Hyperbolic media are well known for converting high k-components that are evanescent in conventional dielectrics into propagating bulk waves through their open equifrequency contours. Here, we reveal a complementary temporal effect: after a sudden transition into an effectively nondispersive hyperbolic state, conservation of the full wavevector causes the indefinite dispersion to partition momentum space into real-, zero-, and purely imaginary-frequency regimes. Consequently, p-polarized waves undergo conventional temporal scattering, critical magnetic-field freezing, or exponential growth and decay, depending solely on their conserved wavevector direction, whereas s-polarized waves remain in the real-frequency regime. A second temporal boundary releases the frozen or amplified fields into propagating waves at original frequency. Analytical temporal boundary theory, k-space pulse reconstruction, and finite-difference time-domain simulations corroborate these dynamics. These results establish hyperbolic temporal boundaries as a compact route to direction-selective imaginary frequency dynamics and wave amplification without Floquet periodicity.

Ultra‐flexible perovskite solar cells (UF‐PSCs) with superior power‐to‐weight ratio have enormous application potential in the aerospace field. However, structural integrity and functional stability of UF‐PSCs remains a significant challenge under such extreme conditions, which are mainly caused by insufficient bonding and thus damage of the physically‐contact‐only perovskite buried interfaces. Herein, to solve this problem, imidazole bromide (IMBr) interface linker with bilateral linking ability is employed to harmonize the bonding between perovskite and substrate. It is demonstrated that the imidazole cations can anchor to poly(3,4‐ethlenedioxythiophene) polystyrene sulfonate through hydrogen bonds and connect to Pb‐I by coordination bonds, resulting in low‐defect and robust perovskite‐substrate interface at the same time. The interfacial tensile test reveals that the tensile resistance of the buried interface is increased by 2.76 times, which will directly improve the ultimate bending resistance of UF‐PSCs. Finally, the strategy increased the power conversion efficiency (PCE) of UF‐PSCs from 16.87% to 20.45%, the highest efficiencies reported so far. The UF‐PSCs demonstrates unprecedented bending stability after extreme deformation, retaining 82.4% and 89.4% of their initial PCEs after 10,000 and 200 cycles at radii of 0.5 and 0.25 mm, respectively. This work advances the potential application of UF‐PSCs in the aerospace sector.

Self-assembled molecules (SAMs) have served as a pivotal interfacial engineering enabler for advancing the performance of perovskite solar cells. However, the spontaneous aggregation of SAMs leads to uneven deposition, particularly in the fabrication of large-area perovskite solar modules (PSMs) by blade-coating. Here, a co-adsorption strategy utilizing 3-amino-1-propanesulfonic acid (3NS) is proposed as a blade-coating-compatible strategy to achieve a uniform SAMs anchoring across a 10 x 10 cm2 substrate. Acting as a co-adsorbate with SAMs, 3NS leverages synergistic multiple intermolecular interactions-such as electrostatic forces, hydrogen bonding, and cation-pi interactions-to effectively disrupt the aggregation of SAMs, enabling their high-density anchoring on NiOx substrate. Meanwhile, the 3NS-SAMs co-adsorption layer system optimizes interfacial energy level alignment and passivates defects. By virtue of this co-adsorption strategy, the PSM achieves a champion power conversion efficiency (PCE) of 20.16% (active area: 63.09 cm2). Moreover, the modules retain 87.64% and 72.70% of their initial PCE after 1100 h of ambient aging and 264 h of continuous thermal aging at 80 degrees C, respectively. This work presents a scalable blade-coating-compatible strategy for controlling the deposition of SAMs, advancing the development of high-performance PSMs.

The two-step sequential deposition process has been widely employed to fabricate perovskite solar cells (PSCs). However, the random orientation of lead iodide (PbI2) template and undesirable PbI2 residues resulting from the rapid and unregulated solid-liquid reaction poses a significant challenge to achieving high performance and long-term stability of two-step processed PSCs. Here, l-ascorbic acid sodium salt (l-AASS) was introduced into the lead iodide (PbI2) precursor solution to delicately control the FAPbI3 crystallization kinetics behavior via manipulating the arrangement mode of mesoporous PbI2 template, which provides a more favorable foundation for the subsequent infiltration and reaction of organic salts. Comprehensive characterization demonstrates that the interaction between l-AASS and PbI2 promotes the preferential orientation and a significant reduction in residual PbI2 due to the formation of the l-AASS/PbI2 complex, further enabling rapid formation of high-quality α-FAPbI3 perovskite films with larger grains at an earlier stage. Additionally, l-AASS effectively passivated the uncoordinated Pb2+ defects and reduced the nonradiative recombination sites in perovskite films. These synergistic factors holistically contribute to the remarkable improvement in PSCs performance; an encouraging power conversion efficiency (PCE) of 25.23% was achieved with impressive stability. Moreover, a PCE of 20% was obtained for large-area (65 cm2) modules, confirming the upscale potential of current premodulating PbI2 precursor strategy for industrial commercialization.

The doping level of 2,2′,7,7′‐tetrakis[N,N‐di(4‐methoxyphenyl)amino]‐9,9′‐spirobifluorene (Spiro‐OMeTAD), a commonly used hole transport layer in perovskite solar cells (PSCs), is crucial for its electrical conductivity and the final photovoltaic performance. The routine oxygen‐oxidation doping strategy falls short in achieving high‐level doping due to the sparsity and random distribution of dopants within the solid Spiro‐OMeTAD film. Here the use of carbon nanohorns (CNH) as a promoter to significantly enhance the doping level of Spiro‐OMeTAD is reported. The unique asymmetry and polar structure of CNH not only enable effective charge transfer between CNH and Spiro‐OMeTAD, also exhibit confinement effect to trap Li + ions and O 2 , promoting the consecutive chemical doping processes. Corresponding carbon‐based PSCs achieved a power conversion efficiency of 23.24% (22.51% certified), and demonstrated exceptional long‐term durability, retaining 95.3% of the initial PCE (power conversion efficiency) after 1500 h of tracking at maximum power point (MPP) under 100 mW cm −2 illumination.

The sol–gel method is efficient and cost‐effective for synthesizing SnO2 sol, wherein SnO2 nanocrystallites (NCs) are stabilized by electric double‐layer of solvated ions tightly bound to their surface. However, this strong binding makes the removal of electric double‐layer residues from the SnO2 electron transport layer (ETL) to be difficult at low temperatures. This hinders both the close contact and subsequent growth among adjacent SnO2 NCs, leading to severe carriers scattering at grain boundary, adversely affecting the electrical properties of SnO2 ETL. Herein, SnO2 sol is synthesized via an ethanol‐based sol–gel method and aqueous ammonia (NH3·H2O) is introduced to effectively clean stubborn electric double‐layer residues within the SnO2 ETL at a low temperature (80 °C). Removing residues reduces the gap among adjacent SnO2 NCs and promotes further reconstructed growth through oriented attachment (OA), thereby reducing the number of grain boundaries. Hence, the energy barriers for electron transport decrease within the SnO2 ETL. Furthermore, MHP prepared on the treated ETL has fine‐tuned energy level alignment, improving the electron extraction capacity. Consequently, flexible perovskite solar cells (f‐PSCs) incorporating this ETL achieved a notable increase in power conversion efficiency, rising from 19.16% to 23.71%, as well as superior mechanical stability.

Advanced photovoltaics, such as ultra-flexible perovskite solar cells (UF-PSCs), which are known for their lightweight design and high power-to-mass ratio, have been a long-standing goal that we, as humans, have continuously pursued. Unlike normal PSCs fabricated on rigid substrates, producing high-efficiency UF-PSCs remains a challenge due to the difficulty in achieving full coverage and minimizing defects of metal halide perovskite (MHP) films. In this study, we utilized Al2O3 nanoparticles (NPs) as an inorganic surface modifier to enhance the wettability and reduce the roughness of poly-bis(4-phenyl) (2,4,6-trimethylphenyl) amine simultaneously. This approach proves essentials in fabricating UF-PSCs, enabling the deposition of uniform and dense MHP films with full coverage and fewer defects. We systematically investigated the effect of Al2O3 NPs on film formation, combining simulation with experiments. Our strategy not only significantly increases the power conversion efficiency (PCE) from 11.96% to 16.33%, but also promotes reproducibility by effectively addressing the short circuit issue commonly encountered in UF-PSCs. Additionally, our UF-PSCs demonstrates good mechanical stability, maintaining 98.6% and 79.0% of their initial PCEs after 10,000 bending cycles with radii of 1.0 and 0.5 mm, respectively.

Vacuum deposition is promising for large-area, high-throughput production of perovskite solar cells (PSCs). However, the strict low humidity control increases the costs for manufacturing facilities and hinders the large-scale production of PSCs. In this work, a sequential deposition method was used to prepare the perovskite intermediate phase, and the impact of ambient humidity was studied during the annealing process. It is shown that proper humidity has a positive effect on the perovskite layer, which is conducive to accelerate the reaction between organic salts and PbI2 and improve the surface morphology of the film. The perovskite annealing under 55% relative humidity exhibits fewer defects and faster carrier transport kinetics. The resulting PSCs, with all layers fabricated adopting vapor deposition, yield a power conversion efficiency (PCE) of 15.01% for the large area modules of 100 cm2 (active area 64.8 cm2). More impressively, the PCE of the unpackaged cell modules remained above 80% after being placed in ambient air for 1200 h. The results open a promising way for scalable fabrication of humidity-tolerant large-area perovskite solar cell modules and shed light on the industrial production of PSCs.

Eliminating surface defects and impurities on metal halide perovskite (MHP) films through chemical reactions represents a novel strategy to improve the performance of perovskite solar cells (PSCs), which can be referred to as "chemical polishing". This approach is anticipated to be more facile, precise, and distinct from the extensively documented surface passivation methods in terms of its underlying mechanism. However, to date, the underlying selective chemical reaction mechanism still requires in-depth study. In this context, we present a novel two-step chemical polishing method that eliminates surface impurities while simultaneously passivating the sub-surface. The core principle of this method involves two primary steps: (1) the creation of two-dimensional (2D) perovskite via selective reactions between polishing agents (n-octylammonium bromide, OABr) and undesired metastable amorphous species, as well as residual PbI2 nanocrystals present on the surface of MHP films. (2) Subsequently, the 2D perovskite and excess polishing agents are efficiently eliminated using a mixed solvent. Following the polishing process, the sub-surface, which is passivated by residual OABr, contains fewer defects and can establish improved electrical contact with the hole transport layer (HTL). As a result, the power conversion efficiency (PCE) of PSCs is enhanced from 21.7% to 23.6%. Moreover, the PSCs processed with chemical polishing exhibit enhanced long-term operational stability, with a capability to retain 80.2% of their original PCE value after 1500 h of illumination.

In the landscape of photovoltaic research, carbon-based perovskite solar cells (C-PSCs) have attracted widespread attention due to their outstanding stability. However, compared to metal-based PSCs, their power conversion efficiency (PCE) lags markedly behind. The key lies in two primary factors: First, the inefficiency of the carbon electrode in transporting and collecting carriers; second, the energy level mismatch with adjacent functional layers. These problems increase both the charge transport resistance and the charge injection barriers, thereby diminishing the overall efficiency of the device. In this study, an effective strategy is presented to tackle this issue by developing modular C-PSCs that utilize dual carbon electrodes and implement multiscale modulation. This approach specifically focuses on three crucial aspects: establishing a highly conductive network, ensuring sufficient interfacial contact, and achieving well-matched energy band alignment. By synergistically incorporating 0D carbon black (CB) and 1D carbon nanotube (CNT) into dual carbon electrodes, a resilient conductive network with enhanced interfacial contact is established, creating favorable conditions for efficient carrier transfer. Additionally, the energy level structure of CB is meticulously adjusted at the molecular scale by introducing individually adsorbed titanium (Ti) atoms, effectively addressing the energy level mismatch with the hole transport layer (spiro-OMeTAD), and notably reducing the charge injection barrier at the interface. Based on the above strategy, the PCE of the C-PSCs has undergone a remarkable enhancement from 15.27% to 22.45%. Moreover, the device shows excellent stability, with its PCE retaining over 95% of the initial value even after 1000 h of continuous operation under one-sun intensity. This manuscript improves interfacial contact and optimizes charge transport pathways by constructing a multidimensional dual-carbon electrode structure. At the same time, it employs a single-atom modification strategy to optimize energy level alignment and accelerate carrier transport dynamics, thereby achieving the fabrication of highly efficient and stable carbon-based perovskite solar cells. image

Perovskite solar cells (PSCs) have led to distinguished achievements and become one of the state-of-the-art photovoltaic technologies. Undoubtedly, reliable preparation of large area high-quality perovskite (PVK) films with uniform optoelectronic properties has become a critical and challenging task to transition PSCs from lab to market. Here, methyldiphenylphosphine oxide (MDPPO) is employed as an additive in a PVK precursor solution to promote uniform conductivity and carrier transport of PVK films. More important, to check its compatibility with the upscaling process, the MDPPO additive strategy was further applied to doctor-blade large-area PVK films. As a result, benefit from the favorable role of MDPPO additive, the power conversion efficiencies (PCEs) of small-area PSCs reach 23.85% with superb open circuit voltage (Voc) of 1.15 V and fill factor of 81.21%, while an impressive PCE of 19.22% was achieved for the large-area PSC minimodules with active area of 61.48 cm2. Remarkably, the MDPPO modified device exhibits significantly improved operational stability, maintaining an initial efficiency of 68% even after 750 h under continuous 1-sun illumination. Our achievements will provide profound insight and further guidance for the scale-up process of PSCs from lab to large-scale modules.

The vibration signals of the bearings of coal mine machanical equipment under the working conditions of strong impact and heavy load show strong transient non-stationary and local nonlinear features. It is difficult to identify the fault features by the classical time-domain statistical analysis method and the global domain transformation method. The traditional order tracking method has the problems of inconvenient equipment installation and difficulty in obtaining instantaneous frequency. The traditional keyless phase order tracking method estimates the instantaneous frequency with low precision under the condition of severe speed fluctuation. This leads to poor fault identification effect. To solve these problems, a new method of bearing fault diagnosis based on harmonic matching compensation and keyless phase order tracking is proposed. Firstly, the time-frequency analysis method based on harmonic matching compensation is used to process the bearing vibration signal and estimate the instantaneous frequency accurately. Secondly, the Vold-Kalman filtering method is used to adaptively extract the harmonic component signal. Thirdly, the Hilbert transform is used to calculate the instantaneous phase of the harmonic. The mapping relationship between the time domain and angle domain is obtained, so as to complete the resampling of the original time domain signal in the angle domain. Finally, the resampled signals are processed by fast Fourier transform (FFT). The fault features of the bearing are identified by analyzing the envelope order spectrum. The simulation and experimental results show that the maximum relative error between the estimated instantaneous frequency and the actual value is less than 1%. The feature order of bearing fault is accurate and obvious, which can effectively diagnose the bearing fault.

Flexible perovskite solar cells (f‐PSCs) show great promise in portable‐power applications (e.g., chargers, drones) and low‐cost, scalable productions (e.g., roll‐to‐roll). However, in conventional n–i–p architecture f‐PSCs, the low‐temperature processed metal oxide electron transport layers (ETLs) usually suffer from high resistance and severe defects that limit the power conversion efficiency (PCE) improvement of f‐PSCs. Besides the enhancement in the mobility of metal oxide and passivation for perovskite/ETL interfacial defects reported in previous literature, herein, the electron transport loss between the metal oxide nanocrystallines within the ETL is studied by introducing an amorphous F‐doped TiO x (F‐TiO x ) caulked crystalline SnO 2 composite ETL. The F‐TiO x in this novel composite ETL acts as an interstitial medium between adjacent SnO 2 nanocrystallines, which can provide more electron transport channels, effectively passivate oxygen vacancies, and optimize the energy level arrangement, thus significantly enhancing the electron mobility of ETL and reducing the charge transport losses. The composite ETL‐based f‐PSCs achieve a high PCE of 22.70% and good operational stability. Furthermore, a moderate roughness of the composite ETL endows f‐PSCs with superior mechanical reliability by virtue of a strong coupling at the ETL/perovskite interface, by which the f‐PSCs can maintain 82.11% of their initial PCE after 4000 bending cycles.

Perovskite solar cells (PSCs) as an emerging photovoltaic technique have achieved exceptional power conversion efficiency (PCE) up to 25.7% after fast development over the past decade. But currently some critical issues are still not well addressed in terms of realizing large-scale fabrication, for example, fast fabrication of high-quality perovskite film with good stability. Here, we demonstrate the use of stable and fast-crystallizing low-dimensional (LD) perovskite thin films as the light absorber with only a 10 s annealing time at 250 degrees C, delivering a PCE of 18.16%. The crystallization and photoelectric properties of LD perovskite are well illustrated. The reduction in the annealing time will dramatically increase the productivity of PSCs. The PSCs based on rapidly annealed LD perovskite thin films exhibit excellent stability, with only 12% loss of PCE after 1000 h storage at 85 degrees C and 40-70% relative humidity.

Antisolvent engineering is routinely used to modulate the crystallization of perovskite films as they can offer an additional driving force for nucleation. Actually, the intervention of antisolvent into nucleation is thought to involve some relatively fast and complex processes, which, however, are not fully understood so far. Here, the diffusion of the organic amine cation FA+ (one dominated precursor) and its distribution in a spin-coating process in different antisolvents is simulated by the computational fluid dynamics (CFD) model. It is suggested that a moderate diffusion rate (like that in the case of toluene as an antisolvent) not only enables to form a very uniform distribution of FA+ ions on the substrate, beneficial to the uniform nucleation of the intermediate phase, but also can balance the nucleation and growth rates of the intermediate phase, thereby suppressing undesired heterogeneous nucleation and growth. Results show that the perovskite film fabricated using toluene as an antisolvent has a high quality, based on which higher power conversion efficiencies of up to 24.32% are achieved for perovskite solar cells.

基于变换光学的幻象光学器件能够表现出自然界中不存在的现象,如隐身、超散射和隐形门等.其中电磁超散射现象利用变换光学中的折叠几何变换,使得物体的散射截面远大于其几何截面,颠覆了人们对于传统散射中散射截面通常小于散射体几何截面的认知.这一现象也为现实中实现"穿墙术"提供了可能.文章着重介绍了基于变换光学的超散射的发展历程以及利用超散射实现隐形门的方法.隐形门在自由空间的实现为将来幻象器件的设计提供了新的思路.

Varying working condition leads to the data distributions offset between training (source domain) and testing (target domain), which results in insufficient capability of traditional intelligent recognition methods for rotating machinery. Aiming at this problem, a novel intelligent recognition method based on adversarial domain adaptation convolutional neural network (ADACNN) is proposed for bearing faults. First, a weight-sharing convolutional neural network (CNN) is constructed to map training data from both source and target domains to a feature and predicted label spaces, respectively. Then, adversarial learning and maximum mean discrepancy (MMD) are separately introduced in the feature and predicted label space for domain adaptation, and the ADACNN model is established. Finally, a method based on ADACNN, which can realize domain adaptation in two different spaces, is proposed for intelligent recognition of bearing faults. The proposed method is validated by various cross-domain bearing fault recognition tasks under variable speeds and loads. Compared with shallow models, CNN, and commonly used domain adaptation methods, the proposed method has more than a 4% fault recognition accuracy advantage under varying working conditions.

Pulley group plays an important role in the transmission of large mechanical equipment. To obtain informative data for condition monitoring, it is very important to optimize sensor placement on the pulley group. However, due to sharp speed fluctuation, heavy load and complex internal structure, sensor placement for acquiring optimal monitoring points is still a challenging task. Therefore, a novel sensor optimization method based on data fusion is proposed. In this method, the Kalman filter is firstly used to refine the collected signal for dealing with the variable noises. Subsequently, the variable periodicity strength of the signal is calculated to recognize the non-stationary characteristics of the measured signal. A data fusion technique based on maximum likelihood estimation (MLE) is then introduced to estimate sensitive components from the multi-source sensor signals for finding out optimal sensor placement points. The method is validated experimentally on a test rig of the pulley group with variable speed conditions. Analysis results show that the proposed method can recognize the optimal sensor placement points for the pulley group.

For perovskite solar cells (PSCs), the presence of interfacial defects limits device’s efficiency and long-term stability. Reasonably passivating the interfacial defects and reducing the non-radiative recombination concerning perovskite layer are effective ways to achieve high-efficiency PSCs. Herein, we report an effective method by using an asymmetric diammonium salt of N, N-dimethyl-1,3-propanediamine dihydroiodide (DMAPAI2) buried in SnO2 layer to modify the interface between electron transport layer (ETL) and perovskite (PVK) layer. The burying of DMAPAI2 into SnO2 not only improves the electron mobility of SnO2 ETL, but also optimizes the energy level arrangement of ETL/PVK interface. In addition, the crystallinity of PVK is enhanced and the defects at the buried interface are passivated. Based on this strategy, the power conversion efficiency (PCE) of PSCs is significantly improved from 20.78% to 23.20%. Meanwhile, as compared to the control device, the DMAPAI2 modified PSCs exhibited better operational stability under 1-sun illumination at maximum power point, and retained over 85% of its initial PCE after 1200 h continuous irradiation. These results indicate that burying suitable ammonium salt in ETL is an effective interfacial modification strategy to boost the device’s PCE and stability.

Suffering from sluggish charge transfer kinetics, carbon‐based perovskite solar cells (C‐PSCs) lag far behind the Ag/Au‐based normal PSCs in power conversion efficiency (PCE). Herein, the use of defective multi‐walled CNT (D‐MWCNT) is demonstrated to tune the charge transfer kinetics regarding hole transport layer (HTL) and the interface between HTL and carbon electrode. Benefiting from the electrostatic dipole moment interaction between the terminal oxygen‐containing groups of D‐MWCNT and 2,2′,7,7′‐tetrakis( N , N ‐di‐p‐methoxyphenylamine)‐9,9′‐spirobifluorene, an interface coupling at molecular level is established and in turn, allows rapid charge transfer by edge effect induced electron redistribution and 1D hyper‐channels. Meanwhile, a seamless connection between HTL and carbon electrode is achieved in a novel modular C‐PSCs due to D‐MWCNT induced interface coupling with graphene at nanometer scale. Based on this strategy, high PCEs up to 22.07% (with a certified record PCE of 21.9% to date for C‐PSCs) and excellent operational stability have been achieved.