf(Se_(1-x)Te_(x))_(5)(x=0-1)materials as the Ba_(3)HfSe_(5)evolves to Ba_(3)HfTe_(5).
基金Project supported by the SINANO-SONY Joint Program(Grant No.Y1AAQ11001)the National Natural Science Foundation of China(Grant No.61274134)+1 种基金the USCB Start-up Program(Grant No.06105033)the International Cooperation Projects of Suzhou City,China(Grant No.SH201215)
文摘We report a GaInP/GaAs tandem solar cell with a novel GaAs tunnel junction（TJ） with using tellurium（Te） and magnesium（Mg） as n- and p-type dopants via dual-filament low temperature effusion cells grown by molecular beam epitaxy（MBE） at low temperature. The test Te/Mg-doped GaAs TJ shows a peak current density of 21 A/cm2. The tandem solar cell by the Te/Mg TJ shows a short-circuit current density of 12 m A/cm2, but a low open-circuit voltage range of1.4 V^1.71 V under AM1.5 illumination. The secondary ion mass spectroscopy（SIMS） analysis reveals that the Te doping is unexpectedly high and its doping profile extends to the Mg doping region, thus possibly resulting in a less abrupt junction with no tunneling carriers effectively. Furthermore, the tunneling interface shifts from the intended Ga As n＋＋/p＋＋junction to the AlGaInP/GaAs junction with a higher bandgap AlGaInP tunneling layers, thereby reducing the tunneling peak. The Te concentration of ~ 2.5 × 1020 in GaAs could cause a lattice strain of 10-3 in magnitude and thus a surface roughening,which also negatively influences the subsequent growth of the top subcell and the GaAs contacting layers. The doping features of Te and Mg are discussed to understand the photovoltaic response of the studied tandem cell.
基金funded by the Fundamental Research Funds for the Central Universities (No.2232020A-02)National Natural Science Foundation of China (Nos.51774096,51871053,51902333)+3 种基金Shanghai Committee of Science and Technology (No.18JC1411200)Program for Innovative Research Team in University of Ministry of Education of China (No.IRT16R13)financial support sponsored by Shanghai Sailing Program (No. 19YF1454000)Key Research Program of Frontier Sciences,CAS (No.ZDBS-LY-JSC037)。
文摘In this study,large-scale Te-doped polycrystalline SnSe nanopowders were synthesized by a facile hydrothermal approach and the effect of Te doping on the thermoelectric properties of SnSe was fully investigated.It is found that the carrier concentration increases due to the reduction of band gap by alloying with Te,which contributes to significant enhancement of electrical conductivity especially at room temperature.Combined with the moderated Seebeck coefficient,a high power factor of 4.59μW cm 1 K 2 is obtained at 773 K.Furthermore,the lattice the rmal conductivity is greatly reduced upon Te substitution owing to the atomic point defect scattering.Benefiting from the synergistically optimized both electrical-and thermal-transport properties by Te-doping,thermoelectric performance of polycrystalline SnSe is enhanced in the whole temperature range with a maximum ZT of-0.79 at a relatively low temperature(773 K) for SnSe0.85Te0.15.This study provides a low-cost and simple lowtemperature method to mass production of SnSe with high thermoelectric performance for practical applications.
文摘The multiple-state storage capability of phase change memory （PCM） is confirmed by using stacked chalcogenide films as the storage medium. The current-voltage characteristics and the resistance-current characteristics of the PCM clearly indicate that four states can be stored in this stacked film structure. Qualitative analysis indicates that the multiple-state storage capability of this stacked film structure is due to successive crystallizations in different Si-Sb-Te layers triggered by different amplitude currents.
文摘Doped with Sb and Te, Mg2Si based compounds were prepared respectively by solid state reaction at 823 K for 8 h. Effects of dopants of Sb and Te on the structure and thermoelectric properties of the compounds were investigated. By calculating the values of the electrical conductivity for Sb-doped sample, the mechanism of electric conduction at 625 K is different. The figure of merit for sample doped with 0.4 wt% Te at500K is 2.4 × 10-3W/mK2,and it reaches 3. 3 ×10-3 W/mK2 at 650K for the sample doped with 0. 5wt% Sb. The values are more than 1.4 times and 2.3 times of the pure Mg2 Si sample.
基金supported by the National Natural Science Foundation of China(No.22278097)the Postdoctoral fellowship of Heilongjiang Province(No.LBH-Z23156)+3 种基金the Postdoctoral Fellowship Program of CPSF(No.GZC20233449)the Shandong Provincial Natural Science Foundation(No.ZR2024QB383)the Natural Science Foundation of Jiangsu Province(No.BK20230635)the Natural Science Foundation of the Jiangsu Higher Education Institutions of China(No.23KJB150002).
文摘Appropriate non-metallic element doping is promising to improve the intrinsic electrocatalytic oxygen reduction reaction(ORR)performance of nitrogen-doped carbon candidates,yet challenges still remain to rationally design of the catalyst configuration with kinetically favorable state.Herein,we propose the metalloid element to regulate the local electronic environment,and a novel metal-free electrocatalyst,namely,atomically dispersed Te-N_(2) on nitrogen-doped carbon frameworks was developed.Characterization and theoretical analyses demonstrate that the heteroatoms tellurium integrated with nitrogen-doped carbon substrate forms a Te-N covalent coordination as the active center that empowers both improved ORR kinetics and structural stability.As expected,the optimized composite of Te-N-C 900 delivers considerable electrocatalytic ORR activity in alkaline media(E_(1/2)=0.871 V,0.1 M KOH),along with encouraging durability(over 10,000 cycles with 13 mV decay),which is also responsible for Zn-air batteries operating with high uplifting peak power density and long lifespan.As a proof-of-concept,this work elucidates the key influence of heteroatom interaction of metalloid element,achieves the synthesis of Te-N_(2) metal-free ORR catalysts,and provides guidance for the development of high-performance metal-free ORR catalysts.
基金supported by the National Key R&D Program of China(Grant No.2018YFB0703600)the National Natural Science Foundation of China(Grant No.11474176).
文摘Cu_(1.8)S has been considered as a potential thermoelectric(TE)material for its stable electrical and thermal properties,environmental benignity,and low cost.Herein,the TE properties of nanostructured Cu_(1.8)S_(1-x)Te_(x)(0≤x≤0.2)bulks fabricated by a facile process combining mechanical alloying(MA)and room-temperature high-pressure sintering(RT-HPS)technique were optimized via eliminating the volatilization of S element and suppressing grain growth.Experimentally,a single phase of Cu_(1.8)S was obtained at x=0,and a second Cu_(1.96)S phase formed in all Cu_(1.8)S_(1-x)Te_(x) samples when 0.05≤x≤0.125.With further increasing x to 0.15≤x≤0.2,the Cu_(2-z)Te phase was detected and the samples consisted of Cu_(1.8)S,Cu_(1.96)S,and Cu_(2-z)Te phases.Benefiting from a modified band structure and the coexisted phases of Cu_(1.96)S and Cu_(2-z)Te,the power factor is enhanced in all Cu_(1.8)S_(1-x)Te_(x)(0.05≤x≤0.2)alloys.Combining with a drastic decrease in the thermal conductivity due to the strengthened phonon scatterings from multiscale defects introduced by Te doping and nano-grain boundaries,a maximum figure of merit(ZT)of 0.352 is reached at 623 K for Cu_(1.8)S_(0.875)Te_(0.125),which is 171%higher than that of Cu_(1.8)S(0.130).The study demonstrates that doping Te is an effective strategy to improve the TE performance of Cu_(1.8)S based materials and the proposed facile method combing MA and RT-HPS is a potential way to fabricate nanostructured bulks.
基金Project supported by the Beijing Natural Science Foundation(No.4112058)the Science Foundation of the Chinese Academy of Sciences(No.CXJJ-11-M20)
文摘2μm InGaSb/AlGaAsSb strained quantum wells and a tellurium-doped GaSb buffer layer were grown by molecular beam epitaxy（MBE）.The growth parameters of strained quantum wells were optimized by AFM, XRD and PL at 77 K.The optimal growth temperature of quantum wells is 440℃.The PL peak wavelength of quantum wells at 300 K is 1.98μm,and the FWHM is 115 nm.Tellurium-doped GaSb buffer layers were optimized by Hall measurement.The optimal doping concentration is 1.127×10^（18） cm^（-3） and the resistivity is 5.295×10^（-3）Ω·cm.
