Hole Alignment Research Articles

Relativistic treatment of hole alignment in noble gas atoms

The development in attosecond physics allows for unprecedented control of atoms and molecules in the time domain. Here, ultrashort pulses are used to prepare atomic ions in specific magnetic states, which may be important for controlling charge migration in molecules. Our work fills the knowledge gap of relativistic hole alignment prepared by femtosecond and attosecond pulses. The research focuses on optimizing the central frequency and duration of pulses to exploit specific spectral features, such as Fano profiles, Cooper minima, and giant resonances. Simulations are performed using the Relativistic Time-Dependent Configuration-Interaction Singles method. Ultrafast hole alignment with large ratios (on the order of one hundred) is observed in the outer-shell hole of argon. An even larger alignment (on the order of one thousand) is observed in the inner-shell hole of xenon.

Self-Polymerized Spiro-Type Interfacial Molecule toward Efficient and Stable Perovskite Solar Cells.

In the pursuit of highly efficient perovskite solar cells, spiro-OMeTAD has demonstrated recorded power conversion efficiencies (PCEs), however, the stability issue remains one of the bottlenecks constraining its commercial development. In this study, we successfully synthesize a novel self-polymerized spiro-type interfacial molecule, termed v-spiro. The linearly arranged molecule exhibits stronger intermolecular interactions and higher intrinsic hole mobility compared to spiro-OMeTAD. Importantly, the vinyl groups in v-spiro enable in situ polymerization, forming a polymeric protective layer on the perovskite film surface, which proves highly effective in suppressing moisture degradation and ion migration. Utilizing these advantages, poly-v-spiro-based device achieves an outstanding efficiency of 24.54 %, with an enhanced open-circuit voltage of 1.173 V and a fill factor of 81.11 %, owing to the reduced defect density, energy level alignment and efficient interfacial hole extraction. Furthermore, the operational stability of unencapsulated devices is significantly enhanced, maintaining initial efficiencies above 90 % even after 2000 hours under approximately 60 % humidity or 1250 hours under continuous AM 1.5G sunlight exposure. This work presents a comprehensive approach to achieving both high efficiency and long-term stability in PSCs through innovative interfacial design.

Self‐Polymerized Spiro‐Type Interfacial Molecule toward Efficient and Stable Perovskite Solar Cells

AbstractIn the pursuit of highly efficient perovskite solar cells, spiro‐OMeTAD has demonstrated recorded power conversion efficiencies (PCEs), however, the stability issue remains one of the bottlenecks constraining its commercial development. In this study, we successfully synthesize a novel self‐polymerized spiro‐type interfacial molecule, termed v‐spiro. The linearly arranged molecule exhibits stronger intermolecular interactions and higher intrinsic hole mobility compared to spiro‐OMeTAD. Importantly, the vinyl groups in v‐spiro enable in situ polymerization, forming a polymeric protective layer on the perovskite film surface, which proves highly effective in suppressing moisture degradation and ion migration. Utilizing these advantages, poly‐v‐spiro‐based device achieves an outstanding efficiency of 24.54 %, with an enhanced open‐circuit voltage of 1.173 V and a fill factor of 81.11 %, owing to the reduced defect density, energy level alignment and efficient interfacial hole extraction. Furthermore, the operational stability of unencapsulated devices is significantly enhanced, maintaining initial efficiencies above 90 % even after 2000 hours under approximately 60 % humidity or 1250 hours under continuous AM 1.5G sunlight exposure. This work presents a comprehensive approach to achieving both high efficiency and long‐term stability in PSCs through innovative interfacial design.

Numerical Investigation of Parameters Affecting Energy Losses in Multi-Stage Perforated Plates

Abstract Perforated plates are commonly used for flow control in pressurized systems. In different industrial applications, these devices are also used in series (multistage perforated plates) to manage high-pressure drop or reduce cavitation occurrence in industrial pipelines and enhance efficiency of gas turbines in power plants. In some specific conditions, the installation of perforated plates in series is a simple and cost-effective solution that increases plant efficiency. However, the large number of design parameters complicates the search for the optimal solution. With the aim of improving the knowledge of the most relevant design parameters, in the present investigation, the dissipation characteristics of multistage perforated plates are studied. Specifically, the analysis of the dependence of the pressure loss coefficient Eu on relative spacing and hole alignment for two subsequent identical plates is performed with CFD approach. Eight plates with different characteristics such as porosity, thickness, diameter, position, and number of holes are studied. The considered porosities vary in a range of 0.3–0.5, the ratio between plate thickness and hole diameter ranges between 0.7 and 1.3, and the number of holes between 4 and 26. A critical spacing between the plates, beyond which the pressure losses are independent of the alignment of the holes, has been calculated. The results obtained are relevant for a deeper understanding of the complex phenomenon of multistage perforated plates and can be used for the design and the installation of these devices commonly used in different engineering applications.

Self-woven monolayer polyionic mesh to achieve highly efficient and stable inverted perovskite solar cells

Poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) is widely used in inverted perovskite solar cells due to its simple preparation process, high stability and light transmittance (low refractive index and extinction coefficient). Theoretical studies have shown that a sufficiently thin PEDOT:PSS layer is necessary to guarantee high optical absorption of the devices. However, some limitations of PEDOT:PSS film induced by traditional deposition method, such as thick film, partly unfriendly contact at PEDOT:PSS/perovskite, hamper its progress in the inverted PSCs for a future market success. Here, a namely self-woven deposition method, has been proposed to prepare a pinhole-free monolayer PEDOT:PSS mesh. The Power conversion efficiency (PCE) of an inverted device has been boosted to 19.49 % from 15.31%, once employing this monolayer PEDOT:PSS mesh as hole transport layer, with structure of ITO/PEDOT:PSS/MAPbI3(Cl)/C60/BCP/Ag. The high performance is mainly attributed to more light reach to perovskite layer due to this monolayer polyionic mesh, and is secondarily ascribed to better energy-level alignment and efficient hole extraction. In addition, this monolayer mesh based device exhibits a relatively high operation stability as well as storage stability thanks to the reduction of the unpaired PSS. Particularly, the validity of the self-woven method is confirmed by employing (FASnI3)0.6(MAPbI3)0.4 perovskite as active material in the same scenario, achieving more than 21% PCE.

Efficient non-fullerene organic solar cells with low-temperature solution-processing ferrous oxides as hole transport layer

Abstract Non-fullerene organic solar cells (NF–OSCs) have recently attracted enormous attention due to the rapid advance of high-performance photoabsorbers. On the other hand, interfacial materials also play a crucial role in further increasing the device efficiency, but those materials in particular effective hole transporting ones for NF–OSCs are less developed. In this work, three low-temperature solution-processing ferrous oxide films (including CoOx, NiOx, and FeOx) are used as hole transporting layer (HTL) for NF–OSCs. By adding a surfactant and treating with the ultraviolet ozone (UVO), uniform ferrous oxide films with adjustable energy bands are achieved. The NF–OSCs based on PBDB-T-2Cl:IT-4F active layer and using CoOx, NiOx, and FeOx as the HTL afford power conversion efficiencies of 11.4%, 10.2% and 6.4%, respectively. The higher performance of NF–OSCs with the UVO-treated CoOx as the HTL is attributed to its more suitable energy level alignment and better hole transportation property relative to those of the other two counterparts.

Rational design of D–π–D hole-transporting materials for efficient perovskite solar cells

D–π–D hole-transporting materials are designed via facile approaches for efficient perovskite solar cells. Suitable band alignment and high hole mobility by strengthening the conjugation in the core allow effective hole extraction.

All-Inorganic Perovskite Solar Cells Using Treated Carbon Materials for Effective Charge Extraction

Perovskite solar cells (PSCs) have become the leader in the field of the third-generation solar cells due to their outstanding photovoltaic performance and low cost. However, the instability stemming from low tolerance to humidity and heat as well as residual solvents and ultraviolet illumination would be challenging for long-term stability. Recently, all inorganic perovskites, especially carbon-based hole-transporting material (HTM) CsPbBr3 perovskite, have attracted increasing attentions because of their enhanced moisture and thermal stability compared to hybrid counterparts.For the CsPbBr3 device, a challenging route to increase power conversion efficiency (PCE) is to take interfacial charge transfer into consideration and reduce interfacial energy-level differences to reduce space charge accumulation and enhance charge extraction. It is known that graphene-based derivatives are promising candidates for interfacial materials due to their excellent electronic properties. For example, graphene quantum dots (GQDs) between perovskite and TiO2 could significantly enhance the performance of PSCs due to dramatically enhanced electron extraction by the inserted GQDs; polyaniline/graphite composites were incorporated into carbon electrode to tailor work function and to improve hole-selectivity of back electrode for enhanced energy level alignment and interfacial hole extraction, leading to a remarkably reduced energy loss and charge recombination.Herein, we developed a strategy to use carbon dots (CDs) with tunable bandgaps and high absorption coefficients for electron extraction performance. The CDs were prepared by exfoliation method from oxidized graphite, and CDs in dimethylformamide solution were spin-coated onto FTO/c-TiO2/m-TiO2 substrate, then a multistep solution-processed method was used to prepare Cs-Pb-Br films with controllable CsPbBr3 phase. Specifically, CsBr/methanol solution (~15 mg mL-1) was spin-coated onto PbBr2 film and then annealed at 250 °C for 5 min, and the processes were repeated for 5 times. The obtained cesium lead bromide films were washed by 2-propanol. Finally, a carbon back-electrode with an average area of 0.09 cm2 was deposited onto the device. We fabricated all-inorganic PSCs with the FTO/c-TiO2/m-TiO2/CDs/CsPbBr3/carbon structure. Arising from the suppressed interfacial charge recombination, the optimal device yielded a PCE up to 10.67% under one sun illumination. These findings suggest that graphene-based derivatives can be used as interfacial modification materials toward high-performance carbon-based HTM-free PSCs.

Spiro‐Linked Molecular Hole‐Transport Materials for Highly Efficient Inverted Perovskite Solar Cells

Spiro‐linked compounds have been used as benchmark hole‐transport materials (HTMs) for the construction of efficient normal architecture (n‐i‐p) perovskite solar cells (PSCs). However, the heavy reliance on the use of dopants not only complicates the device fabrication but imposes long‐term stability concern of the devices. Herein, it is reported that solution‐processed dopant‐free spiro molecules can serve as superior HTMs to fabricate efficient inverted (p‐i‐n) PSCs. Rational choice of orthogonal solvent allows us to solution deposit uniform and pinhole‐free perovskite films without compromising the hole‐extraction capability of the spiro‐based interface layers. To illustrate the generality of the strategy, three spiro‐linked molecules are investigated side by side as HTMs in one‐step solution‐processed CH3NH3PbI3 PSCs. Due to the favored energy‐level alignment and high hole mobility, solar cells based on the HTM of spiro‐TTB yield a high efficiency of 18.38% with open‐circuit voltages (VOC) up to 1.09 V. These results suggest that small molecular HTMs commonly developed for normal structure devices can be of great potential to fabricate cost‐effective and highly efficient inverted PSCs.

Enhanced energy level alignment and hole extraction of carbon electrode for air-stable hole-transporting material-free CsPbBr3 perovskite solar cells

Carbon-based hole-transporting material (HTM)-free CsPbBr3 perovskite solar cells (PSCs) provide new opportunities for promoting the commercial application of PSCs because of the low cost, simple preparation process and excellent stability under various extreme conditions. One of the remaining problems for inorganic CsPbBr3 PSCs is the low power conversion efficiency (PCE) due to the large energy level difference and inefficient hole extraction at CsPbBr3/carbon interface. Herein, polyaniline/graphite (PANi/G) composites are incorporated into carbon electrode to tailor work function and to improve hole-selectivity of back electrode for enhanced energy level alignment and interfacial hole extraction, leading to a remarkably reduced energy loss and charge recombination. The HTM-free CsPbBr3 PSC based on carbon-PANi/G electrode achieves a PCE of 8.87%, which is increased by 43.8% in comparison with 6.17% for the control device. Moreover, the unencapsulated device shows excellent long-term moisture tolerance with the initial PCE maintaining 93.5% even exposure to air atmosphere with 80% RH at 25 °C over 50 days. The successful improvement of energy level alignment and charge extraction in device by directly incorporating PANi/G composites into carbon electrode offers a promising strategy in developing low-cost and efficient HTM-free PSCs.

Copper induced direct CO2 laser drilling blind hole with the aid of brown oxidation for PCB CCL

CO2 laser drilling of blind hole is the necessary process to obtain high-density connection between different conductive layers for printed circuit board (PCB). A copper induced direct CO2 laser drilling blind hole was proposed to simplify the working process and enhance hole alignment with the aid of copper brown oxidation. Brown oxidized copper holding a roughened surface to extend the laser route in its surface and copper oxidation of CuO with a high laser absorptivity were investigated by scanning electron microscopy (SEM), 3D microscope, X-ray photoelectron spectroscopy (XPS), infrared thermal camera, and metallographic microscopy. It therefore breaks the limitation of pure copper stripped by CO2 laser. Example for CCL of top copper with thickness of 18 μm and dielectric resin with thickness of 80 μm realized the qualified Φ100 μm blind hole under 45 mL/L brown oxidation solution for 90 s.

Failure investigation of in-flight separation of afterburner nozzle flap in a turbojet engine

Abstract A turbojet fighter experienced a separation of the afterburner nozzle flap during flight. Three mounting bolts were intended to fasten the nozzle flap assembly, but complete fracture of these bolts was the primary reason of failure. One of them was lost during the incident and two shank parts of the mounting bolts remained in the engine component. Laboratory investigation of the failed components of the nozzle flap assembly indicated that the mounting bolts were improperly installed during the last maintenance. Detailed fractographic study and metallurgical analysis focused on the fractured bolts and revealed fatigue striations with an overload dimple morphology in all fractured surfaces of the bolts. The investigation established sufficient evidence of improper installation of the primary flap assembly due to deformation of the alignment hole which inevitably resulted in higher operational loads on the bolt. It is concluded that the missing bolt had failed first, and other bolts fractured in succession in the manner of fatigue fracture. In response, preventive measures regarding inspection strategy have been improved to avoid similar failures.

Dopant-Free Tetrakis-Triphenylamine Hole Transporting Material for Efficient Tin-Based Perovskite Solar Cells.

Developing dopant-free hole transporting layers (HTLs) is critical in achieving high-performance and robust state-of-the-art perovskite photovoltaics, especially for the air-sensitive tin-based perovskite systems. The commonly used HTLs require hygroscopic dopants and additives for optimal performance, which adds extra cost to manufacturing and limits long-term device stability. Here we demonstrate the use of a novel tetrakis-triphenylamine (TPE) small molecule prepared by a facile synthetic route as a superior dopant-free HTL for lead-free tin-based perovskite solar cells. The best-performing tin iodide perovskite cells employing the novel mixed-cation ethylenediammonium/formamidinium with the dopant-free TPE HTL achieve a power conversion efficiency as high as 7.23%, ascribed to the HTL's suitable band alignment and excellent hole extraction/collection properties. This efficiency is one of the highest reported so far for tin halide perovskite systems, highlighting potential application of TPE HTL material in low-cost high-performance tin-based perovskite solar cells.

Investigation of the energy spectra and the electron–hole alignment of the InAs/GaAs quantum dots with an ultrathin cap layer

Abstract The effects of indium composition and the thickness of the combined InGaAs/GaAs thin cap layer on the energy spectra and relative electron–hole alignment of InAs quantum dots (QDs) grown by metal organic vapor phase epitaxy (MOVPE) are investigated by photoelectrical spectroscopy in a semiconductor/electrolyte system. In structures with InAs QDs and an InGaAs strain reducing layer, the shift of the hole׳s wave function to the QDs׳ top was revealed, which indicates In enrichment of the area near the top of QD׳. In structures with an ultrathin GaAs cap layer a change of the sign of the built-in dipole moment was observed. This is explained by coupling effects of quantum-confined electrons with surface states.

Charge-Transport Anisotropy in a Uniaxially Aligned Diketopyrrolopyrrole-Based Copolymer.

Aligned films of a semiconducting DPP-based copolymer exhibit highly anisotropic charge transport with a band-like temperature dependence along the alignment direction and hole mobilities of up to 6.7 cm(2) V(-1) s(-1) . X-ray diffraction measurements reveal an exceptional degree of in-plane alignment, high crystallinity, and a dominant face-on orientation of the polymer backbones. The surprising charge-transport properties are interpreted in a tie-chain model consistent with anisotropic activation energies.

Improved electrospray design for aerosol generation and flame propagation analysis

Although the hazards of aerosol fires and explosions have been studied for decades the data for aerosol flame propagation is still scarce. Additionally there is a lack of standard techniques and measurement apparatus, which impedes the development of optimal aerosol hazard mitigation measures. The focus of this study is development of an improved aerosol electrospray device for the generation of high quality aerosol data. The goal is achieved through higher nozzle packing, precise nozzle and mesh hole alignment and adding two ground meshes. In addition to a flat ground mesh, the utilization of a cylindrical ground mesh demonstrated improved confinement and guidance of droplets. Duratherm 600, heat transfer fluid, was examined to demonstrate the modified electrospray device capabilities as compared to previous design. Results show the modified electrospray can produce more uniform droplets, more even test chamber dispersion, smaller droplet size and higher concentration aerosol, which is essential to study aerosol flame propagation. Accordingly, the results of aerosol flame speed tests for the improved design were more reproducible. Moreover, it was found that a traditional propane pilot flame was unable to ignite the smaller aerosol droplet size due to the strong turbulence generated by the open flame. However, by careful modification of the pilot flame length, the turbulence decreased dramatically and the small droplet size aerosol can be tested.

Visual Servoing of Automatic Alignment System Using Model Predictive Control

Over the past few decades, vision based alignment has been accepted as an important technique to achieve higher economic benefits for precision manufacturing and measurement applications. Also referred to as visual servoing, this technique basically applies the vision feedback information and drives the moving parts to the desired target location using some appropriate control laws. Although recently rapid development of advanced image processing algorithms and hardware have made this alignment process an easier task, some fundamental issues including inevitable system constraints and singularities, still remain as a challenging research topic for further investigation. This paper aims to develop a visual servoing method for automatic alignment system using model predictive control (MPC). The reason for using this optimal control for visual servoing design is because of its capability of handling constraints such as motor and image constraints in precision alignment systems. In particular, a microassembly system for peg and hole alignment application is adopted to illustrate the design process. The goal is to perform visual tracking of two image feature points based on a XYθ motor-stage system. From the viewpoint of MPC, this is an optimization problem that minimizes feature errors under given constraints. Therefore, a dynamic model consisting of camera parameters and motion stage dynamics is first derived to build the prediction model and set up the cost function. At each sample step the control command is obtained by solving a quadratic programming optimization problem. Finally, simulation results with comparison to a conventional image based visual servoing method demonstrate the effectiveness and potential use of this method.

Controlling the 2phole alignment in neon via the 2s-3pFano resonance

We study the state-resolved production of neon ion after resonant photoionization of Ne via the $2s$-$3p$ Fano resonance. We find that by tuning the photon energy across the Fano resonance a surprisingly high control over the alignment of the final $2p$ hole along the polarization direction can be achieved. In this way hole alignments can be created that are otherwise very hard to achieve. The mechanism responsible for this hole alignment is the destructive interference of the direct and indirect (via the autoionizing $2s^{-1}3p$ state) ionization pathways of $2p$. By changing the photon energy the strength of the interference varies and $2p$-hole alignments with ratios up to 19:1 between $2p_0$ and $2p_{\pm 1}$ holes can be created: an effect normally only encountered in tunnel ionization using strong-field IR pulses. Including spin-orbit interaction does not change the qualitative feature and leads only to a reduction in the alignment by $2/3$. Our study is based on a time-dependent configuration-interaction singles (TDCIS) approach which solves the multichannel time-dependent Schr\"odinger equation.

Non‐inverted electron–hole alignment in InAs/InP self‐assembled quantum dots

AbstractPhotoluminescence from individual InAs/InP quantum dots embedded within a planar n–i structure is studied as a function of vertical electric field. We demonstrate control of the electron number and determine the Stark shift and built‐in dipole at zero electric field. In contrast to the well studied InAs/GaAs quantum dot material system, we obtain a built‐in dipole which indicates that the electron lies above the hole at zero electric field. The magnitude and direction of the measured dipole suggests a uniform quantum dot composition. The gating principles we demonstrate can be applied to pre‐positioned InAs/InP quantum dots, such that arrays of initialized single spins can be employed for quantum information applications. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Micropeg and Hole Alignment Using Image Moments Based Visual Servoing Method

The conventional image-based visual servoing leads to image singularities that might cause control instabilities. To avoid this problem, in this paper, the image moments are used as features for visual servoing, where the Jacobian matrix is full rank and upper triangular. Thus, it has the maximal decoupled structure and simplifies the controller. The general analytical form of the interaction matrix or the Jacobian matrix considering the camera parameters related to any image moments is derived in this paper. As a servoing controller, an optimal visual PD controller is presented to improve the performance of the visual servoing system instead of the P controller, which is the method extensively used in visual servoing. A genetic algorithm-based PD parameters tuning method is applied to obtain the optimal parameters. The method proposed is used to align the micropeg and hole, and the simulation results show that the object can reach its desired position faster and more smoothly.