This paper introduces a high-precision bandgap reference(BGR)designed for battery management systems(BMS),fea-turing an ultra-low temperature coefficient(TC)and line sensitivity(LS).The BGR employs a current-mode sche...This paper introduces a high-precision bandgap reference(BGR)designed for battery management systems(BMS),fea-turing an ultra-low temperature coefficient(TC)and line sensitivity(LS).The BGR employs a current-mode scheme with chopped op-amps and internal clock generators to eliminate op-amp offset.A low dropout regulator(LDO)and a pre-regula-tor enhance output driving and LS,respectively.Curvature compensation enhances the TC by addressing higher-order nonlinear-ity.These approaches,effective near room temperature,employs trimming at both 20 and 60°C.When combined with fixed cur-vature correction currents,it achieves an ultra-low TC for each chip.Implemented in a CMOS 180 nm process,the BGR occu-pies 0.548 mm²and operates at 2.5 V with 84μA current draw from a 5 V supply.An average TC of 2.69 ppm/℃ with two-point trimming and 0.81 ppm/℃ with multi-point trimming are achieved over the temperature range of-40 to 125℃.It accommo-dates a load current of 1 mA and an LS of 42 ppm/V,making it suitable for precise BMS applications.展开更多
Although there are numerous optical spectroscopy techniques and methods that have been used to extract the fundamental bandgap of a semiconductor,most of them belong to one of these three approaches:(1)the excitonic a...Although there are numerous optical spectroscopy techniques and methods that have been used to extract the fundamental bandgap of a semiconductor,most of them belong to one of these three approaches:(1)the excitonic absorption,(2)modulation spectroscopy,and(3)the most widely used Tauc-plot.The excitonic absorption is based on a many-particle theory,which is physically the most correct approach,but requires more stringent crystalline quality and appropriate sample preparation and experimental implementation.The Tauc-plot is based on a single-particle theo⁃ry that neglects the many-electron effects.Modulation spectroscopy analyzes the spectroscopy features in the derivative spectrum,typically,of the reflectance and transmission under an external perturbation.Empirically,the bandgap ener⁃gy derived from the three approaches follow the order of E_(ex)>E_(MS)>E_(TP),where three transition energies are from exci⁃tonic absorption,modulation spectroscopy,and Tauc-plot,respectively.In principle,defining E_(g) as the single-elec⁃tron bandgap,we expect E_(g)>E_(ex),thus,E_(g)>E_(TP).In the literature,E_(TP) is often interpreted as E_(g),which is conceptual⁃ly problematic.However,in many cases,because the excitonic peaks are not readily identifiable,the inconsistency be⁃tween E_(g) and E_(TP) becomes invisible.In this brief review,real world examples are used(1)to illustrate how excitonic absorption features depend sensitively on the sample and measurement conditions;(2)to demonstrate the differences between E_(ex),E_(MS),and E_(TP) when they can be extracted simultaneously for one sample;and(3)to show how the popular⁃ly adopted Tauc-plot could lead to misleading results.Finally,it is pointed out that if the excitonic absorption is not ob⁃servable,the modulation spectroscopy can often yield a more useful and reasonable bandgap than Tauc-plot.展开更多
Low energy-storage density and inferior thermal stability are a long-term obstacle to the advancement of pulse power devices.Herein,these concerns are addressed by improving bandgap and fabricating polar nanoregions,a...Low energy-storage density and inferior thermal stability are a long-term obstacle to the advancement of pulse power devices.Herein,these concerns are addressed by improving bandgap and fabricating polar nanoregions,and the superior high efficiency of~86.7%,excellent thermal stability of~2%(31-160℃)and energy density of~6.8 J·cm^(-3)are achieved in Bi_(0.5)Na_(0.5)TiO_(3)-La_(0.1)Sr_(0.8)TiO_(3)-δ-NaNbO_(3)ceramics.The high breakdown strength(460 kV·cm^(-1))is ascribed to the broadened bandgap and refined grain.Slim ferroelectric loops originate from the construction of polar nanoregions(PNRs)in a pseudocubic matrix,and transmission electron microscope and piezoelectric force microscope measurements reveal the occurrence of PNRs.The phase-field stimulation and UV-Vis spectrophotometer measurement reveal that the increased grain boundary density and bandgap are beneficial for promoting breakdown strength.The strategy provides an efficient path to prepare Bi_(0.5)Na_(0.5)TiO_(3)La_(0.1)Sr_(0.8)TiO_(3)-δ-based ceramics with superior efficiency,high energy density and outstanding thermal stability.展开更多
Lead-tin(Pb-Sn)perovskites with an ideal bandgap of 1.34-1.40 eV show great promise in perovskite solar cells(PSCs).Recently,to address the environmental pollution and Sn^(2+)oxidation problems of dimethyl sulfoxide,m...Lead-tin(Pb-Sn)perovskites with an ideal bandgap of 1.34-1.40 eV show great promise in perovskite solar cells(PSCs).Recently,to address the environmental pollution and Sn^(2+)oxidation problems of dimethyl sulfoxide,methylammonium acetate(MAAc)ionic liquid has been developed as an alternative to fabricate ideal bandgap MAPb_(0.7)Sn_(0.3)I_(3)(1.36 eV)film via hot-casting in air.However,the spontaneous crystallization of Pb-Sn perovskite initiated by heat-induced supersaturation is fast and random,setting critical challenges in regulating crystal growth during the film-forming process.Herein,a lattice activation strategy is developed to control the crystallization dynamics of MAPb_(0.7)Sn_(0.3)I_(3)in MAAc to produce films with micrometer-sized grains in air.FA is shown to activate the crystal lattice that facilitates the formation of intermediates and balances the crystal growth of MAPb_(0.7)Sn_(0.3)I_(3),producing films with a grain size of 2.78±0.17μm.Furthermore,4-fluoro-phenethylammonium and phenethylammonium are adopted to passivate the defects in the film and promote the energy level alignment at the top interface,respectively.The optimized PSC device achieved an efficiency of 18.24%with a short-circuit current of 29.84 mA/cm^(2),which are both the highest values in 1.36 eV Pb-Sn PSCs to date.Notably,the unencapsulated devices show excellent storage and air stability under various conditions.展开更多
A novel elastic metamaterial is proposed with the aim of achieving lowfrequency broad bandgaps and bandgap regulation.The band structure of the proposed metamaterial is calculated based on the Floquet-Bloch theorem,an...A novel elastic metamaterial is proposed with the aim of achieving lowfrequency broad bandgaps and bandgap regulation.The band structure of the proposed metamaterial is calculated based on the Floquet-Bloch theorem,and the boundary modes of each bandgap are analyzed to understand the effects of each component of the unit cell on the bandgap formation.It is found that the metamaterials with a low elastic modulus of ligaments can generate flexural wave bandgaps below 300 Hz.Multi-frequency vibrations can be suppressed through the selective manipulation of bandgaps.The dual-graded design of metamaterials that can significantly improve the bandgap width is proposed based on parametric studies.A new way that can regulate the bandgap is revealed by studying the graded elastic modulus in the substrate.The results demonstrate that the nonlinear gradient of the elastic modulus in the substrate offers better bandgap performance.Based on these analyses,the proposed elastic metamaterials can pave the way for multi-frequency vibration control,low-frequency bandgap broadening,and bandgap tuning.展开更多
The bandgap is a key parameter for understanding and designing hybrid perovskite material properties,as well as developing photovoltaic devices.Traditional bandgap calculation methods like ultravioletvisible spectrosc...The bandgap is a key parameter for understanding and designing hybrid perovskite material properties,as well as developing photovoltaic devices.Traditional bandgap calculation methods like ultravioletvisible spectroscopy and first-principles calculations are time-and power-consuming,not to mention capturing bandgap change mechanisms for hybrid perovskite materials across a wide range of unknown space.In the present work,an artificial intelligence ensemble comprising two classifiers(with F1 scores of 0.9125 and 0.925)and a regressor(with mean squared error of 0.0014 eV)is constructed to achieve high-precision prediction of the bandgap.The bandgap perovskite dataset is established through highthroughput prediction of bandgaps by the ensemble.Based on the self-built dataset,partial dependence analysis(PDA)is developed to interpret the bandgap influential mechanism.Meanwhile,an interpretable mathematical model with an R^(2)of 0.8417 is generated using the genetic programming symbolic regression(GPSR)technique.The constructed PDA maps agree well with the Shapley Additive exPlanations,the GPSR model,and experiment verification.Through PDA,we reveal the boundary effect,the bowing effect,and their evolution trends with key descriptors.展开更多
Organic-inorganic hybrid solar cells consisting of organic conjugated materials and inorganic quantum dots(QDs)have been of great interest during the past two decades.However,it is still challenging to select desired ...Organic-inorganic hybrid solar cells consisting of organic conjugated materials and inorganic quantum dots(QDs)have been of great interest during the past two decades.However,it is still challenging to select desired organic functional materials for fabricating hybrid films to maximize their photovoltaic performance.Herein,we report the synthesis of three narrow bandgap non-fullerene conjugated polymers and further demonstrate the importance and impact of polymer crystallinity in tuning the organic-inorganic hybrid interface towards improved photovoltaic performance.In specific,we develop an organic-inorganic hybrid active layer using a newly synthesized polymer with relatively weaker crystallinity and FAPbI_(3)QDs,enabling complementary absorption and favorable interface/morphology for efficient charge separation and transport.The champion PCDOT-T/FAPbI_(3)QD hybrid device achieves a record-high efficiency of 13.11%based on the one-step coating organic/QD hybrid bulk heterojunction blend,which is significantly improved relative to the semi-crystalline polymer PYIT-based hybrid device(11.23%)and pristine QD(10.51%).We believe these findings would provide new insight into the organic/QD interface to construct desired hybrid films for high-performing optoelectronic applications.展开更多
Generally,referring to the stability of perovskite,the most studied perovskite material has been MA-free mixed-cationperovskite.The precise role of MA in the light-thermal-humid stability of perovskite solar cells sti...Generally,referring to the stability of perovskite,the most studied perovskite material has been MA-free mixed-cationperovskite.The precise role of MA in the light-thermal-humid stability of perovskite solar cells still lacks ofa systematically understanding.In this work,the evolution of crystallographic structures,intermediate phase,ultrafast dynamics,and thermal decomposition behavior of MA-mixed perovskite FA_(1-x)MA_(x)PbI_(3)(x=0–100%)areinvestigated.The influence of MA on the stability of devices under heat,light,and humidity exposure arerevealed.In the investigated compositional space(x=0–100%),device efficiencies vary from 19.5%to 22.8%,andthe light,thermal,and humidity exposure stability of the related devices are obviously improved forFA1-xMAxPbI_(3)(x=20%–30%).Incorporation 20%–30%of MA cations lowers nucleation barrier and causes asignificant volume shrinkage,which enhances the interaction between FA and I,thus improving crystallizationand stability of the FA_(1-x)MA_(x)PbI_(3).Thermal behavior analysis reveals that the decomposition temperature of FA_(0.8)MA_(0.2)PbI_(3)reaches 247℃(FAPbI_(3),233℃)and trace amounts of MA cations enhance the thermal stability ofthe perovskite.Remarkably,we observe lattice shrinkage using spherical aberration corrected transmissionelectron microscope(AC-TEM).This work implies that stabilizing perovskites will be realized by incorporatingtrace amounts of MA,which improve the crystallization and carrier transport,leading to improved stability andperformances.展开更多
Birefringence and second harmonic generation(SHG)are important optical properties of functional crystals.However,it is relatively rare for a compound to exhibit both enhanced properties simultaneously.In this study,we...Birefringence and second harmonic generation(SHG)are important optical properties of functional crystals.However,it is relatively rare for a compound to exhibit both enhanced properties simultaneously.In this study,we used DFT calculations to discover an ideal functional gene:protonated 3,5-dipicolinic acid(C_(7)H_(4)NO_(4),HDPA).By combining HPDA with the traditional IO_(3)-anion,we obtained a non-centrosymmetric and polar semiorganic iodate,namely HDPA(IO_(3)).The organic cations and iodate anions in HDPA(IO_(3))are bridged via the N-H···O and O-H···O hydrogen bonds,forming the wave-shaped layers.The synergistic effect between the expandedπ-conjugation of the organic cation and the stereochemically active lone pair electrons in the inorganic iodate anion results that HDPA(IO_(3))exhibiting a strong SHG effect,3.6 times that of KH_(2)PO_(4),and an unusually large birefringence of 0.35 at 546 nm,larger than most of SHG-active iodates.Additionally,HDPA(IO_(3))has a wide bandgap of 4.12 e V with a corresponding cutoff edge at 269 nm,indicating its potential as a promising short-wave ultraviolet(UV)optical crystal.展开更多
Searching for compatible electrolytes with Ni_(0.8)C_(00.15)Al_(0.05)LiO_(2-δ)(NCAL)electrodes that exhibit high ionic conductivity at low operational temperatures(<550℃)is crucial for advancing ceramics fuel cel...Searching for compatible electrolytes with Ni_(0.8)C_(00.15)Al_(0.05)LiO_(2-δ)(NCAL)electrodes that exhibit high ionic conductivity at low operational temperatures(<550℃)is crucial for advancing ceramics fuel cells(CFCs)research.In this work,the experimental and theoretical analyses demonstrate that the highly stable single-phase Gd_(3)Ga_(5)O_(12)(GGO)garnet structure,composed of Gd-O octahedrons and Ga-O tetrahedrons,provides more active sites for ion transport,resulting in enhanced peak power density(PPD)and stable open circuit voltage(OCV)at low operational temperatures.The unique internal garnet structure effectively reduces the interfacial impedance of the prepared fuel cell device,provides more active sites at triple-phase boundarie region,and increases the electrochemical stability.As a result,the constructed fuel cell device can deliver a superior peak power density of 770 mW/cm^(2)at 490℃.In addition,X-ray photoelectron spectroscopy,electrochemical impedance spectroscopy,and theoretical calculations further demonstrate electrolyte effectiveness of GGO,enabling stable an OCV even at a low temperature of 370℃under a H_(2)/air environment.This work contributes to a deeper understanding of the underlying mechanisms of a single-layer fuel cell device,which is essential for advancing this promising energy technology,even at a very low temperature of 370℃.展开更多
Heat dissipation highly relies on the thermal conductivity(κ)of materials.Materials with large bandgaps and signifcant atomic mass ratios,such as BAs,SiC,andθ-TaN,have attracted considerable attention due to their p...Heat dissipation highly relies on the thermal conductivity(κ)of materials.Materials with large bandgaps and signifcant atomic mass ratios,such as BAs,SiC,andθ-TaN,have attracted considerable attention due to their potential for achieving ultra-highκ,with BAs serving as a particularly representative example due to its unique combination of large bandgap and high thermal conductivity.In this paper,the efects of atomic mass modifcation on phonon bandgap andκare systematically investigated using a BAs model,accounting for both three-and four-phonon scattering processes.A 20%increase inκcan be obtained by substituting B,achieved through widening the phonon bandgap,which suppresses phonon scattering.Notably,the AAOO four-phonon scattering channel is more suppressed than the AAO three-phonon channel,leading to an increased phonon lifetime(τ).For As,κcan also be enhanced by 5%when replaced by lighter atoms,such as^(69)As,primarily due to the increased phonon group velocity(υ).We systematically clarify how atomic-mass-induced bandgap variations afectτ,υ,and thereforeκin wide-bandgap systems.Our work provides a specifc scheme for further improving the ultra-highκof materials with large bandgaps,which possesses great guiding signifcance.展开更多
In this article,we present a theoretical study on the sub-bandgap refractive indexes and optical properties of Sidopedβ-Ga_(2)O_(3) thin films based on newly developed models.The measured sub-bandgap refractive index...In this article,we present a theoretical study on the sub-bandgap refractive indexes and optical properties of Sidopedβ-Ga_(2)O_(3) thin films based on newly developed models.The measured sub-bandgap refractive indexes ofβ-Ga_(2)O_(3) thin film are explained well with the new model,leading to the determination of an explicit analytical dispersion of refractive indexes for photon energy below an effective optical bandgap energy of 4.952 eV for theβ-Ga_(2)O_(3) thin film.Then,the oscillatory structures in long wavelength regions in experimental transmission spectra of Si-dopedβ-Ga_(2)O_(3) thin films with different Si doping concentrations are quantitively interpreted utilizing the determined sub-bandgap refractive index dispersion.Meanwhile,effective optical bandgap values of Si-dopedβ-Ga_(2)O_(3) thin films are further determined and are found to decrease with increasing the Si doping concentration as expectedly.In addition,the sub-bandgap absorption coefficients of Si-dopedβ-Ga_(2)O_(3) thin film are calculated under the frame of the Franz–Keldysh mechanism due to the electric field effect of ionized Si impurities.The theoretical absorption coefficients agree with the available experimental data.These key parameters obtained in the present study may enrich the present understanding of the sub-bandgap refractive indexes and optical properties of impurity-dopedβ-Ga_(2)O_(3) thin films.展开更多
A bandgap voltage reference is presented with a piecewise linear compensating circuit in order to reduce the temperature coefficient.The basic principle is to divide the whole operating temperature range into some su...A bandgap voltage reference is presented with a piecewise linear compensating circuit in order to reduce the temperature coefficient.The basic principle is to divide the whole operating temperature range into some sub ranges.At different temperature sub ranges the bandgap reference can be compensated by different linear functions.Since the temperature sub range is much narrower than the whole range,the compensation error can be reduced significantly.Theoretically,the precision can be improved unlimitedly if the sub ranges are narrow enough.In the given example,with only three temperature sub ranges,the temperature coefficient of a conventional bandgap reference drops from 1 5×10 -5 /℃ to 2×10 -6 /℃ over the -40℃ to 120℃ temperature range.展开更多
A novel CMOS bandgap reference is presented. The output reference of this new current mode structure can be set to an arbitrary value above the bandgap voltage of silicon,avoiding offset in application. It also overco...A novel CMOS bandgap reference is presented. The output reference of this new current mode structure can be set to an arbitrary value above the bandgap voltage of silicon,avoiding offset in application. It also overcomes the systematic mismatch of conventional current mode bandgap references. The proposed bandgap reference has been implemented in UMC 0.18μm mixed mode technology. Under the supply voltage of 1.6V, the proposed bandgap reference provides an output reference of 1.45V and consumes 27μA of supply current. Using no curvature compensation,it can reach a temperature coefficient of 23ppm/℃ from 30 to 150℃ with a line regulation of 2. 1mV/V from 1.6 to 3V and a PSRR of 40dB at DC frequency. The chip area of the bandgap reference （without pad） is 0. 088mm^2.展开更多
A low voltage bandgap reference with curvature compensation is presented. Using current mode structure, the proposed bandgap circuit has a minimum voltage of 900mV. Compensated through the VEB linearization technique,...A low voltage bandgap reference with curvature compensation is presented. Using current mode structure, the proposed bandgap circuit has a minimum voltage of 900mV. Compensated through the VEB linearization technique, this bandgap reference can reach a temperature coefficient of 10ppmFC from 0 to 150℃. With a 1.1V supply voltage,the supply current is 43μA and the PSRR is 55dB at DC frequency. This bandgap reference has been verified in a UMC 0.18μm mixed mode CMOS technology and occupies 0. 186mm^2 of chip area.展开更多
The transitions of E0 ,E0 ＋A0, and E＋ in dilute GaAs（1-x） Nx alloys with x = 0.10% ,0.22% ,0.36% ,and 0.62% are observed by micro-photoluminescence. Resonant Raman scattering results further confirm that they are ...The transitions of E0 ,E0 ＋A0, and E＋ in dilute GaAs（1-x） Nx alloys with x = 0.10% ,0.22% ,0.36% ,and 0.62% are observed by micro-photoluminescence. Resonant Raman scattering results further confirm that they are from the intrinsic emissions in the studied dilute GaAsN alloys rather than some localized exciton emissions in the GaAsN alloys. The results show that the nitrogen-induced E E＋ and E0 ＋ A0 transitions in GaAsN alloys intersect at a nitrogen content of about 0.16%. It is demonstrated that a small amount of isoelectronic doping combined with micro-photoluminescence allows direct observation of above band gap transitions that are not usually accessible in photoluminescence.展开更多
This paper proposes a resistorless CMOS bandgap reference (BGR) circuit capable of generating a voltage less than 1V and presents a high performance start up circuit that can make the BGR circuit achieve the correct ...This paper proposes a resistorless CMOS bandgap reference (BGR) circuit capable of generating a voltage less than 1V and presents a high performance start up circuit that can make the BGR circuit achieve the correct operation point at power on. The simulation with Hspice was carried out using a 0 25 μm CMOS process. The results indicate that the proposed BGR circuit can operate on a 2 2 to 3 3 V power supply and its output voltage has a variation of 11 mV at -10 to 80 ℃.展开更多
A CMOS bandgap reference （BGR） without a resistor,with a high power supply rejection ratio and output be- low 1V is proposed. The circuit is suited for on-chip voltage down converters. The BGR is designed and fabric...A CMOS bandgap reference （BGR） without a resistor,with a high power supply rejection ratio and output be- low 1V is proposed. The circuit is suited for on-chip voltage down converters. The BGR is designed and fabricated using an HUTC 0.18μm CMOS process. The silicon area is only 0. 031mm^2 excluding pads and electrostatic-discharge （ESD） protec- tion circuits. Experimental results show that the PSRR of the proposed BGR at 100Hz and lkHz achieves, respectively, - 70 and 62dB using the pre-regulator. The proposed BGR circuit generates an output voltage of 0. 5582V with a varia- tion of 1.5mV in a temperature range from 0 to 85℃. The deviation of the output voltage is within 2mV when the power supply voltage VDD changes from 2.4 to 4V.展开更多
A simple model for approximate bandgap structure calculation of all-solid photonic bandgap fibre based on an array of rings is proposed. In this model calculated are only the potential modes of a unit cell, which is a...A simple model for approximate bandgap structure calculation of all-solid photonic bandgap fibre based on an array of rings is proposed. In this model calculated are only the potential modes of a unit cell, which is a high-index ring in the low-index background for this fibre, rather than the whole cladding periodic structure based on Bloch＇s theorem to find the bandgap. Its accuracy is proved by comparing its results with the results obtained by using the accurate full-vector plane-wave method. High speed in computation is its great advantage over the other exact methods, because it only needs to find the roots of one-dimensional analytical expressions. And the results of this model, mode plots, offer an ideal environment to explore the basic properties of photonie bandgap clearly.展开更多
基金supported by the National Natural Science Foundation of China(NSFC)under grant No.62204235。
文摘This paper introduces a high-precision bandgap reference(BGR)designed for battery management systems(BMS),fea-turing an ultra-low temperature coefficient(TC)and line sensitivity(LS).The BGR employs a current-mode scheme with chopped op-amps and internal clock generators to eliminate op-amp offset.A low dropout regulator(LDO)and a pre-regula-tor enhance output driving and LS,respectively.Curvature compensation enhances the TC by addressing higher-order nonlinear-ity.These approaches,effective near room temperature,employs trimming at both 20 and 60°C.When combined with fixed cur-vature correction currents,it achieves an ultra-low TC for each chip.Implemented in a CMOS 180 nm process,the BGR occu-pies 0.548 mm²and operates at 2.5 V with 84μA current draw from a 5 V supply.An average TC of 2.69 ppm/℃ with two-point trimming and 0.81 ppm/℃ with multi-point trimming are achieved over the temperature range of-40 to 125℃.It accommo-dates a load current of 1 mA and an LS of 42 ppm/V,making it suitable for precise BMS applications.
基金Supported by Bissell Distinguished Professor Endowment Fund at UNC-Charlotte。
文摘Although there are numerous optical spectroscopy techniques and methods that have been used to extract the fundamental bandgap of a semiconductor,most of them belong to one of these three approaches:(1)the excitonic absorption,(2)modulation spectroscopy,and(3)the most widely used Tauc-plot.The excitonic absorption is based on a many-particle theory,which is physically the most correct approach,but requires more stringent crystalline quality and appropriate sample preparation and experimental implementation.The Tauc-plot is based on a single-particle theo⁃ry that neglects the many-electron effects.Modulation spectroscopy analyzes the spectroscopy features in the derivative spectrum,typically,of the reflectance and transmission under an external perturbation.Empirically,the bandgap ener⁃gy derived from the three approaches follow the order of E_(ex)>E_(MS)>E_(TP),where three transition energies are from exci⁃tonic absorption,modulation spectroscopy,and Tauc-plot,respectively.In principle,defining E_(g) as the single-elec⁃tron bandgap,we expect E_(g)>E_(ex),thus,E_(g)>E_(TP).In the literature,E_(TP) is often interpreted as E_(g),which is conceptual⁃ly problematic.However,in many cases,because the excitonic peaks are not readily identifiable,the inconsistency be⁃tween E_(g) and E_(TP) becomes invisible.In this brief review,real world examples are used(1)to illustrate how excitonic absorption features depend sensitively on the sample and measurement conditions;(2)to demonstrate the differences between E_(ex),E_(MS),and E_(TP) when they can be extracted simultaneously for one sample;and(3)to show how the popular⁃ly adopted Tauc-plot could lead to misleading results.Finally,it is pointed out that if the excitonic absorption is not ob⁃servable,the modulation spectroscopy can often yield a more useful and reasonable bandgap than Tauc-plot.
基金supported by the National Natural Science Foundation of China(Nos.12364015 and 52176072)the Five-Year Action Plan for Shccig-Qinling Program and Key Project of Hubei Province Key Research and Development Plan(No.2021BCA140)+4 种基金the Industry and Education Combination Innovation Platform of Intelligent Manufacturing and Graduate Joint Training Base at Guizhou University(No.2020-520000-83-01-324061)the National Key Research and Development Plan(No.2022YFF0706500)Guizhou University Natural Science Special(special post)Research Fund(No.(2023)17)Guizhou Engineering Research Center for Smart Services(No.2203-520102-04-04-298868)the Construction of Science and Technology Platform of Guiyang(No.[2023]7-3).
文摘Low energy-storage density and inferior thermal stability are a long-term obstacle to the advancement of pulse power devices.Herein,these concerns are addressed by improving bandgap and fabricating polar nanoregions,and the superior high efficiency of~86.7%,excellent thermal stability of~2%(31-160℃)and energy density of~6.8 J·cm^(-3)are achieved in Bi_(0.5)Na_(0.5)TiO_(3)-La_(0.1)Sr_(0.8)TiO_(3)-δ-NaNbO_(3)ceramics.The high breakdown strength(460 kV·cm^(-1))is ascribed to the broadened bandgap and refined grain.Slim ferroelectric loops originate from the construction of polar nanoregions(PNRs)in a pseudocubic matrix,and transmission electron microscope and piezoelectric force microscope measurements reveal the occurrence of PNRs.The phase-field stimulation and UV-Vis spectrophotometer measurement reveal that the increased grain boundary density and bandgap are beneficial for promoting breakdown strength.The strategy provides an efficient path to prepare Bi_(0.5)Na_(0.5)TiO_(3)La_(0.1)Sr_(0.8)TiO_(3)-δ-based ceramics with superior efficiency,high energy density and outstanding thermal stability.
基金financially supported by the Natural Science Foundation of China(52372226,52202300,62288102,62350013,52303325)National Key Research and Development Program of China(2023YFB3608900)+5 种基金the Postdoctoral Fellowship Program ofthe China postdoctoral Science Foundation(CPSF)(Grant GZC20233506)the China Postdoctoral Science Foundation(Grant2024M764252)the Natural Science Foundation of Chongqing China(2023NSCQ-MSX0097)Guangdong Basic and Applied Basic Research Foundation(2024A1515010918)Shenzhen Science and Technology Program(Grant JCYJ20240813150819026)the Fundamental Research Funds for the Central Universities。
文摘Lead-tin(Pb-Sn)perovskites with an ideal bandgap of 1.34-1.40 eV show great promise in perovskite solar cells(PSCs).Recently,to address the environmental pollution and Sn^(2+)oxidation problems of dimethyl sulfoxide,methylammonium acetate(MAAc)ionic liquid has been developed as an alternative to fabricate ideal bandgap MAPb_(0.7)Sn_(0.3)I_(3)(1.36 eV)film via hot-casting in air.However,the spontaneous crystallization of Pb-Sn perovskite initiated by heat-induced supersaturation is fast and random,setting critical challenges in regulating crystal growth during the film-forming process.Herein,a lattice activation strategy is developed to control the crystallization dynamics of MAPb_(0.7)Sn_(0.3)I_(3)in MAAc to produce films with micrometer-sized grains in air.FA is shown to activate the crystal lattice that facilitates the formation of intermediates and balances the crystal growth of MAPb_(0.7)Sn_(0.3)I_(3),producing films with a grain size of 2.78±0.17μm.Furthermore,4-fluoro-phenethylammonium and phenethylammonium are adopted to passivate the defects in the film and promote the energy level alignment at the top interface,respectively.The optimized PSC device achieved an efficiency of 18.24%with a short-circuit current of 29.84 mA/cm^(2),which are both the highest values in 1.36 eV Pb-Sn PSCs to date.Notably,the unencapsulated devices show excellent storage and air stability under various conditions.
基金Project supported by the National Natural Science Foundation of China(Nos.11872233,U2341231,and 12102245)。
文摘A novel elastic metamaterial is proposed with the aim of achieving lowfrequency broad bandgaps and bandgap regulation.The band structure of the proposed metamaterial is calculated based on the Floquet-Bloch theorem,and the boundary modes of each bandgap are analyzed to understand the effects of each component of the unit cell on the bandgap formation.It is found that the metamaterials with a low elastic modulus of ligaments can generate flexural wave bandgaps below 300 Hz.Multi-frequency vibrations can be suppressed through the selective manipulation of bandgaps.The dual-graded design of metamaterials that can significantly improve the bandgap width is proposed based on parametric studies.A new way that can regulate the bandgap is revealed by studying the graded elastic modulus in the substrate.The results demonstrate that the nonlinear gradient of the elastic modulus in the substrate offers better bandgap performance.Based on these analyses,the proposed elastic metamaterials can pave the way for multi-frequency vibration control,low-frequency bandgap broadening,and bandgap tuning.
基金supported by the National Research Foundation of Korea(NRF)funded by the Korean government(MSIT)(Grant number:RS-2025-02316700,and RS-2025-00522430)the China Scholarship Council Program。
文摘The bandgap is a key parameter for understanding and designing hybrid perovskite material properties,as well as developing photovoltaic devices.Traditional bandgap calculation methods like ultravioletvisible spectroscopy and first-principles calculations are time-and power-consuming,not to mention capturing bandgap change mechanisms for hybrid perovskite materials across a wide range of unknown space.In the present work,an artificial intelligence ensemble comprising two classifiers(with F1 scores of 0.9125 and 0.925)and a regressor(with mean squared error of 0.0014 eV)is constructed to achieve high-precision prediction of the bandgap.The bandgap perovskite dataset is established through highthroughput prediction of bandgaps by the ensemble.Based on the self-built dataset,partial dependence analysis(PDA)is developed to interpret the bandgap influential mechanism.Meanwhile,an interpretable mathematical model with an R^(2)of 0.8417 is generated using the genetic programming symbolic regression(GPSR)technique.The constructed PDA maps agree well with the Shapley Additive exPlanations,the GPSR model,and experiment verification.Through PDA,we reveal the boundary effect,the bowing effect,and their evolution trends with key descriptors.
基金financially supported by the National Key Research and Development Program of China(2022YFE0110300)the National Natural Science Foundation of China(52261145696 and 52473187)+1 种基金the“111”Projectthe Collaborative Innovation Center of Suzhou Nano Science and Technology,Soochow University。
文摘Organic-inorganic hybrid solar cells consisting of organic conjugated materials and inorganic quantum dots(QDs)have been of great interest during the past two decades.However,it is still challenging to select desired organic functional materials for fabricating hybrid films to maximize their photovoltaic performance.Herein,we report the synthesis of three narrow bandgap non-fullerene conjugated polymers and further demonstrate the importance and impact of polymer crystallinity in tuning the organic-inorganic hybrid interface towards improved photovoltaic performance.In specific,we develop an organic-inorganic hybrid active layer using a newly synthesized polymer with relatively weaker crystallinity and FAPbI_(3)QDs,enabling complementary absorption and favorable interface/morphology for efficient charge separation and transport.The champion PCDOT-T/FAPbI_(3)QD hybrid device achieves a record-high efficiency of 13.11%based on the one-step coating organic/QD hybrid bulk heterojunction blend,which is significantly improved relative to the semi-crystalline polymer PYIT-based hybrid device(11.23%)and pristine QD(10.51%).We believe these findings would provide new insight into the organic/QD interface to construct desired hybrid films for high-performing optoelectronic applications.
基金supported by the Nation Key R&D Program of China(Grant Numbers:2023YFC3906103)the Natural Science Foundation of Hunan Province(No.2022JJ30757)+1 种基金Entrepreneurship Research Team Project(No.1053320220430)Guangdong Science and Technology Planning Project(2018B030323010).
文摘Generally,referring to the stability of perovskite,the most studied perovskite material has been MA-free mixed-cationperovskite.The precise role of MA in the light-thermal-humid stability of perovskite solar cells still lacks ofa systematically understanding.In this work,the evolution of crystallographic structures,intermediate phase,ultrafast dynamics,and thermal decomposition behavior of MA-mixed perovskite FA_(1-x)MA_(x)PbI_(3)(x=0–100%)areinvestigated.The influence of MA on the stability of devices under heat,light,and humidity exposure arerevealed.In the investigated compositional space(x=0–100%),device efficiencies vary from 19.5%to 22.8%,andthe light,thermal,and humidity exposure stability of the related devices are obviously improved forFA1-xMAxPbI_(3)(x=20%–30%).Incorporation 20%–30%of MA cations lowers nucleation barrier and causes asignificant volume shrinkage,which enhances the interaction between FA and I,thus improving crystallizationand stability of the FA_(1-x)MA_(x)PbI_(3).Thermal behavior analysis reveals that the decomposition temperature of FA_(0.8)MA_(0.2)PbI_(3)reaches 247℃(FAPbI_(3),233℃)and trace amounts of MA cations enhance the thermal stability ofthe perovskite.Remarkably,we observe lattice shrinkage using spherical aberration corrected transmissionelectron microscope(AC-TEM).This work implies that stabilizing perovskites will be realized by incorporatingtrace amounts of MA,which improve the crystallization and carrier transport,leading to improved stability andperformances.
基金supported by the National Natural Science Foundation of China(Nos.22205037 and 22373014)the Natural Science Foundation of Fujian Province(No.2023J01498)。
文摘Birefringence and second harmonic generation(SHG)are important optical properties of functional crystals.However,it is relatively rare for a compound to exhibit both enhanced properties simultaneously.In this study,we used DFT calculations to discover an ideal functional gene:protonated 3,5-dipicolinic acid(C_(7)H_(4)NO_(4),HDPA).By combining HPDA with the traditional IO_(3)-anion,we obtained a non-centrosymmetric and polar semiorganic iodate,namely HDPA(IO_(3)).The organic cations and iodate anions in HDPA(IO_(3))are bridged via the N-H···O and O-H···O hydrogen bonds,forming the wave-shaped layers.The synergistic effect between the expandedπ-conjugation of the organic cation and the stereochemically active lone pair electrons in the inorganic iodate anion results that HDPA(IO_(3))exhibiting a strong SHG effect,3.6 times that of KH_(2)PO_(4),and an unusually large birefringence of 0.35 at 546 nm,larger than most of SHG-active iodates.Additionally,HDPA(IO_(3))has a wide bandgap of 4.12 e V with a corresponding cutoff edge at 269 nm,indicating its potential as a promising short-wave ultraviolet(UV)optical crystal.
基金supported by the Jiangsu Fundamental Research Program(JSSCRC2021491)Ongoing Research Funding Program(ORF-2025-391)。
文摘Searching for compatible electrolytes with Ni_(0.8)C_(00.15)Al_(0.05)LiO_(2-δ)(NCAL)electrodes that exhibit high ionic conductivity at low operational temperatures(<550℃)is crucial for advancing ceramics fuel cells(CFCs)research.In this work,the experimental and theoretical analyses demonstrate that the highly stable single-phase Gd_(3)Ga_(5)O_(12)(GGO)garnet structure,composed of Gd-O octahedrons and Ga-O tetrahedrons,provides more active sites for ion transport,resulting in enhanced peak power density(PPD)and stable open circuit voltage(OCV)at low operational temperatures.The unique internal garnet structure effectively reduces the interfacial impedance of the prepared fuel cell device,provides more active sites at triple-phase boundarie region,and increases the electrochemical stability.As a result,the constructed fuel cell device can deliver a superior peak power density of 770 mW/cm^(2)at 490℃.In addition,X-ray photoelectron spectroscopy,electrochemical impedance spectroscopy,and theoretical calculations further demonstrate electrolyte effectiveness of GGO,enabling stable an OCV even at a low temperature of 370℃under a H_(2)/air environment.This work contributes to a deeper understanding of the underlying mechanisms of a single-layer fuel cell device,which is essential for advancing this promising energy technology,even at a very low temperature of 370℃.
基金supported by the National Key Research and Development Program of China(Grant No.2023YFA1407001)the Department of Science and Technology of Jiangsu Province(Grant No.BK20220032)+1 种基金support from the Guang Dong Basic and Applied Basic Research Foundation(Grant No.2023A1515010365)support from the Postgraduate Research and Practice Innovation Program of Jiangsu Province under Grant No.KYCX25_1934。
文摘Heat dissipation highly relies on the thermal conductivity(κ)of materials.Materials with large bandgaps and signifcant atomic mass ratios,such as BAs,SiC,andθ-TaN,have attracted considerable attention due to their potential for achieving ultra-highκ,with BAs serving as a particularly representative example due to its unique combination of large bandgap and high thermal conductivity.In this paper,the efects of atomic mass modifcation on phonon bandgap andκare systematically investigated using a BAs model,accounting for both three-and four-phonon scattering processes.A 20%increase inκcan be obtained by substituting B,achieved through widening the phonon bandgap,which suppresses phonon scattering.Notably,the AAOO four-phonon scattering channel is more suppressed than the AAO three-phonon channel,leading to an increased phonon lifetime(τ).For As,κcan also be enhanced by 5%when replaced by lighter atoms,such as^(69)As,primarily due to the increased phonon group velocity(υ).We systematically clarify how atomic-mass-induced bandgap variations afectτ,υ,and thereforeκin wide-bandgap systems.Our work provides a specifc scheme for further improving the ultra-highκof materials with large bandgaps,which possesses great guiding signifcance.
基金This study was financially supported by the National Natural Science Foundation of China(No.12074324)the Shenzhen Municipal Science and Technology Innovation Council(No.JCJY20180508163404043).
文摘In this article,we present a theoretical study on the sub-bandgap refractive indexes and optical properties of Sidopedβ-Ga_(2)O_(3) thin films based on newly developed models.The measured sub-bandgap refractive indexes ofβ-Ga_(2)O_(3) thin film are explained well with the new model,leading to the determination of an explicit analytical dispersion of refractive indexes for photon energy below an effective optical bandgap energy of 4.952 eV for theβ-Ga_(2)O_(3) thin film.Then,the oscillatory structures in long wavelength regions in experimental transmission spectra of Si-dopedβ-Ga_(2)O_(3) thin films with different Si doping concentrations are quantitively interpreted utilizing the determined sub-bandgap refractive index dispersion.Meanwhile,effective optical bandgap values of Si-dopedβ-Ga_(2)O_(3) thin films are further determined and are found to decrease with increasing the Si doping concentration as expectedly.In addition,the sub-bandgap absorption coefficients of Si-dopedβ-Ga_(2)O_(3) thin film are calculated under the frame of the Franz–Keldysh mechanism due to the electric field effect of ionized Si impurities.The theoretical absorption coefficients agree with the available experimental data.These key parameters obtained in the present study may enrich the present understanding of the sub-bandgap refractive indexes and optical properties of impurity-dopedβ-Ga_(2)O_(3) thin films.
文摘A bandgap voltage reference is presented with a piecewise linear compensating circuit in order to reduce the temperature coefficient.The basic principle is to divide the whole operating temperature range into some sub ranges.At different temperature sub ranges the bandgap reference can be compensated by different linear functions.Since the temperature sub range is much narrower than the whole range,the compensation error can be reduced significantly.Theoretically,the precision can be improved unlimitedly if the sub ranges are narrow enough.In the given example,with only three temperature sub ranges,the temperature coefficient of a conventional bandgap reference drops from 1 5×10 -5 /℃ to 2×10 -6 /℃ over the -40℃ to 120℃ temperature range.
文摘A novel CMOS bandgap reference is presented. The output reference of this new current mode structure can be set to an arbitrary value above the bandgap voltage of silicon,avoiding offset in application. It also overcomes the systematic mismatch of conventional current mode bandgap references. The proposed bandgap reference has been implemented in UMC 0.18μm mixed mode technology. Under the supply voltage of 1.6V, the proposed bandgap reference provides an output reference of 1.45V and consumes 27μA of supply current. Using no curvature compensation,it can reach a temperature coefficient of 23ppm/℃ from 30 to 150℃ with a line regulation of 2. 1mV/V from 1.6 to 3V and a PSRR of 40dB at DC frequency. The chip area of the bandgap reference （without pad） is 0. 088mm^2.
文摘A low voltage bandgap reference with curvature compensation is presented. Using current mode structure, the proposed bandgap circuit has a minimum voltage of 900mV. Compensated through the VEB linearization technique, this bandgap reference can reach a temperature coefficient of 10ppmFC from 0 to 150℃. With a 1.1V supply voltage,the supply current is 43μA and the PSRR is 55dB at DC frequency. This bandgap reference has been verified in a UMC 0.18μm mixed mode CMOS technology and occupies 0. 186mm^2 of chip area.
文摘The transitions of E0 ,E0 ＋A0, and E＋ in dilute GaAs（1-x） Nx alloys with x = 0.10% ,0.22% ,0.36% ,and 0.62% are observed by micro-photoluminescence. Resonant Raman scattering results further confirm that they are from the intrinsic emissions in the studied dilute GaAsN alloys rather than some localized exciton emissions in the GaAsN alloys. The results show that the nitrogen-induced E E＋ and E0 ＋ A0 transitions in GaAsN alloys intersect at a nitrogen content of about 0.16%. It is demonstrated that a small amount of isoelectronic doping combined with micro-photoluminescence allows direct observation of above band gap transitions that are not usually accessible in photoluminescence.
文摘This paper proposes a resistorless CMOS bandgap reference (BGR) circuit capable of generating a voltage less than 1V and presents a high performance start up circuit that can make the BGR circuit achieve the correct operation point at power on. The simulation with Hspice was carried out using a 0 25 μm CMOS process. The results indicate that the proposed BGR circuit can operate on a 2 2 to 3 3 V power supply and its output voltage has a variation of 11 mV at -10 to 80 ℃.
文摘A CMOS bandgap reference （BGR） without a resistor,with a high power supply rejection ratio and output be- low 1V is proposed. The circuit is suited for on-chip voltage down converters. The BGR is designed and fabricated using an HUTC 0.18μm CMOS process. The silicon area is only 0. 031mm^2 excluding pads and electrostatic-discharge （ESD） protec- tion circuits. Experimental results show that the PSRR of the proposed BGR at 100Hz and lkHz achieves, respectively, - 70 and 62dB using the pre-regulator. The proposed BGR circuit generates an output voltage of 0. 5582V with a varia- tion of 1.5mV in a temperature range from 0 to 85℃. The deviation of the output voltage is within 2mV when the power supply voltage VDD changes from 2.4 to 4V.
基金Project supported by the National High Technology Research and Development Program of China (Grant No 2004AA31G200)Beijing Jiaotong University Foundation, China (Grant No 2005SM002)
文摘A simple model for approximate bandgap structure calculation of all-solid photonic bandgap fibre based on an array of rings is proposed. In this model calculated are only the potential modes of a unit cell, which is a high-index ring in the low-index background for this fibre, rather than the whole cladding periodic structure based on Bloch＇s theorem to find the bandgap. Its accuracy is proved by comparing its results with the results obtained by using the accurate full-vector plane-wave method. High speed in computation is its great advantage over the other exact methods, because it only needs to find the roots of one-dimensional analytical expressions. And the results of this model, mode plots, offer an ideal environment to explore the basic properties of photonie bandgap clearly.
