Growth,leaf anatomy,and photosynthesis of cotton(Gossypium hirsutum L.)seedlings in response to four light-emitting diodes and high pressure sodium lamp

Background Light is a critical factor in plant growth and development,particularly in controlled environments.Light-emitting diodes(LEDs)have become a reliable alternative to conventional high pressure sodium(HSP)lamps because they are more efficient and versatile in light sources.In contrast to well-known specialized LED light spectra for vegetables,the appropriate LED lights for crops such as cotton remain unknown.Results In this growth chamber study,we selected and compared four LED lights with varying percentages(26.44%–68.68%)of red light(R,600–700 nm),combined with other lights,for their effects on growth,leaf anatomy,and photosynthesis of cotton seedlings,using HSP lamp as a control.The total photosynthetic photon flux density(PPFD)was(215±2)μmol·m-2·s-1 for all LEDs and HSP lamp.The results showed significant differences in all tested parameters among lights,and the percentage of far red(FR,701–780 nm)within the range of 3.03%–11.86%was positively correlated with plant growth(characterized by leaf number and area,plant height,stem diameter,and total biomass),palisade layer thickness,photosynthesis rate(Pn),and stomatal conductance(Gs).The ratio of R/FR(4.445–11.497)negatively influenced the growth of cotton seedlings,and blue light(B)suppressed stem elongation but increased palisade cell length,chlorophyll content,and Pn.Conclusion The LED 2 was superior to other LED lights and HSP lamp.It had the highest ratio of FR within the total PPFD(11.86%)and the lowest ratio of R/FR(4.445).LED 2 may therefore be used to replace HPS lamp under controlled environments for the study of cotton at the seedling stage.

Sweat-permeable electronic patches by designing threedimensional liquid diodes

Wearable electronics face a significant challenge related to the limited permeability of electronic materials/devices.This issue results in sweat accumulation across the interface of the device and skin following a specific period of use[1−3].Not only does it bring about discomfort for users regarding thermos-physiology,but it also has a detrimental effect on interface adhesion and signal quality,thus hindering exact sig-nal monitoring during prolonged periods[4−6].

GaN based ultraviolet laser diodes

In the past few years,many groups have focused on the research and development of GaN-based ultraviolet laser diodes(UV LDs).Great progresses have been achieved even though many challenges exist.In this article,we analyze the challenges of developing GaN-based ultraviolet laser diodes,and the approaches to improve the performance of ultraviolet laser diode are reviewed.With these techniques,room temperature(RT)pulsed oscillation of AlGaN UVA(ultraviolet A)LD has been realized,with a lasing wavelength of 357.9 nm.Combining with the suppression of thermal effect,the high output power of 3.8 W UV LD with a lasing wavelength of 386.5 nm was also fabricated.

Recent Advances in Patterning Strategies for Full‑Color Perovskite Light‑Emitting Diodes

Metal halide perovskites have emerged as promising light-emitting materials for next-generation displays owing to their remarkable material characteristics including broad color tunability,pure color emission with remarkably narrow bandwidths,high quantum yield,and solution processability.Despite recent advances have pushed the luminance efficiency of monochromic perovskite light-emitting diodes(PeLEDs)to their theoretical limits,their current fabrication using the spincoating process poses limitations for fabrication of full-color displays.To integrate PeLEDs into full-color display panels,it is crucial to pattern red–green–blue(RGB)perovskite pixels,while mitigating issues such as cross-contamination and reductions in luminous efficiency.Herein,we present state-of-the-art patterning technologies for the development of full-color PeLEDs.First,we highlight recent advances in the development of efficient PeLEDs.Second,we discuss various patterning techniques of MPHs(i.e.,photolithography,inkjet printing,electron beam lithography and laserassisted lithography,electrohydrodynamic jet printing,thermal evaporation,and transfer printing)for fabrication of RGB pixelated displays.These patterning techniques can be classified into two distinct approaches:in situ crystallization patterning using perovskite precursors and patterning of colloidal perovskite nanocrystals.This review highlights advancements and limitations in patterning techniques for PeLEDs,paving the way for integrating PeLEDs into full-color panels.

Effect of annealing on the electrical performance of N-polarity GaN Schottky barrier diodes

A nitrogen-polarity(N-polarity)GaN-based high electron mobility transistor(HEMT)shows great potential for high-fre-quency solid-state power amplifier applications because its two-dimensional electron gas(2DEG)density and mobility are mini-mally affected by device scaling.However,the Schottky barrier height(SBH)of N-polarity GaN is low.This leads to a large gate leakage in N-polarity GaN-based HEMTs.In this work,we investigate the effect of annealing on the electrical characteristics of N-polarity GaN-based Schottky barrier diodes(SBDs)with Ni/Au electrodes.Our results show that the annealing time and tem-perature have a large influence on the electrical properties of N-polarity GaN SBDs.Compared to the N-polarity SBD without annealing,the SBH and rectification ratio at±5 V of the SBD are increased from 0.51 eV and 30 to 0.77 eV and 7700,respec-tively,and the ideal factor of the SBD is decreased from 1.66 to 1.54 after an optimized annealing process.Our analysis results suggest that the improvement of the electrical properties of SBDs after annealing is mainly due to the reduction of the inter-face state density between Schottky contact metals and N-polarity GaN and the increase of barrier height for the electron emis-sion from the trap state at low reverse bias.

Flexible perovskite light-emitting diodes for display applications and beyond

The flexible perovskite light-emitting diodes(FPeLEDs),which can be expediently integrated to portable and wearable devices,have shown great potential in various applications.The FPeLEDs inherit the unique optical properties of metal halide perovskites,such as tunable bandgap,narrow emission linewidth,high photoluminescence quantum yield,and particularly,the soft nature of lattice.At present,substantial efforts have been made for FPeLEDs with encouraging external quantum efficiency(EQE)of 24.5%.Herein,we summarize the recent progress in FPeLEDs,focusing on the strategy developed for perovskite emission layers and flexible electrodes to facilitate the optoelectrical and mechanical performance.In addition,we present relevant applications of FPeLEDs in displays and beyond.Finally,perspective toward the future development and applications of flexible PeLEDs are also discussed.

Enhancing the Performance of Perovskite Light-Emitting Diodes via Synergistic Effect of Defect Passivation and Dielectric Screening

Metal halide perovskites,particularly the quasi-two-dimensional perovskite subclass,have exhibited considerable potential for next-generation electroluminescent materials for lighting and display.Nevertheless,the presence of defects within these perovskites has a substantial influence on the emission efficiency and durability of the devices.In this study,we revealed a synergistic passivation mechanism on perovskite films by using a dual-functional compound of potassium bromide.The dual functional potassium bromide on the one hand can passivate the defects of halide vacancies with bromine anions and,on the other hand,can screen the charged defects at the grain boundaries with potassium cations.This approach effectively reduces the probability of carriers quenching resulting from charged defects capture and consequently enhances the radiative recombination efficiency of perovskite thin films,leading to a significant enhancement of photoluminescence quantum yield to near-unity values(95%).Meanwhile,the potassium bromide treatment promoted the growth of homogeneous and smooth film,facilitating the charge carrier injection in the devices.Consequently,the perovskite light-emitting diodes based on this strategy achieve a maximum external quantum efficiency of~21%and maximum luminance of~60,000 cd m^(-2).This work provides a deeper insight into the passivation mechanism of ionic compound additives in perovskite with the solution method.

The rise of supercapacitor diodes:Current progresses and future challenges

Supercapacitor has been widely known as a representative electrochemical energy storage device with high power density and long lifespan.Recently,with the deeper understanding of its charge storage mechanism,unidirectional-charging supercapacitor,also called supercapacitor diode(CAPode),is successfully developed based on the ion-sieving effect of its working electrode towards electrolyte ions.Because CAPode integrates mobile ion and mobile electron in one hybrid circuit,it has a great potential in the emerging fields of ion/electron coupling logic operations,human–machine interface,neural network interaction,and in vivo diagnosis and treatment.Accordingly,we herein elucidate the working mechanism and design philosophy of CAPode,and summarize the electrode materials that are suitable for constructing CAPode.Meanwhile,some other supercapacitor-based devices beyond CAPode are also introduced,and their potential applications are instructively presented.Finally,we outline the challenges and chances of CAPode-related techniques.

Proton‑Prompted Ligand Exchange to Achieve High‑Efficiency CsPbI_(3) Quantum Dot Light‑Emitting Diodes

CsPbI_(3)perovskite quantum dots(QDs)are ideal materials for the next generation of red light-emitting diodes.However,the low phase stability of CsPbI_(3)QDs and long-chain insulating capping ligands hinder the improvement of device performance.Traditional in-situ ligand replacement and ligand exchange after synthesis were often difficult to control.Here,we proposed a new ligand exchange strategy using a proton-prompted insitu exchange of short 5-aminopentanoic acid ligands with long-chain oleic acid and oleylamine ligands to obtain stable small-size CsPbI_(3)QDs.This exchange strategy maintained the size and morphology of CsPbI_(3)QDs and improved the optical properties and the conductivity of CsPbI_(3)QDs films.As a result,high-efficiency red QD-based light-emitting diodes with an emission wavelength of 645 nm demonstrated a record maximum external quantum efficiency of 24.45%and an operational half-life of 10.79 h.

Physico−mathematical model of the voltage−current characteristics of light-emitting diodes with quantum wells based on the Sah−Noyce−Shockley recombination mechanism

Herein,a physical and mathematical model of the voltage−current characteristics of a p−n heterostructure with quantum wells(QWs)is prepared using the Sah−Noyce−Shockley(SNS)recombination mechanism to show the SNS recombination rate of the correction function of the distribution of QWs in the space charge region of diode configuration.A comparison of the model voltage−current characteristics(VCCs)with the experimental ones reveals their adequacy.The technological parameters of the structure of the VCC model are determined experimentally using a nondestructive capacitive approach for determining the impurity distribution profile in the active region of the diode structure with a profile depth resolution of up to 10Å.The correction function in the expression of the recombination rate shows the possibility of determining the derivative of the VCCs of structures with QWs with a nonideality factor of up to 4.

Improving the films quality of Sn-based perovskites through additive treatment for high-performance light-emitting diodes

Hybrid lead halide perovskites have received great attention in the field of light-emitting diodes(LEDs)owing to their excellent optoelectronic properties,low cost,and high color purity.To data,the external quantum efficiency(EQE)of lead halide perovskites LEDs has been reported to exceed 20%[1].Even so,the toxicity of conventional lead has cast a gloomy shadow over their further application.

Interface engineering yields efficient perovskite light-emitting diodes

Metal-halide perovskites(MHPs)have emerged as a new class of semiconductors used in perovskite solar cells(PSCs)[1-5],perovskite light-emitting diodes(PeLEDs)[6-12],photo/X-ray detectors[13-16],and memristors[17,18].Pe LEDs can emit different light with high purity[19,20].

Materials and device engineering to achieve high-performance quantum dots light emitting diodes for display applications

Quantum dots(QDs)have attracted wide attention from academia and industry because of their advantages such as high emitting efficiency,narrow half-peak width,and continuously adjustable emitting wavelength.QDs light emitting diodes(QLEDs)are expected to become the next generation commercial display technology.This paper reviews the progress of QLED from physical mechanism,materials,to device engineering.The strategies to improve QLED performance from the perspectives of quantum dot materials and device structures are summarized.

Enhancing performance of inverted quantum-dot light-emitting diodes based on a solution-processed hole transport layer via ligand treatment

The performance of inverted quantum-dot light-emitting diodes(QLEDs)based on solution-processed hole transport layers(HTLs)has been limited by the solvent-induced damage to the quantum dot(QD)layer during the spin-coating of the HTL.The lack of compatibility between the HTL’s solvent and the QD layer results in an uneven surface,which negatively impacts the overall device performance.In this work,we develop a novel method to solve this problem by modifying the QD film with 1,8-diaminooctane to improve the resistance of the QD layer for the HTL’s solvent.The uniform QD layer leads the inverted red QLED device to achieve a low turn-on voltage of 1.8 V,a high maximum luminance of 105500 cd/m2,and a remarkable maximum external quantum efficiency of 13.34%.This approach releases the considerable potential of HTL materials selection and offers a promising avenue for the development of high-performance inverted QLEDs.

Realization of high-efficiency AlGaN deep ultraviolet light-emitting diodes with polarization-induced doping of the p-AlGaN hole injection layer

We investigate the polarization-induced doping in the gradient variation of Al composition in the pAl_(0.75)Ga_(0.25)N/Al_xGa_(1-x)N hole injection layer(HIL)for deep ultraviolet light-emitting diodes(DUV-LEDs)with an ultrathin p-GaN(4 nm)ohmic contact layer capable of emitting 277 nm.The experimental results show that the external quantum efficiency(EQE)and wall plug efficiency(WPE)of the structure graded from 0.75 to 0.55 in the HIL reach 5.49%and 5.04%,which are improved significantly by 182%and 209%,respectively,compared with the structure graded from 0.75 to 0.45,exhibiting a tremendous improvement.Both theoretical speculations and simulation results support that the larger the difference between 0.75 and x in the HIL,the higher the hole concentration that should be induced;thus,the DUV-LED has a higher internal quantum efficiency(IQE).Meanwhile,as the value of x decreases,the absorption of the DUV light emitted from the active region by the HIL is enhanced,reducing the light extraction efficiency(LEE).The IQE and LEE together affect the EQE performance of DUV-LEDs.To trade off the contradiction between the enhanced IQE and decreased LEE caused by the decrease in Al composition,the Al composition in the HIL was optimized through theoretical calculations and experiments.

Impedance spectroscopy for quantum dot light-emitting diodes

Impedance spectroscopy has been increasingly employed in quantum dot light-emitting diodes(QLEDs)to investigate the charge dynamics and device physics.In this review,we introduce the mathematical basics of impedance spectroscopy that applied to QLEDs.In particular,we focus on the Nyquist plot,Mott-Schottky analysis,capacitance-frequency and capacitance-voltage characteristics,and the d C/d V measurement of the QLEDs.These impedance measurements can provide critical information on electrical parameters such as equivalent circuit models,characteristic time constants,charge injection and recombination points,and trap distribution of the QLEDs.However,this paper will also discuss the disadvantages and limitations of these measurements.Fundamentally,this review provides a deeper understanding of the device physics of QLEDs through the application of impedance spectroscopy,offering valuable insights into the analysis of performance loss and degradation mechanisms of QLEDs.

Notch-δ-doped InP Gunn diodes for low-THz band applications

The viability of the indium phosphide(InP)Gunn diode as a source for low-THz band applications is analyzed based on a notch-δ-doped structure using the Monte Carlo modeling.The presence of theδ-doped layer could enhance the current harmonic amplitude(A0)and the fundamental operating frequency(f0)of the InP Gunn diode beyond 300 GHz as compared with the conventional notch-doped structure for a 600-nm length device.With its superior electron transport properties,the notch-δ-doped InP Gunn diodes outperform the corresponding gallium arsenide(GaAs)diodes with up to 1.35 times higher in f0 and 2.4 times larger in A0 under DC biases.An optimized InP notch-δ-doped structure is estimated to be capable of generating 0.32-W radio-frequency(RF)power at 361 GHz.The Monte Carlo simulations predict a reduction of 44%in RF power,when the device temperature is increased from 300 K to 500 K;however,its operating frequency lies at 280 GHz which is within the low-THz band.This shows that the notch-δ-doped InP Gunn diode is a highly promising signal source for low-THz sensors,which are in a high demand in the autonomous vehicle industry.

MoS_(2)/Si tunnel diodes based on comprehensive transfer technique

Due to the pristine interface of the 2D/3D face-tunneling heterostructure with an ultra-sharp doping profile, the 2D/3D tunneling field-effect transistor(TFET) is considered as one of the most promising low-power devices that can simultaneously obtain low off-state current(IOFF), high on-state current(ION) and steep subthreshold swing(SS). As a key element for the 2D/3D TFET, the intensive exploration of the tunnel diode based on the 2D/3D heterostructure is in urgent need.The transfer technique composed of the exfoliation and the release process is currently the most common approach to fabricating the 2D/3D heterostructures. However, the well-established transfer technique of the 2D materials is still unavailable.Only a small part of the irregular films can usually be obtained by mechanical exfoliation, while the choice of the chemical exfoliation may lead to the contamination of the 2D material films by the ions in the chemical etchants. Moreover, the deformation of the 2D material in the transfer process due to its soft nature also leads to the nonuniformity of the transferred film,which is one of the main reasons for the presence of the wrinkles and the stacks in the transferred film. Thus, the large-scale fabrication of the high-quality 2D/3D tunnel diodes is limited. In this article, a comprehensive transfer technique that can mend up the shortages mentioned above with the aid of the water and the thermal release tape(TRT) is proposed. Based on the method we proposed, the MoS_(2)/Si tunnel diode is experimentally demonstrated and the transferred monolayer MoS_(2) film with the relatively high crystal quality is confirmed by atomic force microscopy(AFM), scanning electron microscopy(SEM), and Raman characterizations. Besides, the prominent negative differential resistance(NDR) effect is observed at room temperature, which verifies the relatively high quality of the MoS_(2)/Si heterojunction. The bilayer MoS_(2)/Si tunnel diode is also experimentally fabricated by repeating the transfer process we proposed, followed by the specific analysis of the electrical characteristics. This study shows the advantages of the transfer technique we proposed and indicates the great application foreground of the fabricated 2D/3D heterostructure for ultralow-power tunneling devices.

Novel layout design of 4H-SiC merged PiN Schottky diodes leading to improved surge robustness

A method to improve the surge current capability of silicon carbide(SiC)merged PiN Schottky(MPS)diodes is presented and investigated via three-dimensional electro-thermal simulations.When compared with a conventional MPS diode,the proposed structure has a more uniform current distribution during bipolar conduction due to the help of the continuous P+surface,which can avoid the formation of local hotspots during the surge process.The Silvaco simulation results show that the proposed structure has a 20.29%higher surge capability and a 15.06%higher surge energy compared with a conventional MPS diode.The bipolar on-state voltage of the proposed structure is 4.69 V,which is 56.29%lower than that of a conventional MPS diode,enabling the device to enter the bipolar mode earlier during the surge process.Furthermore,the proposed structure can suppress the occurrence of‘snapback'phenomena when switching from the unipolar to the bipolar operation mode.In addition,an analysis of the surge process of MPS diodes is carried out in detail.

A landscape of β-Ga_(2)O_(3) Schottky power diodes

β-Ga_(2)O_(3) Schottky barrier diodes have undergone rapid progress in research and development for power electronic applications.This paper reviews state-of-the-art β-Ga_(2)O_(3) rectifier technologies,including advanced diode architectures that have enabled lower reverse leakage current via the reduced-surface-field effect.Characteristic device properties including onresistance,breakdown voltage,rectification ratio,dynamic switching,and nonideal effects are summarized for the different devices.Notable results on the high-temperature resilience of β-Ga_(2)O_(3) Schottky diodes,together with the enabling thermal packaging solutions,are also presented.