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Perovskite solar cells (PSCs) comprise a solid perovskite absorber sandwiched between several layers of different charge-selective materials, ensuring unidirectional current flow and high voltage output of the devices1,2. A 'buffer material' between the electron-selective layer and the metal electrode in p-type/intrinsic/n-type (p-i-n) PSCs (also known as inverted PSCs) enables electrons to flow from the electron-selective layer to the electrode3-5. Furthermore, it acts as a barrier inhibiting the inter-diffusion of harmful species into or degradation products out of the perovskite absorber6-8. Thus far, evaporable organic molecules9,10 and atomic-layer-deposited metal oxides11,12 have been successful, but each has specific imperfections. Here we report a chemically stable and multifunctional buffer material, ytterbium oxide (YbOx), for p-i-n PSCs by scalable thermal evaporation deposition. We used this YbOx buffer in the p-i-n PSCs with a narrow-bandgap perovskite absorber, yielding a certified power conversion efficiency of more than 25%. We also demonstrate the broad applicability of YbOx in enabling highly efficient PSCs from various types of perovskite absorber layer, delivering state-of-the-art efficiencies of 20.1% for the wide-bandgap perovskite absorber and 22.1% for the mid-bandgap perovskite absorber, respectively. Moreover, when subjected to ISOS-L-3 accelerated ageing, encapsulated devices with YbOx exhibit markedly enhanced device stability.
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Surface ligand chemistry is vital to control the synthesis, diminish surface defects, and improve the electronic coupling of quantum dots (QDs) toward emerging applications in optoelectronic devices. Here, we successfully develop highly homogeneous and dispersed AgBiS2 QDs, focus on the control of interdot spacing, and substitute the long-chain ligands with ammonium iodide in solution. This results in improved electronic coupling of AgBiS2 QDs with excellent surface passivation, which greatly facilitates carrier transport within the QD films. Based on the stable AgBiS2 QD dispersion with the optimal ligand state, a homogeneous and densely packed QD film is prepared by a facile one-step coating process, delivering a champion power conversion efficiency of approximately 8% in the QD solar cells with outstanding shelf life stability. The proposed surface engineering strategy holds the potential to become a universal preprocessing step in the realm of high-performance QD optoelectronic devices.
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As the initial synthesized colloidal quantum dots (CQDs) are generally capped with insulating ligands, ligand exchange strategies are essential in the fabrication of CQD films for solar cells, which can regulate the surface chemical states of CQDs to make them more suitable for thin-film optoelectronic devices. However, uncontrollable surface adsorption of water molecules during the ligand exchange process introduces new defect sites, thereby impairing the resultant device performance, which attracts more efforts devoted to it but remains a puzzle. Here, we develop a solvent-engineering-assisted ligand exchange strategy to revamp the surface adsorption, improve the exchange efficiency, and modulate the surface chemistry for the environmentally friendly lead-free silver bismuth disulfide (AgBiS2) CQDs. The optimized AgBiS2 CQD solar cells deliver an outstanding champion power conversion efficiency (PCE) of up to 8.95% and improved long-term stability. Our strategy is less environment-dependent and can produce solar cells with negligible performance variance for several batches across several months. Our work demonstrates the critical role of solvents for ligand exchange in the surface chemistry of CQDs and the realization of high-performance photovoltaic devices in a highly reproducible manner.
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The benefits of excess PbI2 on perovskite crystal nucleation and growth are countered by the photoinstability of interfacial PbI2 in perovskite solar cells (PSCs). Here we report a simple chemical polishing strategy to rip PbI2 crystals off the perovskite surface to decouple these two opposing effects. The chemical polishing results in a favorable perovskite surface exhibiting enhanced luminescence, prolonged carrier lifetimes, suppressed ion migration, and better energy level alignment. These desired benefits translate into increased photovoltages and fill factors, leading to high-performance mesostructured formamidinium lead iodide-based PSCs with a champion efficiency of 24.50%. As the interfacial ion migration paths and photodegradation triggers, dominated by PbI2 crystals, were eliminated, the hysteresis of the PSCs was suppressed and the device stability under illumination or humidity stress was significantly improved. Moreover, this new surface polishing strategy can be universally applicable to other typical perovskite compositions.
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Peregrine rogue wave excitation has applications in gaining high-intensity pulses, etc., and a high-order rogue wave exhibits higher intensity. An exact solution and collision between breathers are two existing ways to excite high-order ones. Here we numerically report a new, to the best of our knowledge, possible method, which is by multi-Gaussian perturbations on a continuous wave. The order and maximal intensity of rogue waves can be adjusted by the number of perturbations. The maximal intensity approaches 63.8 times that of the power of the initial background wave, and it retains a large value under the influence of fiber loss and noise. Our results provide guidance in gaining high-intensity pulses in experiment and understanding the universality of rogue wave generation.
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We study numerically the evolutions of perturbations at critical points between modulational instability and stability regimes. It is demonstrated that W-shaped solitons and rogue waves can be both excited from weak resonant perturbations at the critical points. The rogue wave excitation at the critical points indicates that rogue wave comes from modulation instability with resonant perturbations, even when the baseband modulational instability is absent. The perturbation differences for generating W-shaped solitons and rogue waves are discussed in detail. These results can be used to generate W-shaped solitons and rogue waves controllably from weak perturbations.
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Aiming at the problem of indoor environment, signal non-line-of-sight propagation and other factors affect the accuracy of indoor locating, an algorithm of indoor fingerprint localization based on the eight-neighborhood template is proposed. Based on the analysis of the signal strength of adjacent reference points in the fingerprint database, the methods for the eight-neighborhood template matching and generation were studied. In this study, the indoor environment was divided into four quadrants for each access point and the expected values of the received signal strength indication (RSSI) difference between the center points and their eight-neighborhoods in different quadrants were chosen as the generation parameters. Then different templates were generated for different access points, and the unknown point was located by the Euclidean distance for the correlation of RSSI between each template and its coverage area in the fingerprint database. With the spatial correlation of fingerprint data taken into account, the influence of abnormal fingerprint on locating accuracy is reduced. The experimental results show that the locating error is 1.0 m, which is about 0.2 m less than both K-nearest neighbor (KNN) and weighted K-nearest neighbor (WKNN) algorithms.
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We investigate linear interference effects between a nonlinear plane wave and bright solitons, which are admitted by a pair-transition coupled two-component Bose-Einstein condensate. We demonstrate that the interference effects can induce several localized waves possessing distinctive wave structures, mainly including anti-dark solitons, W-shaped solitons, multi-peak solitons, Kuznetsov-Ma like breathers, and multi-peak breathers. Specifically, the explicit conditions for them are clarified by a phase diagram based on the linear interference properties. Furthermore, the interactions between these localized waves are discussed. The detailed analysis indicates that the soliton-soliton interaction induced phase shift brings the collision between these localized waves which can be inelastic for solitons involving collision and can be elastic for breathers. These characters come from the fact that the profile of solitons depends on the relative phase between bright solitons and a plane wave, and the profile of breathers does not depend on the relative phase. These results would motivate more discussions on linear interference between other nonlinear waves. Specifically, the solitons or breathers obtained here are not related to modulational instability. The underlying reasons are discussed in detail. In addition, possibilities to observe these localized waves are discussed in a two species Bose-Einstein condensate.
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In many optoelectronic applications, patterning is required for functional and/or aesthetic purposes. However, established photolithographic technique cannot be applied directly to the hybrid perovskites, which are considered as promising candidates for optoelectronic applications. In this work, a wettability-assisted photolithography (WAP) process, which employs photolithography and one-step solution process to deposit hybrid perovskite, was developed for fabricating patterned hybrid perovskite films. Uniform pinhole-free hybrid perovskite films with sharp-edged micropatterns of any shapes can be constructed through the WAP process. Semitransparent solar cells with an adjustable active layer average visible transmittance of a wide range from 20.0% to 100% and regular solar cells based on patterned CH3NH3PbI3 perovskite films were fabricated to demonstrate that the WAP process was compatible with the manufacturing process of optoelectronic devices. With the widely equipped photolithographic facilities in the modern semiconductor industry, we believe the WAP process have a great potential in the industrial production of functionally or aesthetically patterned hybrid perovskite devices.
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We study optical rogue waves (RWs) in a nonlinear graded-index waveguide with variable coefficients. An exact RW solution on Gaussian background beam is presented, in contrast to the previous studies about RWs, on plane wave background. It is shown that the characteristics of RWs are maintained on Gaussian background beam and that the beam's width is even a bit smaller than the RWs scale. These results may raise the possibility of related experiments and potential applications in nonlinear optics.
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The catalytic capabilities of metals in degrading azo dyes have garnered extensive interest; however, selecting highly efficient metals remains a significant challenge. We have developed a Zn-Ca-based metallic glass composite which shows outstanding degradation efficiency for Direct Blue 6. This alloy comprises a Zn2Ca crystalline phase and an amorphous matrix, allowing for the degradation of azo dyes within minutes in a wide temperature range of 0-60 °C. Kinetic calculations reveal an exceptionally low activation energy of 8.99 kJ/mol. The rapid degradation is attributed to the active element Ca and the unique amorphous structure of the matrix, which not only facilitates abundant redox conditions but also minimizes the hydrolysis of the active element. The newly developed metallic glass composite exhibits a notably higher azo dye degradation rate compared to those of general metallic glasses, offering a new avenue for the rapid degradation of azo dyes. This paper holds significant importance for the development of novel azo dye wastewater treatment agents.
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The limited conductivity of existing transparent conducting oxide (TCO) greatly restricts the further performance improvement of perovskite solar cells (PSCs), especially for large-area devices. Herein, buried-metal-grid tin-doped indium oxide (BMG ITO) electrodes are developed to minimize the power loss caused by the undesirable high sheet resistance of TCOs. By burying 140-nm-thick metal grids into ITO using a photolithography technique, the sheet resistance of ITO is reduced from 15.0 to 2.7 Ω sq-1 . The metal step of BMG over ITO has a huge impact on the charge carrier transport in PSCs. The PSCs using BMG ITO with a low metal step deliver power conversion efficiencies (PCEs) significantly better than that of their counterparts with higher metal steps. Moreover, compared with the pristine ITO-based PSCs, the BMG ITO-based PSCs show a smaller PCE decrease when scaling up the active area of devices. The parallel-connected large-area PSCs with an active area of 102.8 mm2 reach a PCE of 22.5%. The BMG ITO electrodes are also compatible with the fabrication of inverted-structure PSCs and organic solar cells. The work demonstrates the great efficacy of improving the conductivity of TCO by BMG and opens up a promising avenue for constructing highly efficient large-area PSCs.
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Perovskite light-emitting diodes (PeLEDs) are the next promising display technologies because of their high color purity and wide color gamut, while two classical emitter forms, i.e., polycrystalline domains and quantum dots, are encountering bottlenecks. Weak carrier confinement of large polycrystalline domains leads to inadequate radiative recombination, and surface ligands on quantum dots are the main annihilation sites for injected carriers. Here, pinpointing these issues, we screened out an amphoteric agent, namely, 2-(2-aminobenzoyl)benzoic acid (2-BA), to precisely control the in situ growth of FAPbI3 (FA: formamidine) nanodomains with enhanced space confinement, preferred crystal orientation, and passivated trap states on the transport-layer substrate. The amphoteric 2-BA performs bidentate chelating functions on the formation of ultrasmall perovskite colloids (<1 nm) in the precursor, resulting in a smoother FAPbI3 emitting layer. Based on monodispersed and homogeneous nanodomain films, a near-infrared PeLED device with a champion efficiency of >22% plus enhanced T80 operational stability was achieved. The proposed perovskite nanodomain film tends to be a mainstream emitter toward the performance breakthrough of PeLED devices covering visible wavelengths beyond infrared.
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High-quality perovskite films are essential for achieving high performance of optoelectronic devices; However, solution-processed perovskite films are known to suffer from compositional and structural inhomogeneity due to lack of systematic control over the kinetics during the formation. Here, the microscopic homogeneity of perovskite films is successfully enhanced by modulating the conversion reaction kinetics using a catalyst-like system generated by a foaming agent. The chemical and structural evolution during this catalytic conversion is revealed by a multimodal synchrotron toolkit with spatial resolutions spanning many length scales. Combining these insights with computational investigations, a cyclic conversion pathway model is developed that yields exceptional perovskite homogeneity due to enhanced conversion, having a power conversion efficiency of 24.51% for photovoltaic devices. This work establishes a systematic link between processing of precursor and homogeneity of the perovskite films.
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Nickel and cobalt oxides are promising electrode materials for supercapacitors, but their poor conductivity and sluggish kinetics seriously hinder their application. Herein, a simple one-step calcination method was proposed to prepare carbon-incorporated NiO@Co3O4 (denoted as CNC) using a NiCo Prussian blue analogue (NiCo-PBA) as a precursor. The effect of calcination temperature on the electrochemical behavior of CNC was investigated. Benefiting from the relatively large specific surface area and porous structure characteristics, when used as an electrode for supercapacitors, the CNC obtained at 400 °C shows the typical features of a battery-type electrode, with a good specific capacitance of 208.5 F g-1 at 1 A g-1 and a rate capability of 70.8% at 30 A g-1. The hybrid supercapacitor (HSC) constructed with the optimum CNC electrode can provide a high energy density of 32.6 Wh kg-1 at the corresponding power density of 750.0 W kg-1 and an excellent cycling stability of 87.1% over 5000 cycles. This study provides a simple calcination method for preparing MOF-derived high-conductivity mixed metal oxide electrode materials for supercapacitors.
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To solve the problem of the low coercivity of Nd-Fe-B-based nanowires impeding their application in magnetic storage media, highly ordered Nd-Fe-B/Fe-Co composite nanowires were fabricated in an anodic alumina template by means of the alternating electrochemical deposition method. In this paper, the effect of soft and hard magnetic phase compositing on the magnetic properties of Nd-Fe-B-based nanowires was investigated, and the coercivity improvement mechanism was demonstrated. The results show that after annealing at 600 °C for 2 h, Nd-Fe-B/Fe-Co nanowires crystallize into a multiphase structure containing a hard Nd2(Fe, Co)14B phase and soft NdB4, NdB6, Fe7Nd, and Fe7Co3 phases. It is characterized that the Nd2(Fe, Co)14B phase preferentially nucleates, followed by NdB4 + NdB6 + Fe7Nd, while Fe7Co3 has been formed in as-deposited nanowires. The existence of a Nd2(Fe, Co)14B phase with high anisotropy fields, the remanence enhancement effect produced by exchange coupling between hard-soft magnetic phases, and the pinning effect between different phases make the composite nanowires approximately exhibit single hard magnetic phase characteristics with coercivity and remanence ratio as high as 4203.25 Oe and 0.89. The results indicate that synthesizing Nd-Fe-B/Fe-Co exchange-coupled composite nanowires via alternating electrodeposition is an effective way to optimize the magnetic performance of Nd-Fe-B-based nanowires.
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In recent years, Zn and its alloys have become some of the most promising degradable metals as in vivo implants due to their acceptable biocompatibility and more suitable degradation rate compared with Mg-based and Fe-based alloys. However, the degradation rate of Zn-based materials after implantation in the body for orthopedic applications is relatively slow, leading to long-term retention of the implants after fulfilling their missions. Moreover, the excessive release of Zn2+ during the degradation process of Zn-based implants usually leads to high cytotoxicity and delayed osseointegration. To provide a feasible solution to the problem faced by Zn-based implants, a Zn-Ca composite was fabricated by an air pressure infiltration method in this work. The XRD pattern of the composite suggests that the composite is fully composed of Zn-Ca intermetallic compounds. The degradation tests in vitro show that the composite has a much higher degradation rate than pure Zn, and the high Ca content regions in the composite can preferentially degrade as sacrificial anodes. In addition, the composite can efficiently induce Ca-P deposition during immersion tests in Hank's solution. Cytotoxicity tests indicate that L-929 cells exhibit around 82% cell viability (Grade 1) even after being cultured in the 100% extract prepared from the Zn-Ca composite for 1 day and show excellent cell viability.
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Ti-based bulk metallic glass (BMG) alloys have attracted widespread attention due to their strong glass forming ability, high specific strength, and good corrosion resistance. However, the poor plasticity of BMGs limits their further application in the aerospace and aircraft fields, as well as others. We optimized the composition of SiC-reinforced, Ti-based metallic glass matrix composites (MGMCs) through finite element modeling (FEM). FEM of MGMCs containing irregularly shaped SiC particles with different contents was conducted. Stress and strain analyses were conducted to evaluate the effect of the particle volume fraction on the mechanical behavior of MGMCs, and an optimization value of 30% was obtained, which is conducive to plasticity improvement. Arc melting copper mold injection casting was used to verify the optimized SiC content. The results show that the electroless nickel plating treatment effectively improves the wettability between SiC particles and the amorphous matrix, enabling the successful preparation of SiC/MGMC with a volume fraction of 29.5% through traditional injection casting. The volume fraction of SiC plays a crucial role in the transition of fracture mode from splitting to shear in MGMCs. After adding lightweight SiC particles, the yield strength, plasticity, modulus, and specific strength were improved by 25%, 1471%, 46%, and 33%, indicating that the use of nickel-plated SiC particles in MGMCs is an effective strengthening and toughening method for BMGs.
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The development of novel antibacterial nano-materials with synergistic biological effects has attracted extensive interest of the researchers. In the study, 0.5 mol% Ag and 0.5 mol% Cu co-doped K2Ti6O13(0.5 Ag-0.5 Cu-KTO) nanomaterial was successfully synthesized using two-step method of sol-gel and hydrothermal synthesis. The crystal structure of 0.5 Ag-0.5 Cu-KTO was the same as that of monoclinic K2Ti6O13. Ag ions and Cu ions were uniformly loaded on K2Ti6O13by replacing partial Ti ions, so that these antibacterial ions could be slowly released. High specific surface area of 0.5 Ag-0.5 Cu-KTO (337.6 m2g-1) provided more surface active sites for Ag-Cu doping and adsorption. More negative surface zeta potential (-32.83 mV in phosphate buffer solution and -21.45 mV in physiological saline solution, respectively) would be beneficial to prevent the aggregation of the nanowires in physiological environment. Under the same doping amount, compared to 1.0 mol% Cu doped K2Ti6O13, 0.5 Ag-0.5 Cu-KTO exhibited better antibacterial performance against gram-positive and gram-negative bacteria at only 100 µg ml-1dose concentration, near to 1.0 mol% Ag doped K2Ti6O13(1.0 Ag-KTO). And 0.5 Ag-0.5 Cu-KTO showed more excellent biocompatibility than 1.0 Ag-KTO, which was attribute to the introduction of Cu ions effectively decreasing the hemolytic and cytotoxic risks from Ag ions. As expected, the synthesized 0.5 Ag-0.5 Cu-KTO nanowires demonstrated excellent structural stability, high antibacterial activity, good hemocompatibility and cytocompatibility owing to the synergistic effects of Cu and Ag ions. 0.5 Ag-0.5 Cu-KTO nanowires will be a promising antimicrobial candidate for biomedical applications.
Assuntos
Antibacterianos , Nanofios , Antibacterianos/química , Titânio/química , Bactérias Gram-Negativas , Bactérias Gram-Positivas , ÍonsRESUMO
Solar cells capable of light-harvesting during daytime and light-emission at night are multifunctional semiconductor devices with many potential applications. Here, it is reported that halide perovskite heterojunction interfaces can be refined to yield stable and efficient solar cells. The cell can also operate effectively as an ultralow-voltage light-emitting diode (LED) with a peak external quantum efficiency of electroluminescence (EQEEL ) of 3.3%. Spectroscopic and microscopic studies reveal that double-heterojunction refinement with wide-bandgap salts is key to densifying the packing of perovskite grains and enlarging the bandgaps of the perovskite surfaces that are in contact with charge-transport semiconductors. The refined perovskite enables a simple device with dual actions of solar cells and LEDs. This type of all-in-one device has the potential to be used in multifunctional harvesting-storage-utilization (HSU) systems.