Active systems, such as contraction of muscle fibers and action potential propagation in neural networks, exhibit efficient directional transport of information and energy. Bringing these biological principles into engineered systems can overcome the limitations of passive metamaterials in tunability after fabrication, spontaneous reset, and the realization of dynamical nonreciprocity. However, a unified and transparent analytical framework for reversible nonreciprocal wave propagation governed by coupled fast-slow dynamics remains absent. We develop a mechanical lattice composed of active bistable elements incorporating a displacement-driven slow recovery variable to emulate biologically inspired recovery processes and capture the evolution of active stiffness. Discrete and continuum models are derived to describe the lattice dynamics. Building on continuum descriptions, we employ singular perturbation and matched asymptotic expansions, complemented by machine learning, to enable analytical characterization. Then we define a metric of nonreciprocal energy transport and map the key parameters to quantify how system parameters jointly control wave speed and propagation direction. Nonlinear results reveal that forward and backward transition waves propagate at markedly different steady speeds, demonstrating pronounced nonreciprocity. The key mechanism arises from the coupling between fast excitation and slow recovery, which produces a refractory effect that resets the energy landscape and therefore breaks time reversal symmetry in a geometrically symmetric structure. During the evolution of active stiffness, an intermediate phase emerges and co-propagates with the mechanical wave and selectively suppresses returning waves under appropriate timing conditions. Consequently, reversible and tunable nonreciprocal transition waves are achieved. We obtain bidirectional wave solutions, along with analytical expressions for wave speed, width and energy flux as well as their conditions of validity. Theoretical predictions agree closely with numerical simulations and demonstrate that the nonreciprocity depends on the recovery rate in a nonlinear manner. This study provides a general theoretical framework and practical design guidelines for bioinspired intelligent metamaterials that enable reversible directional energy routing, signal isolation, and mechanical logic, and it also informs the design of field controlled phase change materials and multiphysics devices.

The construction of 2D/3D perovskite bulk heterojunctions can combine the stability of 2D perovskites with the favorable charge carrier transport properties of 3D perovskites, thereby enabling efficient and durable perovskite solar cells. However, the controlled manipulation of the n-value and phase purity of the 2D perovskite within the heterojunction often faces significant challenges due to the complex quantum well structure and the chemical environment of the reaction. In this study, we obtained bulk heterojunction films comprising n = 3 BA2MA2Pb3I10 2D perovskite and 3D perovskite by adding BA2MAPb2I7 2D perovskite single crystal precursors into a 3D perovskite precursor solution. The introduction of the 2D perovskite enhances the built-in electric field of the perovskite solar cell and passivates film defects, thereby reducing non-radiative recombination and promoting charge carrier transport and collection, leading to significant improvements in VOC, FF, and PCE. Furthermore, both the 2D/3D perovskite films and the corresponding solar cells exhibit substantially improved stability.

The most efficient perovskite solar cells (PSCs) are currently developed using antisolvent-based fabrication technology. Despite extensive analysis of various aspects of the antisolvent method-such as the type of antisolvent, dropping time, and precursor compatibility-some antisolvents still produce uneven film surface morphology on centimeter-scale substrates. The decoupling of the relationship between local structural characteristics, such as grain boundaries and defects, and the optoelectronic performance of PSCs is currently one of the most highly regarded research issues in the field. In this study, we utilized high-resolution white light interferometry to characterize the morphological distributions of perovskite films from the center to edge, using anisole as an example of the antisolvent. We observed that macro cracks at the center of the film typically exhibit dense ridge morphology, while cracks toward the edges display a concave morphology. We analyze the stress mechanism by using EDS mapping and AFM in detail, attributing this phenomenon to the competitive attachment of 2D islands and boundaries for adatoms, which are influenced by changes in grain size. The devices at different locations were fabricated and their performance analyzed. Our findings indicate that these protruding cracks do not significantly affect the current and voltage of the photovoltaic device; however, concave cracks lead to a decrease in the device fill factor. We attribute this decrease to enhanced carrier recombination at the interface due to this morphology. This study provides valuable insights into the formation of perovskite film morphology under antisolvent treatment and the relationship between film local morphology and PSCs performance.

As a classical low-cost technique, dip coating has not been used for printable electronics. Here, the study demonstrates large-area organic solar cells can be made by dip coating. The correlation is revealed among Van der Waals forces in precursor film, aggregation state of polymer, and fibrous orientation in active layer; the relationship is also expounded between fluid mechanics of the confined liquid in polymer scaffold and the continuity of the acceptor phase. By controlling the fluid characteristics, the ideal nanoscale bicontinuous interpenetrating network forms. As a result, the 1.0 cm2 rigid and 10.0 cm2 flexible cells exhibit efficiencies of 17.9% and 13.7%, respectively. Moreover, the method for predicting the optimal coating speed for the dip coating of given inks is proposed. Overall, this work not only demonstrates the superiority of dip coating for organic solar cell fabrication but also provides guidance for its application in printable electronics.

Scalable fabrication of perovskite films with homogeneous structure remains a critical challenge in bridging power conversion efficiency gap between solar modules and laboratory-scale cells. To address this, we propose a slot-die coating strategy with pyrrodiazole additives in the perovskite precursor solution to simultaneously immobilize lead iodide and formamidinium iodide. This approach enhances wet film stability by suppressing colloidal aggregation, retards the crystal growth process, and ensures a consistent growth rate across the films. These effects promote the formation of large, monolithic grains, enabling large-area perovskite films with homogeneous structure, excellent uniformity, and low defect density under ambient conditions. Using this strategy, we achieved 10 cm × 10 cm inverted perovskite solar modules with a certified efficiency of 20.3%, along with good working stability and excellent application demonstration, showcasing its great potential for industrialization. Yuan et al. report pyrrodiazole additives for simultaneous immobilizing of lead iodide and formamidinium iodide during slot-die coating perovskite films in air, ensuring consistent growth rate for upper and lower layers of the film, leading to certified efficiency of 20.3% for 10 cm × 10 cm solar modules.

The photoacoustic spectroscopy apparatus based on an external cavity quantum cascade laser was employed to simultaneously detect four SF6 decomposition by-products, i.e., SO2F2, SOF2, CF4, and SO2 for the application in diagnostics of the SF6 insulation equipment widely used in high-voltage transmission lines. The influence of background gases SF6 and N-2 with the He addition in different ratios on the SOF2 photoacoustic signal was investigated, with the pure SF6 showing the most pronounced enhancement effect on the photoacoustic signal of the target analyte. The limit of detection of SOF2 in pure SF6 was estimated by comparing the limits of detection of SOF2, CF4, and SO2 in the 95% SF6/5% He combination and pure SF6. The estimated detection limits for SO2F2, SOF2, CF4, and SO2 were 635.4 ppb, 24.0 ppb, 10.3 ppb, and 97.8 ppb, respectively. Finally, the concentration of each decomposition component in the gas mixture of SO2F2, SOF2, CF4, and SO2 in the 95% SF6/5% He background gas was quantified by multiple linear regression.

Kirigami demonstrates distinctive buckling instability behavior when subjected to tensile stress, bestowing the structure with exceptional stretchability and design versatility. Nonetheless, conventional design methodologies predominantly focus on unidirectional cutting kirigami structures, investigating their buckling instability and out-of-plane configurations derived from geometric symmetry. To enhance the functionality of kirigami and thoroughly explore the mechanisms of buckling behavior upon the disruption of geometric symmetry, as well as to comprehend the impact of geometry on programmability during reconfiguration, we have analyzed the buckling instability mechanisms of tessellated cutting kirigami structures. An innovative design strategy for kirigami is proposed, leveraging deep learning techniques to enable accurate predictions of complex nonlinear constitutive relationships. Our approach offers a programmable design framework, facilitating the targeted identification of optimal kirigami structural patterns based on tensile strain requirements, thereby enhancing the adaptability of the desired mechanical response and minimizing trial-and-error costs. Our results indicate a 94.29% accuracy in mechanical performance predictions using the proposed method. The geometric symmetry-breaking considerably broadens the design space for kirigami. Additionally, through cross-selection and functional design of predicted kirigami cells, information encoding and transmission via kirigami metasurfaces can be achieved. This paper presents a forward-looking kirigami design strategy that predicts required mechanical performance based on functional demands and enables functional configuration.

The surface properties of the substrate play a crucial role in regulating the morphology of active layers coated atop and the resulting photoelectronic properties in solution-processed organic photovoltaic (OPV) cells. However, current studies on the relationship between the surface free energy (gamma S) of the substrate and film morphology of the active layers remain superficial. Here, we present an effective method for tuning gamma S by incorporating NiO nanoparticles into commercial PEDOT:PSS hole transport layers (HTLs). Furthermore, we systematically perform the film-forming process and characterize the morphology to quantitatively establish the relationship between surface energy, liquid precursor film length, film-forming kinetics, and morphology. The results indicate that increasing the gamma S of the substrate can elongate the liquid precursor film length, extend the phase separation time, and enhance the crystallinity of the active layer. Consequently, the blade-coated 1.03 cm2 OPV cells based on the PEDOT:PSS:NiO HTL and PBQx-TCl:eC9-2Cl active layer yield a record PCE of 18.70% (certified as 18.51% by the National Institute of Metrology, China); the manufactured 23.60 cm2 OPV modules achieve an outstanding PCE of 16.5%. This work contributes to a deeper understanding of the interface characteristics and morphological control of the blade-coated large-area active layers toward high-efficiency OPV cells. Incorporating NiO nanoparticles into PEDOT controls the surface energy of interface layer, enabling the manipulation of film formation kinetics and morphology of active layer. Consequently, 1.03 cm2 cells achieved 18.5% efficiency.

Kirigami, subjected to escalating strain, frequently exhibits pronounced instability, coupled with remarkable flexibility and extraordinary extensibility. This behavior holds significant relevance for domains associated with malleable and reconfigurable surfaces, including stretchable electronics and modifiable functional devices. Nonetheless, conventional design methodologies, anchored in geometric symmetry and governed by minimum energy principles, tend to manifest buckling instabilities restricted to symmetric and anti-symmetric modes. scrutinize the mechanisms of buckling behavior that disrupt geometric symmetry and comprehend the influence of geometry on programmability during reconfiguration, we propose an innovative strategy for kirigami's design. This strategy capitalizes on advanced deep learning methodologies, employing convolutional neural networks (CNNs) for categorizing buckling modes and recurrent neural networks (RNNs) for prognosticating constitutive relationships. Our approach furnishes a programmable design solution adept at identifying optimal kirigami patterns, characterized by their superior tensile strength and distinct buckling conformations, thereby fulfilling a diverse array of functional necessities. Our results illustrate that the proposed method displays a level of precision in distinguishing between buckling modes of geometric symmetry and patterns that deviate from such symmetry. The buckling mode space has been extended and rediscovered, allowing unique modes to have the potential to be adopted into functional devices. Additionally, it demonstrates minimal losses predicting constitutive relationships. Intriguingly, we discovered that tensile responses are geometry-centric and adjustable. Buckling modes showcase a dependency on geometry, with certain geometric parameters either significantly augmenting the sensitivity of buckling modalities or causing the buckling instability modes to become apathetic and unresponsive. Guided by the principle of target-led pattern parameter design, proffer prospective tactics for the design of kirigami capable of delivering the desired mechanical performance. Moreover, we explore the feasibility of employing alternative biological materials in these designs.

Although significant advancements have been achieved in lead-tin (Pb-Sn) alloyed perovskite solar cells (PSCs), their power conversion efficiency (PCE) remains inferior to that of their Pb-based counterparts, primarily due to higher open-circuit voltage (Voc) losses and lower fill factors (FFs). Herein, we report both perovskite top and bottom interfacial improvements by incorporating a facile fluorophenylethylammonium iodide (p-FPEAI)/ethyl acetate (EA) solution during the film crystal growth. Based on the analysis of perovskite crystallization, film growth, and strain relaxation, the mechanisms behind these interfacial improvements have been well understood. Furthermore, p-FPEAI could reduce the defect density and nonradiative recombination losses, thus attributing to the improved Voc and FF. Finally, the treated device achieved a PCE of 20.14% with a Voc of up to 0.84 V, which is among the highest reported values so far for Pb-Sn alloyed PSCs without additional precursor additives. In addition, the unencapsulated p-FPEAI-treated device maintained its initial efficiency of approximately 92% after being kept in a nitrogen atmosphere for 1 month, in contrast to the control device which retained only 30% of its initial value. Our findings provide a comprehension for understanding the effect of bulky cations as antisolvents on fabricating highly efficient Pb-Sn alloyed perovskite solar cells.

Molybdenum oxide (MoOX) films are typically prepared using a thermally-evaporated MoO3 source (ev.MoO3) as the hole transport layer for inverted organic solar cells (OSCs). However, their low conductivity and interface element diffusion severely limit their efficiency and stability. Herein, a novel and effective thermal evaporation method of the MoO2 source to prepare undoped MoOX films with oxygen-rich vacancies and inhibitory atom diffusion properties electrode using ev.MoO2 as the source, is reported. Electron spin resonance analysis indicates that ev.MoO2 has a stronger oxygen vacancy signal peak than ev.MoO3, which contributes to its excellent conductivity. The inverted organic solar cells modified by ev.MoO2 yielded a significant improvement in short-circuit current density (JSC) and fill factor (FF). The power conversion efficiency (PCE) increased from 16.65% in ev.MoO3 to 17.08% in ev.MoO2 under AM 1.5G, which is one of the highest values ever reported for inverted OSCs. Furthermore, owing to the high transmittance and low trap density, the PCE increased from 20.18% with ev.MoO3 OSC to 22.13% with ev.MoO2 OSC under 500 lux. In addition, scanning transmission electron microscopy and energy-dispersive X-ray spectroscopy confirmed that ev.MoO2 can prevent the diffusion of Al from the electrode to the functional layers, resulting in a T80 exceeding 800h under continuous illumination.

Serpentine interconnects (serpentines) with various degrees of curvature are often designed to absorb deformations and protect brittle active components in flexible devices. Serpentines with small curvature are modelled well using the traditional theory for doing so, but this overestimates the stretchability of serpentines with large curvature (e.g. the relative error exceeds 90%). Proposed here is a novel theoretical model in which a non-buckling serpentine is characterized as a large-curvature beam. Analytical solutions are derived, and systematic experiments and numerical simulations are reported to validate the accuracy and investigate geometrical dependence. It is found that (i) dimensionless geometrical parameters regulate the compliant mechanics of a serpentine, (ii) there is a certain arc angle that produces abnormal stretchability (i.e. the normalized stretchability is less than unity) and (iii) the flexibility and stretchability can be enhanced by between two and five orders of magnitude. This work offers a new way to construct optimal serpentine ribbons with large curvature for various applications.

Soft biological tissues often exhibit notable strain stiffening under increasing stretch, and this can have significant effects on tissue growth and morphological development, such as causing symmetry breaking in growing airways and leading to mucosal folding and airway hyperresponsiveness. To investigate the role of strain stiffening and the multifactorial control in growth and remodeling, we consider a growing tubular structure with strain-stiffening effects caused by increased and tightened collagen. In addition, we employ the nonlinear hyperelastic Gent model and initial stress symmetry theory to include the coupling effects of differential growth and initial residual stress. Results show that for strain stiffening that takes place at higher strain (J(m) > 21), the maximum critical growth ratio matches that obtained using neo-Hookean model calculations. Meanwhile, for biological tissues that exhibit strain stiffening under moderate strain conditions (0.46 < J(m) < 21), the strain-stiffening effect delays significantly the onset of growth instability. When strain stiffening takes place at very low strains (J(m) < 0.46), stiff biological tissues can prevent growth instability, resulting in a smooth hyperelastic cylindrical tubular structure, and the epithelial tissue remains stable at all growth stages without forming any unstable morphology. Our results suggest that strain stiffening can induce retardation instability during biological growth and remodeling, but airway remodeling can incorporate this effect by increasing wall stiffness and reducing obstruction. This highlights the importance of considering the impact of strain stiffening on biological growth and remodeling, which can inform the development of effective clinical interventions for chronic inflammatory airway diseases.

Inorganic tin–lead perovskites with low bandgap (1.2–1.4 eV) are desired absorber materials for solar cells owing to their ideal bandgap and compositional stability. However, such tin–lead perovskites are currently subject to inferior power conversion efficiency (PCE) and the origin remains unclear. Here, for the first time, we report the metal-cation-derived unsynchronized crystallization behavior of inorganic tin–lead perovskite, exemplifying by a representative composition CsPb0.7Sn0.3I3. A tin-perovskite-targeted crystallization modulation agent, 1-(4-fluorophenyl) piperazine (1-4FP), is introduced to synchronize the B-site alloying through its strong targeted bonding with SnI2, resulting in substantially enhanced film quality with better morphology and photoelectrical properties. Furthermore, first-principles molecular dynamics simulations reveal that the agent regulates the crystallization route toward the pure phase of CsPb0.7Sn0.3I3 by suppressing the preforming of tin perovskite. With our proposed approach, the best device attains PCE of 17.55%, which is record-high for inorganic tin–lead perovskite solar cells. In addition, treated devices show excellent stability with only 10% and negligible loss after being exposed to 1 sun intensity for 700 h and being stored in N2 after over 4000 h, respectively. Our findings open a new avenue of crystallization route design in inorganic tin–lead perovskites, so as to obtaining high-quality perovskite films and associated solar cells.

High FF: in situ K-doped precursors make large-grain and void-free absorbers. The doping-enhanced Sn diffusion eliminates the local content vibration, suppresses deep level defects, and to higher cell efficiency with greatly improved FF.

This paper proposes a flexible kirigami structure. It has rotating rigid squares and cylindrical shells to improve the flexibility of the structure and produce snap-through instability. First, a mechanical spring model based on a quarter of unit cell was established to predict the mechanical characteristics of its deployment. The elastic deformation energy stored in the mechanical system was calculated, and the applied force was obtained after deriving the displacement. By assuming that the rotational stiffness of the spring is related to the length, elastic modulus, and thickness of the cylindrical shell, the coefficients used to quantify the stiffness of the rotational spring were obtained through a finite element calculation and the mechanical characteristics of the structure were obtained. The accuracy was verified through experiments and the finite element method. Then, the deployment mechanism and parameterization of the structure were analyzed. The snap-through characteristics of the cylindrical shell were analyzed, and the curvature of the second steady state was obtained using the minimum potential energy. The influence of the geometric parameters of the unit cell, such as its length, thickness, and the center angle of the cylindrical shell, on the snap-through instability was analyzed. By stretching or compressing it at different positions, different mechanical characteristics of the deployment were obtained. Finally, based on the designed structure, a stretchable microstrip antenna was designed to achieve high gain while the center frequency remained fixed. An antenna was fabricated and measured, and the test results are in good agreement with the simulated results. This work may provide theoretical guidance for the design and application of deformable structures.

The measuring of the depth profile and electrical activity of implantation impurity in the top nanometer range of silicon encounters various difficulties and limitations, though it is known to be critical in fabrication of silicon complementary metal–oxide–semiconductor (CMOS) devices. In the present work, SRIM program and photocarrier radiometry (PCR) are employed to monitor the boron implantation in industrial-grade silicon in an ultra-low implantation energy range from 0.5 keV to 5 keV. The differential PCR technique, which is improved by greatly shortening the measurement time through the simplification of reference sample, is used to investigate the effects of implantation energy on the frequency behavior of the PCR signal for ultra-shallow junction. The transport parameters and thickness of shallow junction, extracted via multi-parameter fitting the dependence of differential PCR signal on modulation frequency to the corresponding theoretical model, well explain the energy dependence of PCR signal and further quantitatively characterize the recovery degree of structure damage induced by ion implantation and the electrical activation degree of impurities. The monitoring of nm-level thickness and electronic properties exhibits high sensitivity and apparent monotonicity over the industrially relevant implantation energy range. The depth profiles of implantation boron in silicon with the typical electrical damage threshold ( Y ED ) of 5.3 × 10 15 cm −3 are evaluated by the SRIM program, and the determined thickness values are consistent well with those extracted by the differential PCR. It is demonstrated that the SRIM and the PCR are both effective tools to characterize ultra-low energy ion implantation in silicon.

Tin (Sn)-based perovskite solar cells (PSCs) have attracted much attention because they are more environmentally friendly than lead-based PSCs. However, the fast crystallization of Sn-based perovskite films and the easy oxidation of Sn2+ to Sn4+ hinder the improvement of their efficiency and stability. In this work, ethylammonium bromide (EABr) was added to methylammonium tin iodide (MASnI3) perovskite precursor solution to regulate the crystallization dynamics and improve the film morphology. The results show that the large EA+ ions slow down the crystallization process of Sn-based perovskites and form a smooth perovskite film with high crystallinity, while the added Br- anions further improved the crystallinity and orientation of the perovskite film. Under the combined action of EA+ and Br- ions, the as-produced PSCs achieved a champion power conversion efficiency (PCE) of 9.59%. The EABr additive also retarded the oxidation of Sn2+, and the solar cell device maintained 93% of its initial efficiency after 30 days in a nitrogen-filled glove box without being encapsulated. This work provides a new strategy for the realization of high-efficiency Sn-based PSCs.

The surface recombination velocity (SRV), which reflects the fundamental characteristics of surface defects of semiconductor wafers, is an important parameter in evaluating the quality of surface passivation and electrical performance of surface devices. In conventional photocarrier radiometry (PCR) used for characterizing the electronic transport properties of electronically thick silicon wafers, the rear SRV usually cannot be determined directly due to the relatively low sensitivity of PCR signal to the rear SRV. On the other hand, the determination of front SRV is also very sensitive to the experimental measurement error, especially the measurement error of instrumental frequency response, which is not always easy to be accurately measured in the experiment. In this paper, the front and rear SRVs of silicon wafers are extracted simultaneously with high accuracy by a differential PCR via multi-parameter fitting of the experimental frequency dependences of amplitude ratio and phase difference of PCR signals obtained from the regular measurements and measurements with wafers being flipped respectively to a corresponding differential nonlinear PCR model. The comparison between the front and rear SRVs determined by the conventional and differential PCRs indicates that the differential PCR is highly accurate for the simultaneous determination of the front and rear SRVs of silicon wafers.

Despite two-dimensional (2D) Ruddlesden-Popper-phase layered perovskites (RPLPs) exhibiting excellent environmental stability, most solar cells based on 2D RPLP films are fabricated in a controlled inert atmosphere. Meanwhile, the poor charge transport of 2D RPLP films owing to the unfavorable phase arrangement and defects limits the efficiency of 2D RPLP solar cells. Here, we fabricate high-efficiency 2D RPLP solar cells in ambient air assisted by a zwitterion (ZW) additive. We show that the ZW additive suppresses the formation of the bottom 2D phases (n ≤ 2) and the top 3D-like phases in 2D RPLP films. These 2D phases usually grow parallel to the substrate and act as trap sites that inhibit charge transport in the vertical direction. The 3D-like phases, on the other hand, aggravate the long-term stability due to the intrinsic instability of MA+ cations. With improved phase distribution, crystal orientation, and reduced trap states in 2D RPLP films, efficient charge transport is obtained. Finally, a record-high open-circuit voltage (Voc) of 1.19 V and a power conversion efficiency of 17.04% with an enhanced stability are achieved for (BA0.9PEA0.1)2MA3Pb4I13-based (n = 4) solar cells fabricated under high humidity (∼65% RH).