Armor Layer Research Articles

Procedure of Numerical Modelling and Estimation of Sieve Curve Changes as a Tool to Define Riverbed’s Erodibility

The numerical 1-D HEC-RAS modelling tool was supported by the estimation of the sieve curve changes procedure to measure the scale of predicted discharges along a stretch of stream in southern Poland on the Olkusz Upland. The procedure was calibrated in southern Poland on the mountain streams during high-stage events, using a radiotracer application in bedload transport. Particular terrain hypsometry, created by the dissolution of limestone, forced the deep erosion of the river valley bottom; it is here that the current shape of the riverbed of the Prądnik stream is placed. While numerical modelling is widely used in hydraulics, standards have been set for the estimation of flood risk zones; these estimations suggest that the densities of the measured cross-sections are less then optimal, and that the erosive processes are more frequent. This was proved by identifying a number of erosive sections. A new procedure proposed combining the prediction of grain size distribution with hydraulic modelling. Calculations using the estimation of sieve curves, based on the processes of creation and destruction in the armouring layer, have proven to be a challenge for the existing standards of hydraulic modelling. We believe that it is easy to expand the usefulness of the 1D model by utilising its results for this procedure. For the purpose of this type of analysis, dense cross-section measurements are involved, careful modelling is required and a wide range of additional in-field data has to be gathered. For the interpretation of the results, the relation between channel-forming discharge, bankfull discharge, present and critical shear stresses, as well as the mean diameter of the grain size and other estimated sieve curve parameters, were evaluated. Channel-forming discharge is smaller than the bankfull discharge in more than one third of the segment where the erosion process is more frequent and the stability of the riverbed is compromised. Channel-forming discharge was at least twice as high in the stable sections, compared to the erosive section. The presented method will help to find unstable riverbed sections, in order to mitigate the dimension of river training techniques and protect the natural state of the river. While we are in the period of development in this region of Europe, limiting the scope of interference in rivers and streams by applying this method may create an opportunity for the concept of river training close to nature.

Surface roughness measurement for the assessment of damage dynamics of existing and upgraded cube-armored breakwaters

Behavior of existing or upgraded rubble-mound breakwaters with non-conventional geometry, layering and surface porosity may be quite different from what predicted by state-of-art design approaches, and traditional techniques for damage estimation may be not sufficient. In the present work, a novel SfM-based technique for the analysis of damage mechanisms of cube-armored breakwaters is proposed, which is based on the evaluation of descriptors of the macro and micro-roughness of the armor layer. The first one represents the waviness of the armor slope, whereas the latter one is a proxy of the armor layer surface porosity. A systematic experimental investigation was performed, considering different upgrading options for a harbor rubble-mound breakwater with cube-shaped armor units, which involve, besides the rise of the wave wall, the addition of extra armor blocks similar or smaller than the existing ones. Damage measurements acquired through traditional laboratory techniques were combined with the armor surface roughness descriptors. The results of the novel analysis of the cube armor layer macro-roughness revealed that the processes which cause the displacement of the outer blocks are influenced by the level of waviness of the armor slope. Moreover, the quantitative analysis of the micro-roughness enabled the automated identification of four damage mechanisms experienced by the outer armor layer: (i) static equilibrium; (ii) incipient instability; (iii) bulk displacement; (iv) individual displacements. The use of the proposed roughness parameters makes simple and immediate the quantitative comparison between the performances of different upgrading solutions. • A novel SfM-based damage analysis technique for cube-armored breakwaters is proposed. • The armor layer surface is described through non-dimensional roughness descriptors. • Experimental data on upgraded structures are compared to the predictions of state-of-art. • The armor slope waviness significantly influences the stability of the upper layers. • Four damage mechanisms are identified as a function of a new roughness parameter.

Damage Evolution Prediction during 2D Scale-Model Tests of a Rubble-Mound Breakwater: A Case Study of Ericeira’s Breakwater

Melby presents a formula to predict damage evolution in rubble-mound breakwaters whose armour layer is made of rock, based on the erosion measured in scale-model tests and the characteristics of the incident sea waves in such tests. However, this formula is only valid for armour layers made of rock and for the range of tested sea states. The present work aims to show how the Melby methodology can be used to establish a similar formula for the armour layer damage evolution in a rubble-mound breakwater where tetrapods are employed. For that, a long-duration test series is conducted with a 1:50 scale model of the quay section of the Ericeira Harbour breakwater. The eroded volume of the armour layer was measured using a Kinect position sensor. The damage parameter values measured in the experiments are lower than those predicted by the formulation for rock armour layers. New ap and b coefficients for the Melby formula for the tested armour layer were established based on the minimum root mean square error between the measured and the predicted damage. This work shows also that it is possible to assess the damage evolution in scale-model tests with rubble-mound breakwaters by computing the eroded volume and subsequently, the dimensionless damage parameter based on the equivalent removed armour units.

Application of SWASH to Compute Wave Overtopping in Ericeira Harbour for Operational Purposes

This work aimed at testing the capability of the numerical model SWASH to be implemented in the prototype of the overtopping and flooding forecast system HIDRALERTA for Ericeira harbour. In contrast to the neural network NN_OVERTOPPING2, which is currently implemented in HIDRALERTA, SWASH is able to estimate the flood extension and wave propagation along the domain, which makes it a possible improvement to NN_OVERTOPPING2. The one-dimensional version of the SWASH model was implemented to simulate overtopping at two different profiles (antifer and tetrapods) and calibrated for three storms in 2019 by comparing the simulated overtopping discharge to NN_OVERTOPPING2 results. For the calibration, the Manning coefficient was used to represent the friction of the armour layer. Then, for operational purposes, four expressions to calculate the Manning coefficient were developed based on: the relative crest freeboard, the wave steepness, the incident wave angle and the type of armour layer. The expressions showed small errors between the calculated and calibrated Manning coefficients and highlighted the importance of the incident wave angle to obtain an accurate calibration. Despite an underestimation of the overtopping discharge in some cases, the SWASH model was found to provide overall good results when applied with calculated Manning coefficients and suitable to be implemented in HIDRALERTA.

Tensile failure behavior of unbonded flexible riser with damaged tensile armor wires

Unbonded flexible risers (UFRs) connect surface production platforms to subsea production systems, and are therefore vital for tasks such as the transportation of oil and gas and the injection of water. The tensile armor layer is the main load layer of UFRs. Once this layer is partially broken, the safety of offshore oil and gas gathering and transportation is seriously threatened. In this study, an 8-layer UFR model is developed to calculate the effects of damaged inner and outer armor wires and boundary conditions on the tensile stiffness, ultimate load capacity, and stress distribution and load ratio of the inner and outer tensile armor layers. Broken inner tensile armor wires are found to have a greater impact on the tensile properties and produce the same torsional buckling failure mode as observed in the field. The influence of the pressure load on the ultimate load capacity of the UFRs is analyzed, and the results demonstrate that the outermost pressure increases the interlayer action between the tensile armor layers and the adjacent layers, thereby reducing the torsional angle of the UFRs under the ultimate tension. Additionally, the innermost pressure is found to have a negligible effect on the ultimate load.

Mechanism exploration and effective analysis method of shear effect of helically wound structures

Helically wound structures are widely used in practical engineering due to its excellent mechanical property, such as the steel rope, the reinforced armor layer of the marine flexible pipe/cables. The shear stiffness plays an important role in exactly predicting the mechanical response of the helically wound structure, especially for the short structure. There has been no general methodology to directly calculate the shear effect of this type of structure because of the geometrical complexity. This paper introduces and modifies a novel implementation of asymptotic homogenization method so-called NIAH to effectively calculate the shear property of the helically wound structure. This modification of NIAH is derived based on the strain energy equivalence of the macroscopic structure and the microscopic structure so-called the microscopic unit cell, which can be used to quickly calculate the effective stiffness and effective stress. In this paper, the effective stiffness is only discussed. The mechanical mechanism of the shear effect of helically wound structures is firstly explained, and then taking into account the shear effect, a quickly effective analysis method of the mechanical response for the helically wound structure is proposed. The efficient and accurate finite-element model of the unit cell which is used in the numeric implementation of the effective analysis method, is determined through the sensitivity analysis of meshing methods and periodic boundary conditions. Considering the practical application, the implementation of this method is validated for helically wound structures with equal-scale subcomponents and non-equal-scale subcomponents. The influence of the slenderness ratio on the shear effect is also explored in this work. This study provides a meaningful reference for the loading analysis and structural design of helically wound structures. • A method for calculating shear property of helically wound structure is proposed. • Mechanical mechanism of shear effect of helically wound structure is revealed. • The influence of the slenderness ratio of structure on shear effect is studied. • An accurate and efficient model of unit cell is determined by sensitivity analysis. • Shear property of equal-scale and non-equal-scale structures is discussed.

Channel Evolution Triggered by Large Flash Flood at an Earthquake-Affected Catchment

Earthquakes–induced landslides generally provide abundant loose materials at hillslopes, possibly triggering morphological reshaping processes at river channels and riverbeds during the large flash flood hydrograph and bringing huge risk downstream. Therefore, in a Wenchuan earthquake-affected catchment, the collected hydro-meteorological data and high-precision small Unmanned Aerial Vehicle (sUAV) data were used to quantitatively analyze channel evolution by a large flash flood event on 25 and 26 June 2018. It was found that the stable riverbed structure formed by the armour layer appeared in the tenth year after the Wenchuan earthquake. In a confined channel, the layer can protect the channel and resist the drastic change after the flash flood event with only a small bed elevation from 0.2 m to 2 m. Without the protection of the armour, the change could reach 6 m in the unconfined channel. Meanwhile, more materials with a deposition volume of about 7450 m3 from tributaries were generally taken to the main channel, and more intense erosion with a volume of 105 m3 mostly occurred downstream of tributaries. It was noted that, in the cross-section, the increased channel width could lead to a significant change with the large volume of 35 m3. Additionally, a conceptual diagram of the generalized channel response to large flash floods was provided during multi-stage periods after the Wenchuan earthquake. It determined the rebalance processes of channel evolution in the tenth year after the earthquake. This study will contribute to understanding the post-earthquake long-term channel evolutions and could provide decision-makers of assessing the mitigation strategies for higher-magnitude flood disasters triggered by channel change in earthquake-affected watersheds.

Influence of structural parameters of unbonded flexible pipes on bending performance

Unbonded flexible pipes have complex structural forms and numerous structural parameters. There are different degrees of contact and slip between the structural layers under bending loads, which brings challenges to the structural design and bending characteristics analysis of flexible pipes. In this paper, according to the law of energy conservation and deformation geometry theory, the mechanical equilibrium equation of each layer of unbonded flexible riser under bending load is established and the contact condition between layers is introduced in the first step. According to the slip state of the spiral strip, the response of the flexible riser under bending load was divided into three stages: no slip, partial slip and complete slip. The expressions of bending moment and bending stiffness were derived. The influence of structural parameters of tensile armor layer of unbonded flexible pipes on its bending performance under bending load is studied by using MATLAB software to compile the corresponding calculation program. The results show that the increase of friction coefficient between layers of tensile armor will improve the bending resistance of flexible pipes. The increase of helix angle will reduce the bending stiffness of flexible pipes in the initial stage. The increase of the number of spiral strips will increase the bending stiffness of flexible pipes in the initial stage. In the process of structural design of flexible pipes, the influence of the above structural parameters on the bending characteristics of flexible pipes should be taken into account.

Experimental characterisation and numerical simulation of ballistic penetration of columnar ceramic/fiber laminate composite armor

To improve the design of lightweight, high-performance bulletproof armors, three columnar ceramic/fiber laminate composite armors were designed and prepared, and their ballistic behavior against 7.62 mm armor-piercing bullets was investigated. Through the microcomputed tomography (micro-CT) analysis of target samples, B4C ceramics were found to exhibit better comprehensive bulletproof properties than SiC ceramics, with a 142 % improvement in the protection margin. The design realized by combining ultra-high-molecular-weight polyethylene (UHMWPE) with aramid III could help decrease the backface signature (BFS) by 53 %. A numerical simulation model was established by combining the smoothed particle hydrodynamics (SPH) and finite element (FE) method, called the SPH–FE method, considering the strain rate effect. The SPH–FE model could accurately describe the damage morphology and contribution of the ceramics in terms of the energy dissipation. The damage radius of the ceramic layer was effectively constrained by the design of the columnar ceramic. The maximum error of the SPH–FE model was 6.41 %. The damage mechanism of each layer of the composite armor in the penetration process was explored in detail. A transition from shear damage to tensile damage occurred with layering as the transition marker.

How does the selection of wave hindcast datasets and statistical models influence the probabilistic design of offshore scour protections?

Offshore wind structures often use bottom-fixed foundations that are susceptible to scour phenomena. The design of scour protections for such structures requires defining the physical actions that they must be able to withstand during their lifetime. In this context, hindcasts providing estimates of necessary metocean variables play a key role. However, it is unclear how the selection of hindcast datasets can influence the design of scour protections at a given location. Moreover, defining design actions requires estimating extreme sea states with return periods exceeding the length of hindcast time series, which introduces additional uncertainty in the modelling process, as different statistical models may perform differently when applied to different hindcast datasets. A better understanding of the effects of these modelling choices is therefore necessary for the design and optimization of scour protections. The present study compares different wave hindcasts for the North Sea, and analyses how their selection and the subsequent application of statistical models affect the estimated probabilities of failure of the armour layer for bottom-fixed monopile foundations. Results show that the selection of different hindcast datasets and statistical models can significantly influence the probabilistic-based design of this type of scour protection, based on which practical recommendations are provided.

The limits to growth: how large can subaqueous, flow-transverse bedforms ultimately become?

Based on field and experimental evidence, the average initial spacing (seed wavelength) of flow-transverse bedforms (ripples and dunes) appears to lie between 80 and 130 grain diameters (L = 80–130Dmm). Starting with an average initial spacing of L = 100Dmm, subsequent bedform growth proceeds by amalgamation of two successive bedforms, which results in a doubling of the spacing in each step. Geometric principles dictate that the combined volume of two smaller bedforms lacks about 40% of the volume required for a fully developed amalgamated bedform. The missing volume is gained by excavation of the troughs, i.e., by lowering the base level. Where base level lowering is prevented by the presence of a coarse-grained armor layer or hard ground pavement, the larger amalgamated bedform remains sediment starved. In its simplest form, bedform growth proceeds by continuous doubling of the spacing in response to increases in flow velocity, the process being reversible in response to flow decelerations. Bedform growth terminates when the shear velocity (u*) at the crest reaches the mean settling velocity (ws) of the sediment. At this point, 40% of the bed material is in suspension, at which point the missing volume can no longer be compensated by trough excavation. In shallow water, maximum bedform size is dictated by the water depth, whereas in deep water, bedforms can potentially grow to their ultimate size. Evaluation of bedform data from deep water settings suggests that the largest two-dimensional, flow-transverse bedforms in terms of grain size (phi) can be approximated by the equations: lnLmax = 13.72–4.03Dphi and lnHmax = 9.95–3.47Dphi for grain sizes < ~ 0.2 mm (> ~ 2.32 phi), with L and H representing bedform spacing and height in meters and D the grain size in phi. For grain sizes > ~ 0.2 mm (< ~ 3.23 phi), the corresponding relationships are lnLmax = 6.215–0.69 Dphi and lnHmax = 3.18–0.56Dphi, with notations as before, or in terms of grain diameters in mm: Lmax = 5 × 105Dmm.

Effect of sediment gradation on scour by symmetric crossing jets: an experimental investigation

Abstract A laboratory study with 162 experiments was designed and conducted to investigate the effect of three non-uniform sediment samples on the scour morphology by the symmetric crossing jets. The bed sediment materials with close median diameter values and different non-uniformities were utilized to investigate the scour at various crossing angles. The results were also compared with the equivalent single jet. The proper novel relationships were presented to predict the scour hole depth, and dimensions. The results showed that at a crossing angle of 30° with low and medium tailwater depth, the scour depth increases with increasing the non-uniformity of the bed materials. At the crossing angle of 30°, the armor layer was created perfectly that was thick on the bottom of the scour hole, but for the crossing angles of 70° and 110° it was thin and was a mixture of the coarse and fine particles. At low tailwater depth at the crossing angles of 70° and 110°, by increasing the non-uniformity of the sediments, the scour tended to be more asymmetric. At the high tailwater depth, for the crossing angles of 70° and 110° the scouring was less than that of the crossing angle of 30° and single jet.

Electrodeposition of Functionally Graded Brazing Interlayers for Enhanced Joint Strength between Fusion Plasma-Facing Materials and Heat Sinks

In response to the significant plasma science and engineering breakthroughs witnessed over the past decade, the fusion research community has developed an ambitious roadmap to achieve large-scale, energy-positive fusion reactors that will enable economically competitive fusion electricity. Critical to the success of commercial fusion energy is the development of materials able to serve as plasma facing components (PFCs) that can withstand the unprecedented high heat, particle, and neutron fluxes within the fusion reactor. Tungsten is a leading candidate for the plasma-facing portion of these PFCs because of its high melting point, high sputtering resistance, and low tritium retention. Copper or copper-based alloys (e.g., copper-chromium-zirconium alloy C18150) and reduced activation ferritic/martensitic (RAFM) steels have been proposed for the heat sink materials behind the tungsten armor due to their high thermal conductivity. Brazing is considered a promising method for joining the tungsten armor and heat sink layer. However, the extreme mismatch in the coefficient of thermal expansion (CTE) between tungsten and these potential heat sink materials makes directly joining these two layers challenging. This thermal stress can be reduced by incorporating a joining layer of functionally graded materials between the tungsten and heat sink that imparts gradual changes in CTE. Copper/tungsten or copper/tungsten carbide composites are leading candidates for these functionally graded materials. For these composites, gradual changes in the CTE are achieved by varying the volume fraction of tungsten/tungsten carbide in the composite, from tungsten-rich at the tungsten armor to tungsten-poor at the heat sink.This talk will discuss the development of a scalable, electrochemical approach for fabricating interlayers with functionally graded CTE that can decrease the thermal mismatch between tungsten PFCs and copper or RAFM-based heat sinks. In this approach, the copper/tungsten or copper/tungsten carbide composite are electrodeposited onto the tungsten PFC. This component is then bonded to the heat sink via brazing. A key objective of the work is to achieve compositional control during electrodeposition through the use of highly tunable pulse and pulse-reverse electric fields. Engineering of the electric field enables control of the mass transport and crystallization phenomena in the deposition process and thus enables control of composite properties such as composition, porosity, and surface roughness. Results from electrodeposition trials and mechanical testing of brazed joints under ambient conditions as an initial screen for interlayer performance will be discussed, in anticipation of high-heat flux testing of joint performance under fusion-relevant conditions.

Impact of damaged external polymeric layer on axial compressive response of flexible pipes

A fully three-dimensional finite element model was developed in order to study the axial compressive response of flexible pipes. The model is parameterized and features five layers, with emphasis on the layers responsible for reacting to axial loads. Tensile armor instability may occur in the form of lateral buckling and radial buckling, also known as “birdcaging”, which is influenced by several parameters, including defects on the layers that are supposed to restrain and protect the tensile armor, more specifically, the external polymeric layer. By being the outermost layer, the external sheath is responsible for keeping the pipe watertight and it is the most likely to sustain damage from launching, collision from vessels, anchors or ice structures and even damage caused by sea creatures. This article focuses on the effect of damage on the external polymeric layer on the tensile armor instability failure modes and uses a finite element model to simulate that phenomenon. For that purpose, the outermost layer was deliberately damaged with cuts on a key position. The cut dimension is parameterized for this analysis and the results will show that, if the flexible pipe is equipped with a high strength layer and the differential pressure is not taken into account, the external polymeric layer will not play an effective part on protecting the tensile armor layers from instability. However, it may influence the triggering of the instability on a specific position of the pipe.

Friction coefficient influence in a flexible pipe: A macroelement model

Flexible pipes are structures responsible for several operations in offshore playing a vital role and hold immense importance in oil extraction.Modelling such pipes is not trivial, due to its layered structure. The helical wounded wires layers, which are responsible for handling axial loads, present a challenge in modelling in special. Another important factor for consideration are layer interactions, since they play a major role in pipe behavior.To obtain the pipe response under various loads, the authors proposed the macroelement model: a finite element model in which elements take profit of the problem geometrical characteristics, simplifying the meshing process and contact treatment, while reducing memory use and processing time.The present article is an excerpt of this research line and focuses on the understating of the frictional behavior in layer interactions by studying a flexible pipe. The model considers all the previous developed elements to simulate a four-layered flexible pipe, consisting of two tensile armor layers and two cylindrical ones. The loading considered is pressure combined with either tension or compression and the effects of the friction coefficient are investigated. Resultsare compared to classical finite element for validation, showing excellent agreement, differences in performance and efficiency are highlighted.

A Composite Permeable Sloping Seawall for Effective Energy Dissipation: A Quasi-Soft Alternative Solution for Shore Protection

The recent trend in coastal research centers around environmental sustainability, especially in coastal conservation. A seawall typically has three layers, namely core, filter, and hard rubble/concrete armor. In the current study, a two-layered seawall is proposed, comprising a coir geotextile roll from the coastal regions, along with sand encapsulated in a geotextile over an impermeable core. This can be considered as a quasi-soft solution against the traditional, three-layered, hard alternative. The objective of this study is to investigate the combined effect of slope and porosity, of this composite structure, on the wave reflection. The findings show that the composite structure provides less reflection coefficient values compared to traditional rubble mound seawalls. Four orientations and positions of coir rolls with geosynthetic sandbag were tested. The armor layer with coir rolls overlain by geosynthetic sandbags over an impermeable core could be a better alternative, as it increases the hydrodynamic performance by 59% as compared to sandbags, used alone, over an impermeable core on a slope of 1:2.

On the pressure–torsion response of a flexible pipe with section ovalization

Ovalization, as an important factor affecting the performance of flexible pipes, is unavoidable in the manufacturing process. In this paper, a model of a flexible pipe with initial ovalization is established numerically. The numerical model is verified by a case analysis, and the influence of ovalization on the torsional response of a flexible pipe is discussed. It is found that the ovalization always has a negative effect on the torsional stiffness of the flexible pipe. Then, the effective numerical model is used to calculate the torsional response of a flexible pipe with initial ovalization under dry and wet annulus pressure. It is found that the dry annulus pressure improves the torsional stiffness of the flexible pipe by advancing the interaction between the layers and hindering the radial expansion of the outer tensile armor layer. However, the dry annulus pressure also increases the stress of the tensile armor layers, which reduces the withstanding capacity of the flexible pipe. Especially with the increase of ovalization, the loading capacity decreases more obviously. The wet annulus pressure has little effect on the torsional response of the flexible pipe, but it extends the risk of radial collapse of the carcass layer.

Sustainable colorimetric/luminescent sensors enabled by armored lipid nanoparticles

In this study, we developed a highly stable polymeric vesicle using a nanosilica-armor membrane to achieve a sustainable colorimetric/luminescent response. The silica armor can be grown directly as ~ 5 nm spherical nanoparticles on the surface of the diacetylene (DA) vesicle with liposomal structure. This can be accomplished via the modified Stöber reaction in pure water on a layer of amine linkers deposited on the vesicles. Once formed, the structural stability of the DA vesicles dramatically increased and remained so even in a dried powder form that could be stored for a period of approximately 6 months. Then, redispersed in water, the armored vesicles did not agglomerate because of the electric charge of the silica armor. After polymerization, the polydiacetylene (PDA) vesicles maintained an average of 87.4% their sensing capabilities compared to unstored vesicles. Furthermore, the silica membrane thickness can be controlled by reiteration of the electrostatic layer-by-layer approach and the direct hydrolysis of silica. As the number of silica armor membranes increases, the passage of the stimuli passing through the membranes becomes longer. Consequently, three layers of silica armor gave the PDA vesicles size-selective recognition to filter out external stimuli. These discoveries are expected to have large-scale effects in the chemo- and biosensor fields by applying protective layers to organic nanomaterials.Graphical

Corrosion of tensile wires covered with PA11 layers in simulated annulus environments at low CO2 pressure

AbstractHigh‐strength carbon steel wires covered with polymer layers were exposed to different test environments simulating the conditions in the annulus of flexible pipes at low CO2 pressure and flooded with seawater. The polymer layers mimicked the antiwear tapes which are placed in between the steel layers of the tensile armor of the pipes. Specimens without the polymer layer were exposed to the same test environments for comparison and allowed identifying how the presence of the polymer layer influenced the corrosion mechanism. In some of the experiments, oxygen was introduced into the gas mixture to simulate fresh seawater entering the annulus after a breach in the outer sheath. Surface analysis of the corroded specimens after removal of corrosion scales was carried out by scanning electron microscopy, optical profilometry, and confocal microscopy. The polymer layers were observed to have a considerable effect on the corrosion morphology.

Double-side modification strategy for efficient carbon-based, all-inorganic CsPbIBr2 perovskite solar cells with high photovoltage

CsPbIBr2 has attracted great attention due to its balanced bandgap and stability features. However, one-step prepared CsPbIBr2 films are generally of poor quality, hindering the performance improvement of the resulting perovskite solar cells (PSCs). Herein, we report the fabrication of high-performance carbon-based, all-inorganic CsPbIBr2 PSCs with a double-side modification strategy using PEAI/PEABr. We tune the crystallization behavior and passivate the defects of CsPbIBr2 films with modifications of their bottom and top surfaces with PEAI and PEABr, respectively. This causes the PEA cation to form a double layer of armor on both sides of the CsPbIBr2 precursor film and can provide the anions of the required I and Br. The collaborative strategy of crystallization and defect passivation for CsPbIBr2 films is exceptionally effective. It produces a fully covered CsPbIBr2 film with an average grain size increase of more than 50%, few grain boundaries, and high crystallinity. Moreover, this strategy also suppresses pinhole formation, reduces the charge trap density, and prolongs the carrier recombination lifetime. Hence, carbon-based all-inorganic PSCs with the desired CsPbIBr2 films yield an optimized efficiency of 9.96% with a particularly high photovoltage of 1.32 V. Our work provides guidance for simultaneous crystallization control and defect passivation to further improve the performance of PSCs.