Microwave-Assisted Confining Growth and Liquid Exfoliation of sp^(3)-Hybrid Carbon Nitride Nano/Micro-Crystals

As one promising carbon-based material,sp^(3)-hybrid carbon nitride has been predicted with various novel physicochemical properties.However,the synthesis of sp^(3)-hybrid carbon nitride is still limited by the nanaoscale,low crystallinity,complex source,and expensive instruments.Herein,we have presented a facile approach to the sp^(3)-hybrid carbon nitride nano/micro-crystals with microwave-assisted confining growth and liquid exfoliation.Actually,the carbon nitride nano/micro-crystals can spontaneously emerge and grow in the microwave-assisted polymerization of citric acid and urea,and the liquid exfoliation can break the bulk disorder polymer to retrieve the highly crystalline carbon nitride nano/micro-crystals.The obtained carbon nitride nano/micro-crystals present superior blue light absorption strength and surprising photoluminescence quantum yields of 57.96% in ethanol and 18.05%in solid state.The experimental characterizations and density functional theory calculations reveal that the interface-trapped localized exciton may contribute to the excellent intrinsic light emission capability of carbon nitride nano/micro-crystals and the interparticle staggered stacking will prevent the aggregation-caused-quenching partially.Finally,the carbon nitride nano/micro-crystals are demonstrated to be potentially useful as the phosphor medium in light-emitting-diode for interrupting blue light-induced eye damage.This work paves new light on the synthesis strategy of sp^(3)-hybrid carbon nitride materials and thus may push forward the development of multiple carbon nitride research.

Efficient Semi‑Transparent Wide‑Bandgap Perovskite Solar Cells Enabled by Pure‑Chloride 2D‑Perovskite Passivation

Wide-bandgap(WBG)perovskite solar cells suffer from severe non-radiative recombination and exhibit relatively large opencircuit voltage(V_(OC))deficits,limiting their photovoltaic performance.Here,we address these issues by in-situ forming a well-defined 2D perovskite(PMA)_(2)PbCl_(4)(phenmethylammonium is referred to as PMA)passivation layer on top of the WBG active layer.The 2D layer with highly pure dimensionality and halide components is realized by intentionally tailoring the side-chain substituent at the aryl ring of the post-treatment reagent.First-principle calculation and single-crystal X-ray diffraction results reveal that weak intermolecular interactions between bulky PMA cations and relatively low cation-halide hydrogen bonding strength are crucial in forming the well-defined 2D phase.The(PMA)_(2)PbCl_(4)forms improved type-I energy level alignment with the WBG perovskite,reducing the electron recombination at the perovskite/hole-transport-layer interface.Applying this strategy in fabricating semi-transparent WBG perovskite solar cells(indium tin oxide as the back electrode),the V_(OC)deficits can be reduced to 0.49 V,comparable with the reported state-of-the-art WBG perovskite solar cells using metal electrodes.Consequently,we obtain hysteresis-free 18.60%-efficient WBG perovskite solar cells with a high V_(OC)of 1.23 V.

电泳法制备的致密氧化锡薄膜及其在高稳定性钙钛矿太阳能电池中的应用

在平面型钙钛矿太阳能电池中常采用SnO_(2)作为电子传输层材料,相应的SnO_(2)薄膜常采用溶液旋涂法制备。但是由于前驱液中的纳米颗粒可能会发生部分团聚、基底和溶液难以完全避免灰尘等杂质颗粒混入,且最佳的SnO_(2)电子传输层的厚度通常仅有约20 nm,所以这种方法制备的电子传输层难以保证严格致密和无纳米针孔。在本工作中,我们报道了一种电泳沉积制备致密SnO_(2)薄膜的方法,并用其有效地提高了钙钛矿太阳能电池的光电转换效率和工况稳定性。通过电泳法,表面带负电荷的SnO_(2)纳米颗粒在电场的作用下沉积到氧化铟锡(ITO)阳极表面,这种方法得到的薄膜比旋涂法制备的更为致密。将其应用于n-i-p结构的钙钛矿太阳能电池中,能够使得暗电流降低并抑制载流子的非辐射复合,从而提高电池的短路电流和开路电压,进而实现更高的光电转换效率(从18.17%提高到19.52%),且能消除迟滞效应。更重要的是,长期工况稳定性测试表明基于电泳-旋涂法制备的器件在1个太阳的光照下、最大功率点处连续工作960 h后,仍然能够保持71%的初始效率;然而基于旋涂法制备的器件在工作100 h后即降低到初始效率的70%。本工作提供了一种全新的SnO_(2)电子传输层的制备方法,显著地提高了器件性能和工况稳定性,后续有望应用于制备大面积器件和电池模组。

Observation and analysis of morphology abnormalities in development of Oryzias melastigma embryos

Fish embryos are widely used as models in toxicology,drug development,and human disease research because of their high sensitivity,observability,and operability,providing the basis for an in-depth understanding of the embryogenesis.Increasing studies have indicated that birth defects are hereditary.In this study,we used Oryzias melastigma as a model to conduct a study of 185-day embryogenesis and observed self-induced non-pathological abnormal embryogenesis.O.melastigma experienced pre-puberty stage,adolescence stage,and senescence stage,and individuals produced up to 102 eggs per day.However,the fecundity was markedly reduced during the senescent stage.During the active egg and blastodisc stages,pseudo-fertilization and pseudo-blastocysts were observed.During cleavage at the 4-to 32-cell stages,we observed blastomeres separation or dislocation.Excessively separated blastomeres formed double blastoderms,eventually resulting in conjoined twins.During the blastula stage,we observed abnormally increased cell volume,narrowed and elongated blastocysts,and abnormally coated blastoderms.At the organogenesis stage,we observed abnormal numbers of Kupff er’s vesicles and conjoined twins.Abnormality in the location and number of oil droplets were observed in various development stages.Abnormal development was more commonly observed in fertilized eggs produced by broodstock in pre-puberty or senescence stages,which is probably related to the age of fish and the egg quality.This study can provide the materials for comparative analysis in toxicological and molecular studies of O.melastigma,and may provide evidence for other economic fish that produce sticky eggs.

Sputtered SnO_(2)as an interlayer for efficient semitransparent perovskite solar cells

SnO_(2)is widely used as the electron transport layer(ETL)in perovskite solar cells(PSCs)due to its excellent electron mobility,low processing temperature,and low cost.And the most common way of preparing the SnO_(2)ETL is spincoating using the corresponding colloid solution.However,the spin-coated SnO_(2)layer is sometimes not so compact and contains pinholes,weakening the hole blocking capability.Here,a SnO_(2)thin film prepared through magnetron-sputtering was inserted between ITO and the spin-coated SnO_(2)acted as an interlayer.This strategy can combine the advantages of efficient electron extraction and hole blocking due to the high compactness of the sputtered film and the excellent electronic property of the spin-coated SnO_(2).Therefore,the recombination of photo-generated carriers at the interface is significantly reduced.As a result,the semitransparent perovskite solar cells(with a bandgap of 1.73 eV)based on this double-layered SnO_(2)demonstrate a maximum efficiency of 17.7%(stabilized at 17.04%)with negligible hysteresis.Moreover,the shelf stability of the device is also significantly improved,maintaining 95%of the initial efficiency after 800-hours of aging.

Sputtering under Mild Heating Enables High-Quality ITO for Efficient Semi-Transparent Perovskite Solar Cells

Semi-transparent perovskite solar cells(ST-PSCs)are promising in building-integrated photovoltaics(BIPVs)and tandem solar cells(TSCs).One of the keys to fabricate high-performance ST-PSCs is depositing efficient transparent electrodes.Indium tin oxide(ITO)is an excellent transparent conductive oxide with good light transmittance and high conductivity.However,the high sheet resistance of ITO sputtered at room temperature leads to the low fill factor(FF)and poor power conversion efficiency(PCE)of the ST-PSCs.Here,we study the effect of the sputtering temperature on the properties of ITO and the performance of ST-PSCs.We find that when the sputtering temperature increases from the room temperature to 70℃,the crystallinity of the sputtered ITO gradually improves.Therefore,the sheet resistance decreases and the corresponding device performance improves.However,once the sputtering temperature further increases over 70℃,the underlying hole transport layer will be damaged,leading to poor device performance.Therefore,the optimized mild heating temperature of 70℃is applied and we obtain ST-PSCs with a champion PCE of 15.21%.We believe this mild heating assisted sputtering method is applicable in fabricating BIPVs and TSCs.

基于北斗导航的智能棉花播种机设计与试验

根据沿海盐碱地饲草―短季棉连作种植模式的特点,设计一款新型的基于北斗导航的棉花智能播种机。该机具可一次完成北斗导航无人驾驶、播种带清整、种下分层施肥、种肥隔离、智能精量播种、种肥隔离、覆土镇压、地表塑形等工序。利用该机具进行田间试验,结果表明:作业后的衔接行准确,播行端直,提高了衔接行的精准度和播行的直线度,播深平均为2.8 cm;播深合格率为92.5%;衔接行间距精度为1.2 cm;播种行直线度为0.8 cm,土地利用率提高5%。为后续田间标准化作业奠定基础,实现播种施肥精准控制,节种节肥。

Anneal-free ultra-low loss silicon nitride integrated photonics

Heterogeneous and monolithic integration of the versatile low-loss silicon nitride platform with low-temperature materials such as silicon electronics and photonics,III–V compound semiconductors,lithium niobate,organics,and glasses has been inhibited by the need for high-temperature annealing as well as the need for different process flows for thin and thick waveguides.New techniques are needed to maintain the state-of-the-art losses,nonlinear properties,and CMOS-compatible processes while enabling this next generation of 3D silicon nitride integration.We report a significant advance in silicon nitride integrated photonics,demonstrating the lowest losses to date for an anneal-free process at a maximum temperature 250℃,with the same deuterated silane based fabrication flow,for nitride and oxide,for an order of magnitude range in nitride thickness without requiring stress mitigation or polishing.We report record low anneal-free losses for both nitride core and oxide cladding,enabling 1.77 dBm^(-1) loss and 14.9 million Q for 80 nm nitride core waveguides,more than half an order magnitude lower loss than previously reported sub 300℃ process.For 800 nm-thick nitride,we achieve as good as 8.66 dBm^(-1) loss and 4.03 million Q,the highest reported Q for a low temperature processed resonator with equivalent device area,with a median of loss and Q of 13.9 dBm^(-1) and 2.59 million each respectively.We demonstrate laser stabilization with over 4 orders of magnitude frequency noise reduction using a thin nitride reference cavity,and using a thick nitride micro-resonator we demonstrate OPO,over two octave supercontinuum generation,and four-wave mixing and parametric gain with the lowest reported optical parametric oscillation threshold per unit resonator length.These results represent a significant step towards a uniform ultra-low loss silicon nitride homogeneous and heterogeneous platform for both thin and thick waveguides capable of linear and nonlinear photonic circuits and integration with low-temperature materials and processes.

Stabilizing semi-transparent perovskite solar cells with a polymer composite hole transport layer

Semi-transparent perovskite solar cells(ST-PSCs)have broad applications in building integrated photovoltaics.However,the stability of ST-PSCs needs to be improved,especially in n-i-p ST-PSCs since the doped 2,2',7,7'-tetrakis(N,N-di-p-methoxyphenyl-amine)-9,9'-spirobifluorene(Spiro-OMeTAD)is unstable at elevated temperatures and high humidity.In this work,aπ-conjugated polymer poly[(2,6-(4,8-bis(5-(2-ethylhexyl)thiophene-2-yl)-benzo[1,2-b:4,5-b']dithiophene))-alt-(5,5-(1',3'-di-2-thienyl-5',7'-bis(2-ethylhexyl)benzo[1',2'-c:4',5'-c']dithiophene-4,8-dione)](PBDB-T)is selected to form a polymer composite hole transport layer(HTL)with Spiro-OMeTAD.The sulfur atom of the thiophene unit and the carbonyl group of the polymer interact with the undercoordinated Pb2+at the perovskite surface,which stabilizes the perovskite/HTL interface and passivates the interfacial defects.The incorporation of the polymer also increases the glass transition temperature and the moisture resistance of Spiro-OMeTAD.As a result,we obtain ST-PSCs with a champion efficiency of 13.71%and an average visible light transmittance of 36.04%.Therefore,a high light utilization efficiency of 4.94%can be obtained.Moreover,the encapsulated device can maintain 84%of the initial efficiency after 751 h under continuous one-sun illumination(at 30%relative humidity)at the open circuit and the unencapsulated device can maintain 80%of the initial efficiency after maximum power tracking for more than 1250 h under continuous one-sun illumination.

Tunable broadband two-point-coupled ultra-high-Q visible and near-infrared photonic integrated resonators

Ultra-high-quality-factor(Q)resonators are a critical component for visible to near-infrared(NIR)applications,including quantum sensing and computation,atomic timekeeping and navigation,precision metrology,microwave photonics,and fiber optic sensing and communications.Implementing such resonators in an ultra-low-loss CMOS foundry compatible photonic integration platform can enable the transitioning of critical components from the lab-to the chip-scale,such as ultra-low-linewidth lasers,optical reference cavities,scanning spectroscopy,and precision filtering.The optimal operation of these resonators must preserve the ultra-low losses and simultaneously support the desired variations in coupling over a wide range of visible and NIR wavelengths as well as provide tolerance to fabrication imperfections.We report a significant advancement in high-performance integrated resonators based on a two-point-coupling design that achieves critical coupling simultaneously at multiple wavelengths across wide wavebands and tuning of the coupling condition at any wavelength,from under-,through critically,to over-coupled.We demonstrate critical coupling at 698 nm and 780 nm in one visible-wavelength resonator and critical coupling over a wavelength range from 1550 nm to 1630 nm in a 340-million intrinsic Q 10-meter-coil waveguide resonator.Using the 340-million intrinsic Q coil resonator,we demonstrate laser stabilization that achieves six orders of magnitude reduction in the semiconductor laser frequency noise.We also report that this design can be used as a characterization technique to measure the intrinsic waveguide losses from 1300 nm to 1650 nm,resolving hydrogen-related absorption peaks at 1380 nm and 1520 nm in the resonator,giving insight to further reduce waveguide loss.The CMOS foundry compatibility of this resonator design will provide a path towards scalable system-on-chip integration for high-performance precision experiments and applications,improving reliability,and reducing size and cost.

Preparation of Perovskite Solar Cells in the Air:Degradation Mechanism and Prospects on Large-Area Fabrication

The preparation of perovskite solar cells(PsCs)in the air environment has attracted the attention of numerous experimenters due to its low preparation cost and the possibility of commercialization.Although the power conversion efficiency(PCE)of PSCs has increased rapidly and exceeded 25%,which is comparable to commercial polysilicon solar cells,most certified or reported high-efficiency perovskite solar cells are still confined to glove boxes or relatively small active areas in the air environment due to moisture,oxygen,high temperature,and ultraviolet(UV)factors.In this review.

Carbon Dots-in-Zeolite via In-Situ Solvent-Free Thermal Crystallization:Achieving High-Efficiency and Ultralong Afterglow Dual Emission

Organic afterglow materials are highly desirable for optoelectronic applications,but they usually suffer from complex preparation process,low quantum efficiency,and short lifetime due to the ultrafast deactivation of the highly active excited states involved.Here,we succeeded in achieving solventfree thermal syntheses of high-efficiency afterglow CDs@zeolite composite materials by simply grinding the solid raw materials of zeolite and precursor CDs at room temperature,followed by thermal crystallization.This method afforded maximum embedding of CDs into growing zeolite crystals,as well as strong host–guest interaction to surpass the nonradiative transition of CDs,thus producing composite materials with ultralong dual emission of thermally activated delayed fluorescence and room temperature phosphorescence with a record high lifetime of 1.7 and 2.1 s,respectively,and the quantum yield of 90.7%.Furthermore,in a preliminary experiment,we applied the composite materials in alternatingcurrent light-emitting diode supplementary lighting,which exhibited a promising potential in optoelectronic applications.

Lifetime-Engineered Phosphorescent Carbon Dots-in-Zeolite Composites for Naked-Eye Visible Multiplexing

Lifetime-coded optical multiplexing has attracted wide attention due to avoiding spectral overlap and background interference.At present,most of the materials used for lifetime-coded multiplexing involve rare-earth metal ions with their lifetime domains in the microsecond range,thus greatly limiting their application scope.

Near-infrared chemiluminescent carbon nanogels for oncology imaging and therapy

Carbon nanogels(CNGs)with dual ability of reactive oxygen species(ROS)imaging and photodynamic therapy have been designed with selfassembled chemiluminescent carbonized polymer dots(CPDs).With efficient deep-red/near-infrared chemiluminescence(CL)emission and distinctive photodynamic capacity,the H2O2-driven chemiluminescent CNGs are further designed by assembling the polymeric conjugate and CL donors,enabling an in vitro and in vivo ROS bioimaging capability in animal inflammation models and a high-performance therapy for xenograft tumors.Mechanistically,ROS generated in inflammatory sites or tumor microenvironment can trigger the chemically initiated electron exchange luminescence in the chemical reaction of peroxalate and H2O2,enabling in vivo CL imaging.Meanwhile,part of the excited-state electrons will transfer to the ambient H2O or dissolved oxygen and in turn lead to the type I and type II photochemical ROS production of hydroxyl radicals or singlet oxygen,endowing the apoptosis of tumor cells and thus enabling cancer therapy.These results open up a new avenue for the design of multifunctional nanomaterials for bioimaging and antienoplastic agents.

Pressure-induced photoluminescence enhancement and ambient retention in confined carbon dots

Piezochromic luminescent materials have shown great potential in advanced optoelectronic applications.However,most of luminescent materials usually undergo emission quenching under external stimuli.Herein,we demonstrate for the first time that the photoluminescence of carbon dots(CDs)confined within sodium hydroxide can be enhanced when high pressure is applied.They exhibit a 1.6-fold fluorescence enhancement compared with pristine CDs.Importantly,the enhanced fluorescence intensity can be retained after the release of pressure to ambient conditions.A combination of experimental analysis and theoretical simulations indicates that such an enhanced emission is mainly attributed to the strong confinement resulting from the sodium hydroxide matrix,which can separate the CDs spatially and restrict the nonradiative pathway.These results provide a rational strategy for manipulating the optical properties of CDs with enhanced and retainable photoluminescence(PL)performance,thus opening up a venue for designing luminescent CDs-based materials.

Efficient and stable inverted perovskite solar cells enabled by inhibition of self-aggregation of fullerene electron-transporting compounds

Fullerene-based electron-transporting layers(ETLs)significantly influence the defect passivation and device performance of inverted perovskite solar cells(PSCs).However,theπ-cage structures of fullerenes lead to a strong tendency to self-aggregate,which affects the long-term stability of the corresponding PSCs.Experimental results revealed that[6,6]-phenyl-C61-butyric acid methyl ester(PCBM)-based ETLs exhibit a certain degree of self-aggregation that affects the stability of the device,particularly under continuous irradiation stress.To modulate the aggregation behavior,we replaced a methyl hydrogen of PCBM with a phenyl group to yield[6,6]-phenyl-C61-butyric acid benzyl ester(PCBB).As verified through X-ray crystallography,this minor structural modification results in more non-covalent intermolecular interactions,which effectively enhanced the electron-transporting ability of the PCBB-based ETL and led to an efficiency approaching 20%.Notably,the enhanced intermolecular forces of PCBB suppressed its self-aggregation,and the corresponding device showed significantly improved stability,retaining approximately 90%of its initial efficiency after 600 h under one-sun irradiation with maximum power point tracking.These findings provide a viable approach for the design of new fullerene derivatives to tune their intermolecular interactions to suppress self-aggregation within the ETL for highperformance PSCs.

Monolithic bilayered In_(2)O_(3) as an efficient interfacial material for high-performance perovskite solar cells

Carrier recombination at the buried SnO_(2)/perovskite interface limits the efficiency and stability of n-i-p-structured perovskite solar cells(PSCs).Herein,we report an In_(2)O_(3)interfacial layer with the distinctive structure of the monolithic compact/nanostructured bilayer.The partial hydrolysis nature of the In^(3+)ion enables the formation of nanorods on top of the compact In_(2)O_(3)layer when spin-coating the In(NO_(3))_(3) aqueous solution.This novel interfacial layer reduces the pinholes of the SnO_(2)film and increases the contact area between the perovskite and electron transport material.Therefore,PSCs with the incorporation of the interfacial layer demonstrate enhanced electron extraction and suppressed carrier recombination.Consequently,the champion device achieves a power conversion efficiency of 23.87%with a high fill factor of 82.14%.The optimized device also shows robust operational stability,retaining over 80%of the initial power conversion efficiency after working at the maximum power point for over 500 h under continuous one-sun illumination.

Progress toward understanding the fullerene-related chemical interactions in perovskite solar cells

Fullerene materials have been widely used to fabricate efficient and stable perovskite solar cells(PSCs)due to their excellent electron transport ability,defect passivation effect,and beyond.Recent studies have shown that fullerene-related chemical interaction has played a crucial role in determining device performance.However,the corresponding fullerene-related chemical interactions are yet well understood.Herein,a comprehensive review of fullerene materials in regulating carrier transport,passivating the surface and grain boundary defects,and enhancing device stability is provided.Specifically,the influence of the fullerene-related chemical interactions,including fullerene-perovskite,fullerene-inorganic electron transport layer(IETL),and fullerene-fullerene,on the device performance is well discussed.Finally,we outline some perspectives for further design and application of fullerene materials to enhance the performance and commercial application of PSCs.

POSITIVE SOLUTIONS TO A BVP WITH TWO INTEGRAL BOUNDARY CONDITIONS

Based on the Guo-Krasnoselskii’s fixed-point theorem,the existence and multiplicity of positive solutions to a boundary value problem(BVP)with two integral boundary conditions{v(4)=f(s,v(s),v′(s),v〞(s)),s∈[0,1],v′(1)=v′'′(1)=0,v(0)=∫10 g1(T)v(T )dT ,v′′(0)=∫10 g2( T)v′′(T )d T}are obtained,where f,g1,g2 are all continuous.It generalizes the results of one positive solution to multiplicity and improves some results for integral BVPs.Moreover,some examples are also included to demonstrate our results as applications.

Multicolor biomass based carbon nanodots for bacterial imaging

Biomass-based carbon nanodots(CNDs) are becoming promising fluorescent materials due to their superior optical properties and excellent biocompatibility. However, most fluorescent CNDs are prepared under high temperatures with artificial chemicals as precursors. In this work, multicolor biomass-based CNDs have been prepared by employing natural biomass as precursors through an ultrasonic-assisted method at room temperature. The multicolor biomass-based CNDs can be prepared within 10 min, and cavitation produced by ultrasound in solution contributes to the polymerization of biomolecules into nanodots. The emission of the CNDs covers from blue to red region, with emission peaks centered at 410 nm, 520 nm and 670 nm, and the corresponding photoluminescence quantum yields of the CNDs are 11%, 12% and28%, respectively. Furthermore, bacterial imaging by using the biomass-based CNDs as fluorescent imaging agent has been demonstrated. This work provides a convenient ultrasonic-assisted way for fabrication multicolor and eco-friendly biomass CNDs, demonstrating their application in bacterial imaging.