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.

Bifunctional flexible electrochromic energy storage devices based on silver nanowire flexible transparent electrodes

Flexible electrochromic energy storage devices(FECESDs)for powering flexible electronics have attracted considerable attention.Silver nanowires(AgNWs)are one kind of the most promising flexible transparent electrodes(FTEs)materials for the emerging flexible devices.Currently,fabricating FECESD based on AgNWs FTEs is still hindered by their intrinsic poor electrochemical stability.To address this issue,a hybrid AgNWs/Co(OH)_(2)/PEDOT:PSS electrode is proposed.The PEDOT:PSS could not only improve the resistance against electrochemical corrosion of AgNWs,but also work as functional layer to realize the color-changing and energy storage properties.Moreover,the Co(OH)_(2)interlayer further improved the color-changing and energy storage performance.Based on the improvement,we assembled the symmetrical FECESDs.Under the same condition,the areal capacitance(0.8 mF cm^(−2))and coloration efficiency(269.80 cm^(2)C−1)of AgNWs/Co(OH)_(2)/PEDOT:PSS FECESDs were obviously higher than AgNWs/PEDOT:PSS FECESDs.Furthermore,the obtained FECESDs exhibited excellent stability against the mechanical deformation.The areal capacitance remained stable during 1000 times cyclic bending with a 25 mm curvature radius.These results demonstrated the broad application potential of the AgNWs/Co(OH)_(2)/PEDOT:PSS FECESD for the emerging portable and multifunctional electronics.

Crystallization Regulation and Morphological Evolution for HTM-free Tin-Lead (1.28eV) Alloyed Perovskite Solar Cells

There have been huge achievements of all-perovskite tandem solar cells,which recently realized the highest power conversion efficiency of 24.8%.However,the complex device structure and complicated manufacture processes severely restrict the further development of all-perovskite tandem solar cells.In this work,we successfully fabricated high-efficiency hole transport material-free(HTM-free)Sn−Pb alloyed narrow bandgap perovskite solar cells(PSCs)by introducing guanidinium thiocyanate(GASCN)and hydroiodic acid(HI)into the perovskite precursor solution.GASCN and HI play a positive synergy effect during perovskite crystallization process resulting in larger grain size,fewer surface defects,and lower trap density to suppress the Sn^(2+)oxidation degradation.Furthermore,they could effectively adjust the energy level of perovskite materials,reduce the energy level difference between perovskite and ITO resulting in more efficiently transport of free hole charge carriers.As a result,with adding GASCN and HI,the achieved highest power conversion efficiency of HTM-free devices increased from 12.58%to 17.85%,which is one of the highest PCEs among all values reported to date for the HTM-free narrow-bandgap(1.2-1.4 eV)Sn−Pb binary PSCs.Moreover,the optimized device shows improved environmental stability.Our additive strategy manifests a remarkable step towards the facile,cost-efficient fabrication of HTM-free perovskite-based tandem solar cells with both high efficiency and simple fabrication process.

Facile Preparation of Fe-N-C Oxygen Reduction Electrocatalysts from Metal Organic Frameworks for Zn-Air Battery

It is critical to study efficient,stable oxygen reduction reaction(ORR)electrocatalysts due to insufficient stability and expensive price of Pt/C catalysts for Zn-air batteries.Fe–N–C electrocatalysts was synthesized by a facile solvent-green method and the efficiency of Fe–N–C optimized was studied as potential ORR electrocatalysts under alkaline condition.Results indicated that it had excellent ORR activity with E_(1/2)of 0.93 V,which was competitive to that of Pt/C-JM under the same conditions.Moreover,the assembled Zn-air battery exhibited discharge potential and charge potential of 1.2 V,2.32 V at 5 mA cm^(−2)with high stability,respectively.Overall,all results illustrated that Fe–N–C is an excellent ORR electrocatalyst in the field of metal air battery.Additionally,this work opens a good way to synthesize highly efficient electrocatalysts from metal organic framework and to investigate ORR mechanism of efficient chemical energy to electricity conversion.

Erratum to: On the voltage behavior of quantum dot light-emitting diode

Erratum to Nano Research,2023,16(4):5511–5516 https://doi.org/10.1007/s12274-022-5106-8 The title in the article was unfortunately mispresented on page 5511.The title of the article should be corrected to“On the voltage sweep behavior of quantum dot light-emitting diode”.Instead of On the voltage behavior of quantum dot light-emitting diode It should read On the voltage sweep behavior of quantum dot light-emitting diode.

Effect and mechanism of encapsulation on aging characteristics of quantum-dot light-emitting diodes

The aging characteristics,e.g.,the evolution of efficiency and luminance of quantum-dot light-emitting diodes(QLEDs)are greatly affected by the encapsulation.When encapsulated with ultraviolet curable resin,the efficiency is increased over time,a known phenomenon termed as positive aging which remains one of the unsolved mysteries.By developing a physical model and an analytical model,we identify that the efficiency improvement is mainly attributed to the suppression of hole leakage current that is resulted from the passivation of ZnMgO defects.When further encapsulated with desiccant,the positive aging effect vanishes.Tofully take the advantage of positive aging,the desiccant is incorporated after the positive aging process is completed.With the new encapsulation method,the QLED exhibits a high external quantum efficiency of 20.19%and a half lifetime of 1,267 h at an initial luminance of 2,800 cd·m^(-2),which are improved by 1.4 and 6.0 folds,respectively,making it one of the best performing devices.Our work provides an in-depth and systematic understanding of the mechanism of positive aging and offers a practical encapsulation way for realizing efficient and stable QLEDs.

Atomic-level correlation between the electrochemical performance of an oxygen-evolving catalyst and the effects of CeO_(2) functionalization

Herein,we prepared a bimetallic layered double hydroxide(FeCo LDH)featuring a dandelion-like structure.Anchoring of CeO_(2)onto FeCo LDH produced interfaces between the functionalizing CeO_(2)and the parent LDH.Comparative electrochemical studies were carried out.Onset potential,overpotential,and Tafel slope point to the superior oxygen-evolving performance of CeO_(2)-FeCo LDH with respect to FeCo LDH,therefore,demonstrating the merits of CeO_(2)functionalization.The electronic structures of Fe,Co,and Ce were analyzed by X-ray photoelectron spectroscopy(XPS)and electron energy loss spectroscopy(EELS)from which the increase of Co^(3+)and the concurrent lowering of Ce^(4+)were established.With the use of CeO_(2)-FeCo LDH,accelerated formation at a sizably reduced potential of Co-OOH,one of the key intermediates preceding the release of O_(2)was observed by in situ Raman spectroscopy.We now have the atomic-level and location-specific evidence,the increase of the active Co^(3+)across the interface to correlate the enhanced catalytic performance with CeO_(2)functionalization.

The influence of H_(2)O and O_(2) on the optoelectronic properties of inverted quantum-dot light-emitting diodes

The influence of H_(2)O and O_(2) on the performances of Mg-doped zinc oxide (ZnMgO) and ZnMgO-based inverted quantum-dot light-emitting diodes (QLEDs) are studied. With the involvement of H_(2)O from ambience, ZnMgO exhibits a high conductivity, whereas the resultant QLEDs show a low efficiency. The efficiency of QLEDs can be enhanced by annealing ZnMgO in H_(2)O-free glovebox;however, the uniformity and the current of the devices are degraded due to the presence of O_(2), which adsorbs on the surface of ZnMgO and captures the free electrons of ZnMgO. By exposing the devices with ultraviolet (UV) irradiation, the adsorbed O_(2) can be released, consequently leading to the increase of driving current. Our work discloses the influence of the annealing ambience on the conductivity of ZnMgO, and reveals the interaction of H_(2)O/O_(2) and UV with the ZnMgO and its effect on the performance of the resultant inverted QLEDs, which could help the community to better understand the mechanisms of ZnMgO-based QLEDs.

On the voltage behavior of quantum dot light-emitting diode

The origin of the efficiency drop of quantum dot light-emitting diode(QLED)under consecutive voltage sweeps is still a puzzle.In this work,we report the voltage sweep behavior of QLED.We observed the efficiency drop of red QLED with ZnMgO electron transport layer(ETL)under consecutive voltage sweeps.In contrast,the efficiency increases for ZnO ETL device.By analyzing the electrical characteristics of both devices and surface traps of ZnMgO and ZnO nanoparticles,we found the efficiency drop of ZnMgO device is related to the hole leakage mediated by trap state on ZnMgO nanoparticles.For ZnO device,the efficiency raise is due to suppressed electron leakage.The hole leakage also causes rapid lifetime degradation of ZnMgO device.However,the efficiency and lifetime degradation of ZnMgO device can be eliminated with shelf aging.Our work reveals the distinct voltage sweep behavior of QLED based on different ETLs and may help to understand the lifetime degradation mechanism in QLED.

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.

Anti-perovskite materials for energy storage batteries

Anti-perovskites X3BA,as the electrically inverted derivatives of perovskites ABX3,have attracted tremendous attention for their good performances in multiple disciplines,especially in energy storage batteries.The Li/Na-rich antiperovskite(LiRAP/NaRAP)solid-state electrolytes(SSEs)typically show high ionic conductivities and high chemical/electrochemical stability toward the Li-metal anode,illustrating their great potential for applications in the Limetal batteries(LMBs)using nonaqueous liquid electrolyte or all-solid-state electrolyte.The antiperovskites have been studied as artificial solid electrolyte interphase for Li-metal anode protection,film SSEs for thin-film batteries,and low melting temperature solid electrolyte enabling melt-infiltration for the manufacture of all-solid-state lithium batteries.Transition metal-doped LiRAPs as cathodes have demonstrated a high discharge specific capacity and good rate capability in the Li-ion batteries(LIBs).Additionally,the underlying scientific principles in antiperovskites with flexible structural features have also been extensively studied.In this review,we comprehensively summarize the development,structural design,ionic conductivity and ion transportation mechanism,chemical/electrochemical stability,and applications of some antiperovskite materials in energy storage batteries.The perspective for enhancing the performance of the antiperovskites is also provided as a guide for future development and applications in energy storage.

Influence of mixed organic cations on the nonlinear optical properties of lead tri-iodide perovskites

Metal halide perovskite materials have been widely studied recently due to their excellent optoelectronic properties.Among these materials,organic-inorganic hybrid perovskites have attracted much attention because of their relatively soft framework,which makes them more suitable for nonlinear optical(NLO)applications.However,there is rare physical mechanism study on the coexistence of two-photon absorption(TPA)and saturable absorption(SA)in organic-inorganic hybrid perovskite materials.To clarify this issue,the NLO properties of mixed cation perovskite MA1-xFAxPbI3[MA=CH3NH3,FA=CH(NH2)2,x=0,0.2,0.4,0.6,and 0.8]thin films are investigated in this paper.Based on the nonlinear transmittance and femtosecond-transient absorption spectrum measurements,it is found that the MA1-xFAxPbI3 materials exhibit NLO behavior dependent on excitation intensity.The TPA coefficient of MA1-xFAxPbI3 decreases with the increase of formamidinium(FA)content,while the relevant saturable intensity increases.In addition,it is revealed that the linear absorption process from valence band 2 to valance band 1 still exists even under a very low excitation intensity.With the increase of excitation intensity,the light transmittance at 1300 nm decreases first and then increases sharply,which also supports the explanation for the coexistence of TPA and SA.It is expected that our findings will promote the application of perovskite materials in nonlinear optoelectronic devices.

Flexible and tandem quantum-dot light-emitting diodes with individually addressable red/green/blue emission

Tandem quantum-dot light-emitting diodes(QLEDs)with multiple QLED elements vertically connected by the intermediate electrodes offer the advantages of high brightness and long lifetime.However,it is challenging to individually address each QLED element in conventional tandem structures.To address this challenge,here,transparent QLEDs built on flexible plastic substrates are developed as the building blocks for the tandem QLEDs.By vertically integrating a red,a green,and a blue transparent QLEDs with an ultraviolet glue,the resultant tandem QLED can emit separately controllable red/green/blue(R/G/B)emission with an external quantum efficiency(EQE)of 12.0%/8.5%/4.5%,respectively.Enabled by the transparent and extractable IZO electrodes,the QLED elements can also be connected in series or in parallel with an EQE of 24.8%or 8.2%,respectively.Our work provides a new implementation strategy for the realization of tandem QLEDs with individually addressable R/G/B emission for both display and lighting applications.

CdSe/CdS纳米晶在壳层形成和生长过程中的形貌调控:表面配体对晶体结构的决定性作用

CdSe/CdS纳米晶是研究最多的半导体纳米晶之一,然而,仍有许多方面有待研究.本文中,我们揭示了核-壳纳米晶的形貌主要由表面配体和核心浓度控制,而非核心的晶体结构.其中,羧酸镉促进各向同性结构的生长,而相反地,长链膦酸镉有利于各向异性结构的制备.对于蝌蚪形貌纳米晶,羧酸镉对于头部壳层影响较大,而膦酸镉在各向异性尾部生长中起主要作用.与预期相反, CdSe核心的晶体结构(闪锌矿或纤锌矿)在决定最终的晶体形貌方面几乎没有作用,这可能是由于CdS壳层两个阶段的生长,并导致了蝌蚪形貌的生成.通过选择恰当的表面配体,可以在CdSe/CdS核壳结构形成和生长过程中精确地调控其形貌.在本工作中,蝌蚪、纳米花、点-棒结构、多足结构均可以通过调控表面配体的比率而获得.这种独特的晶体生长机制可以应用于其他基于种子生长的工艺以构筑各向异性纳米结构.

Achieving better aqueous rechargeable zinc ion batteries with heterostructure electrodes

Aqueous rechargeable zinc ion batteries(ARZIBs)have received unprecedented attention owing to the low cost and high-safety merits.However,their further development and application are hindered by the issues of electrodes such as cathode dissolution,zinc anode dendrite,passivation,as well as sluggish reaction kinetics.Designing heterostructure electrodes is a powerful method to improve the electrochemical performance of electrodes by grafting the advantages of functional materials onto the active materials.In this review,various modified heterostructure electrodes with optimized electrochemical performance and wider applications are introduced.Moreover,the synergistic effect between active materials and functional materials are also in-depth analyzed.The specific modification methods are divided into interphase modification(electrode-electrolyte interphase and electrode-current collector interphase)and structure optimization.Finally,the conclusion and future perspective on the optimization mechanism of functional materials,and the cost issue of practical heterostructure electrodes in ARZIBs are also proposed.It is expected that this review can promote the further development of ARZIBs towards practical utility.

Highly efficient transparent quantum-dot light-emitting diodes based on inorganic double electron-transport layers

Herein,we report the fabrication of high-performance transparent quantum-dot light-emitting diodes(Tr-QLEDs)with ZnO/ZnMgO inorganic double electron-transport layers(ETLs).The ETLs effectively suppress the excess electron injection and facilitate charge balance in the Tr-QLEDs.The thick ETLs as buffer layers can also withstand the plasma-induced damage during the indium tin oxide sputtering.These factors collectively contribute to the development of Tr-QLEDs with improved performance.As a result,our Tr-QLEDs with double ETLs exhibited a high transmittance of 82%at 550 nm and a record external quantum efficiency of 11.8%,which is 1.27 times higher than that of the devices with pure ZnO ETL.These results indicate that the developed ZnO/ZnMgO inorganic double ETLs could offer promising solutions for realizing high-efficiency Tr-QLEDs for next-generation display devices.

原位绿色反溶剂法钝化钙钛矿表界面缺陷提高钙钛矿太阳能电池效率和稳定性

目前钙钛矿太阳能电池多采用反溶剂成膜法制备钙钛矿吸收层,其优点是工艺简便、成本低廉.但是反溶剂法是一种快速结晶的制备方法,容易在钙钛矿薄膜晶粒的晶界和表面形成大量的缺陷,导致钙钛矿太阳能电池器件效率和稳定性的下降.虽然通过钙钛矿成膜之后再沉积钝化材料的后处理法可以钝化钙钛矿薄膜表面的缺陷,但是这种后处理法无法有效钝化晶粒界面处的缺陷.同时,由于目前多采用氯苯和甲苯等有毒溶剂作为反溶剂,制备过程产生的有毒污染较为严重.为了解决上述问题,本文将无毒的十六烷基三甲基氯化铵作为钝化剂直接加入无毒的异丙醇中作为绿色反溶剂,可以在钙钛矿晶体生长和成膜的过程中原位钝化晶粒的界面和表面的缺陷.通过这种原位钝化的方法,可以将钙钛矿太阳能电池器件的效率由20.3%提升至23.4%,并且稳定性也得到了明显提高.

Numerical Study on Surface Wettability Gradient Enhanced Ultra-Thin Loop Heat Pipe

Loop heat pipes(LHPs),as high-efficiency heat dissipation components,are considered to be superior thermal conductors beyond any known materials.To apply LHPs to mobile electronics,a small,thin and compact system needs to be designed.However,with the trend of miniaturization,the heat transfer performance of LHPs degrades rapidly due to the significant increase of working fluid backflow resistance.This work aims to propose an effective solution to this problem.In this work,the surface wettability gradient(SWG)is introduced into the ultra-thin LHP,and the influence of SWG on mass and heat transfer performance is studied comprehensively by using a transient three-dimensional numerical model.It is observed that the SWG can significantly increase the vapor-liquid circulation efficiency and improve heat transfer performance.Numerical experiments have been performed to compare the two kinds of LHPs with and without SWG.At the heat load of 4–6 W,the start-up time for LHP with SWG is shortened by 11.5%and the thermal resistance is reduced by about 44.3%,compared with the LHP without SWG.This work provides a solution for the performance-degradation problem caused by miniaturization,as a numerical reference for experiments.