Adaptive fuzzy tracking control for a class of time-varying output constrained nonlinear systems with non-affine nonlinear faults.

This paper investigates a tracking control issue for a class of time-varying output constrained nonlinear systems subject to non-affine nonlinear faults and virtual control coefficients. In the controller design process, the nonlinear function is approximated by fuzzy logic systems. Utilizing a feasible function to convert the system, a new transformation strategy is proposed to handle the system with time-varying output constraints or without output constraints. The mean value theorem is applied to split non-affine faults, and the Nussbaum-type function is used to eliminate the effect of the unknown directional affine variable gain of input resulted from non-affine faults. Combined with adaptive fuzzy backstepping technology and the error transformation function, a new control strategy is presented, which not only deals with the time-varying output constraint but also handles non-affine faults, effectively. Finally, all closed-loop system signals are bounded, and the tracking error can converge to a small preset set. Two simulations are performed to confirm the validity of the presented strategy.

Recent Progress of Low-Toxicity Poor-Lead All-Inorganic Perovskite Solar Cells.

Organic-inorganic hybrid perovskite solar cells (PSCs) have achieved an impressive certified efficiency of 25.7%, which is comparatively higher than that of commercial silicon solar cells (23.3%), showing great potential toward commercialization. However, the low stability and high toxicity due to the presence of volatile organic components and toxic metal lead in the perovskites pose significant challenges. To obtain robust and low-toxicity PSCs, substituting organic cations with pure inorganic cations, and partially or fully replacing the toxic Pb with environmentally benign metals, is one of the promising methods. To date, continuous efforts have been made toward the construction of highly performed low-toxicity inorganic PSCs with astonishing breakthroughs. This review article provides an overview of recent progress in inorganic PSCs in terms of lead-reduced and lead-free compositions. The physical properties of poor-lead all-inorganic perovskites are discussed to unveil the major challenges in this field. Then, it reports notable achievements for the experimental studies to date to figure out feasible methods for efficient and stable poor-lead all-inorganic PSCs. Finally, a discussion of the challenges and prospects for poor-lead all-inorganic PSCs in the future is presented.

B-Site Co-Doping Coupled with Additive Passivation Pushes the Efficiency of Pb-Sn Mixed Inorganic Perovskite Solar Cells to Over 17.

Pb-Sn mixed inorganic perovskite solar cells (PSCs) have garnered increasing interest as a viable solution to mitigate the thermal instability and lead toxicity of hybrid lead-based PSCs. However, the relatively poor structural stability and low device efficiency hinder its further development. Herein, high-performance manganese (Mn)-doped Pb-Sn-Mn-based inorganic perovskite solar cells (PSCs) are successfully developed by introducing Benzhydroxamic Acid (BHA) as multifunctional additive. The incorporation of smaller divalent Mn cations contributes to a contraction of the perovskite crystal, leading to an improvement in structural stability. The BHA additive containing a reductive hydroxamic acid group (O═C-NHOH) not only mitigates the notorious oxidation of Sn2+ but also interacts with metal ions at the B-site and passivates related defects. This results in films with high crystallinity and low defect density. Moreover, the BHA molecules tend to introduce a near-vertical dipole moment that parallels the built-in electric field, thus facilitating charge carrier extraction. Consequently, the resulting device delivers a champion PCE as high as 17.12%, which represents the highest reported efficiency for Pb-Sn-based inorganic PSCs thus far. Furthermore, the BHA molecule provides an in situ encapsulation of the perovskite grain boundary, resulting in significant enhancement of device air stability.

Synergistic Optimization of Buried Interface by Multifunctional Organic-Inorganic Complexes for Highly Efficient Planar Perovskite Solar Cells.

For the further improvement of the power conversion efficiency (PCE) and stability of perovskite solar cells (PSCs), the buried interface between the perovskite and the electron transport layer is crucial. However, it is challenging to effectively optimize this interface as it is buried beneath the perovskite film. Herein, we have designed and synthesized a series of multifunctional organic-inorganic (OI) complexes as buried interfacial material to promote electron extraction, as well as the crystal growth of the perovskite. The OI complex with BF4- group not only eliminates oxygen vacancies on the SnO2 surface but also balances energy level alignment between SnO2 and perovskite, providing a favorable environment for charge carrier extraction. Moreover, OI complex with amine (- NH2) functional group can regulate the crystallization of the perovskite film via interaction with PbI2, resulting in highly crystallized perovskite film with large grains and low defect density. Consequently, with rational molecular design, the PSCs with optimal OI complex buried interface layer which contains both BF4- and -NH2 functional groups yield a champion device efficiency of 23.69%. More importantly, the resulting unencapsulated device performs excellent ambient stability, maintaining over 90% of its initial efficiency after 2000 h storage, and excellent light stability of 91.5% remaining PCE in the maximum power point tracking measurement (under continuous 100 mW cm-2 light illumination in N2 atmosphere) after 500 h.

Event-triggered tracking control of uncertain p-normal nonlinear systems with full-state constraints.

This paper investigates the tracking control problem of uncertain p-normal nonlinear systems with full-state constraints via event-triggered mechanism. By skillful constructing an adaptive dynamic gain and a time-varying event-triggered strategy, a state-feedback controller is proposed to achieve practical tracking. The adaptive dynamic gain is incorporated to deal with the system uncertainties and eliminate the bad effect of the sampling error. A rigorous Lyapunov stability analysis method is put forward to verify that all the closed-loop signals are uniformly bounded and the tracking error converges into a prescribed arbitrary accuracy, and full-state constraints are not violated. Compared with the existing event-triggered strategies, the proposed time-varying event-triggered strategy is low-complexity without designing the hyperbolic tangent function.

Anchoring Vertical Dipole to Enable Efficient Charge Extraction for High-Performance Perovskite Solar Cells.

Perovskite solar cells (PSCs) via two-step sequential method have received great attention in recent years due to their high reproducibility and low processing costs. However, the relatively high trap-state density and poor charge carrier extraction efficiency pose challenges. Herein, highly efficient and stable PSCs via a two-step sequential method are fabricated using organic-inorganic (OI) complexes as multifunctional interlayers. In addition to reduce the under-coordinated Pb2+ ions related trap states by forming interactions with the functional groups, the complexes interlayer tends to form dipole moment which can enhance the built-in electric field, thus facilitating charge carrier extraction. Consequently, with rational molecular design, the resulting devices with a vertical dipole moment that parallels with the built-in electric field yield a champion efficiency of 23.55% with negligible hysteresis. More importantly, the hydrophobicity of the (OI) complexes contributes to an excellent ambient stability of the resulting device with 91% of initial efficiency maintained after 3000 h storage.

Oxalate Pushes Efficiency of CsPb0.7 Sn0.3 IBr2 Based All-Inorganic Perovskite Solar Cells to over 14.

All-inorganic CsPbIBr2 perovskite solar cells (PSCs) have recently gained growing attention as a promising template to solve the thermal instability of organic-inorganic PSCs. However, the relatively low device efficiency hinders its further development. Herein, highly efficient and stable CsPb0.7 Sn0.3 IBr2 compositional perovskite-based inorganic PSCs are fabricated by introducing appropriate amount of multifunctional zinc oxalate (ZnOX). In addition to offset Pb and Sn vacancies through Zn2+ ions incorporation, the oxalate group can strongly interact with undercoordinated metal ions to regulate film crystallization, delivering perovskite film with low defect density, high crystallinity, and superior electronic properties. Correspondingly, the resulting device delivers a champion efficiency of 14.1%, which presents the highest reported efficiency for bromine-rich inorganic PSCs thus far. More importantly, chemically reducing oxalate group can effectively suppress the notorious oxidation of Sn2+ , leading to significant enhancement on air stability.

Pareto-Optimal Strategy for Linear Mean-Field Stochastic Systems With H∞ Constraint.

This article presents results on designing the Pareto-optimal strategy under H∞ constraint for the linear mean-field stochastic systems disturbed by external disturbances. First, combining the stochastic H∞ control theory with the stochastic mean-field theory, we derive the stochastic bounded real lemma (SBRL) of our considered linear mean-field stochastic systems with the stochastic initial condition. Second, we use the mean-field forward-backward stochastic differential equation to solve the mean-field linear quadratic Pareto-optimal problem with indefinite cost functionals. It is proved that the existence of a closed-loop Pareto-optimal strategy is equivalent to the solvability of the coupled generalized differential Riccati equations when some conditions are satisfied. Finally, a necessary and sufficient condition for the Pareto-optimal strategy under the H∞ constraint is researched by four-coupled matrix-valued equations. Besides, we also obtain the Pareto frontier for the mean-field stochastic system with only state-dependent noise. A practical example is presented to show the effectiveness of our main results.

Robust State/Fault Estimation and Fault-Tolerant Control in Discrete-Time T-S Fuzzy Systems: An Embedded Smoothing Signal Model Approach.

This study investigates a simple design method of the robust state/fault estimation and fault-tolerant control (FTC) of discrete-time Takagi-Sugeno (T-S) fuzzy systems. To avoid the corruption of the fault signal on state estimation, a novel smoothing signal model of fault signal is embedded in the T-S fuzzy model for the robust H∞ state/fault estimation of the discrete-time nonlinear system with external disturbance by the traditional fuzzy observer. When the component and sensor faults are generated from different fault sources, two smoothing signal models for component and sensor faults are both embedded in the T-S fuzzy system for robust state/fault estimation. Since the nonsingular smoothing signal model and T-S fuzzy model are augmented together for signal reconstruction, the traditional fuzzy Luenberger-type observer can be employed to robustly estimate state/fault signal simultaneously from the H∞ estimation perspective. By utilizing the estimated state and fault signal, a traditional H∞ observer-based controller is also introduced for the FTC with powerful disturbance attenuation capability of the effect caused by the smoothing model error and external disturbance. Moreover, the robust H∞ observer-based FTC design is transformed into a linear matrix inequality (LMI) -constrained optimization problem by the proposed two-step design procedure. With the help of LMI TOOLBOX in MATLAB, we can easily design the fuzzy Luenberger-type observer for efficient robust H∞ state/fault estimation and solve the H∞ observer-based FTC design problem of discrete nonlinear systems. Two simulation examples are given to validate the performance of state/fault estimation and FTC of the proposed methods.

Boundary Stabilization of Stochastic Delayed Cohen-Grossberg Neural Networks With Diffusion Terms.

This study considers the boundary stabilization for stochastic delayed Cohen-Grossberg neural networks (SDCGNNs) with diffusion terms by the Lyapunov functional method. In the realization of NNs, sometimes time delays and diffusion phenomenon cannot be ignored, so Cohen-Grossberg NNs with time delays and diffusion terms are studied in this article. Moreover, different from the previously distributed control, the boundary control is used to stabilize the system, which can reduce the spatial cost of the controller and is easy to implement. Boundary controllers are presented for system with Neumann boundary and mixed boundary conditions, and criteria are derived such that the controlled system achieves mean-square exponential stabilization. Based on the criterion, the effects of diffusion matrix, coupling strength, coupling matrix, and time delays on exponentially stability are analyzed. In the process of analysis, two difficulties need to be addressed: 1) how to introduce boundary control into system analysis? and 2) how to analyze the influence of system parameters on stability? We deal with these problems by using Poincaré's inequality and Schur's complement lemma. Moreover, mean-square exponential synchronization of stochastic delayed Hopfield NNs with diffusion terms, as an application of the theoretical result, is considered under the boundary control. Examples are given to illustrate the effectiveness of the theoretical results.

Indefinite Mean-Field Stochastic Cooperative Linear-Quadratic Dynamic Difference Game With Its Application to the Network Security Model.

In this article, we show how to obtain all of the Pareto optimal decision vectors and solutions for the finite horizon indefinite mean-field stochastic cooperative linear-quadratic (LQ) difference game. First, the equivalence between the solvability of the introduced N coupled generalized difference Riccati equations (GDREs) and the solvability of the multiobjective optimization problem is established. However, it is difficult to obtain Pareto optimal decision vectors based on the N coupled GDREs because the optimal joint strategy adopted by all players to optimize the performance criterion of some players in the game is different from the strategies of other players, which rely on the weighted matrices of cost functionals that may be different among players. Second, a necessary and sufficient condition is developed to guarantee the convexity of the costs, which makes the weighting technique not only sufficient but also necessary for searching Pareto optimal decision vectors. It is then shown that the mean-field Pareto optimality algorithm (MF-POA) is presented to identify, in principle, all of the Pareto optimal decision vectors and solutions via the solutions to the weighted coupled GDREs and the weighted coupled generalized difference Lyapunov equations (GDLEs), respectively. Finally, a cooperative network security game is reported to illustrate the results presented. Simulation results validate the solvability, correctness, and efficiency of the proposed algorithm.

Unraveling the role of ß1 integrin isoforms in cRGD-mediated uptake of nanoparticles bearing hydrophilized alkyne moieties in epithelial and endothelial cells.

The uptake and trafficking of NPs is impacted by several attributes such as size, shape, surface charge and importantly by surface ligands that can interact with the cell plasma membrane. We envision that NPs which can be readily modified in aqueous environments will be key to engineering patient-specific nanotherapeutics. Towards such systems that can be functionalized "on demand" in aqueous environments, an α-ω epoxy ester monomer that bears an alkyne group at the end of an oligoethylene glycol moiety was designed and synthesized. Copolymerization of this monomer with ε-caprolactone yielded polymers that present hydrophilized alkyne groups along the backbone. This enabled the direct modification of the surface of NPs, as suspensions in aqueous phase, with cell interaction peptides such cyclic-arginine-glycine-aspartic acid (cRGD) using the "click reaction". Uptake of cRGD modified NPs (cRGD-NPs) in human endothelial and tumor epithelial cells revealed that cRGD surprisingly diminished uptake in both tumor epithelial and microvascular endothelial cells by 40-50 percent in comparison to unmodified particles. Probing the mechanism of uptake revealed that the expression pattern of two isoforms of ß1 integrin impacted the uptake of cRGD-NPs differently. While the expression of high molecular weight 140 kDa form of the ß1 integrin enhanced NP uptake, the expression of low molecular 120 kDa form had an inhibitory effect. Furthermore, although, the expression of ß3 integrin was enhanced in endothelial cells and breast cancer epithelial cells, no correlation between ß3 integrin and NP uptake was observed. Additionally, in presence of clathrin and caveolae pathway inhibitors the uptake of cRGD-NPS was in general diminished with a 25-75% decrease in presence of Filipin, a caveolae inhibitor; suggesting a role for lipid rafts in the ß1 integrin-mediated uptake of cRGD-NP NPs. In sum, the polymer system described can be readily adapted to engineer other targeting peptide-based nanotherapeutics, especially for the delivery across difficult penetrate biological barriers such as the blood brain barrier. The main findings of this study have significant implication for the development of integrin targeted nanotherapeutics for anti-tumor therapy.

Intermittent boundary stabilization of stochastic reaction-diffusion Cohen-Grossberg neural networks.

Cohen-Grossberg neural networks (CGNNs) play an important role in many applications and the stabilization of this system has been well studied. This study considers the exponential stabilization for stochastic reaction-diffusion Cohen-Grossberg neural networks (SRDCGNNs) by means of an aperiodically intermittent boundary control. Both SRDCGNNs without and with time-delays are discussed. By employing the spatial integral functional method and Poincare's inequality, criteria are derived to ensure the controlled systems achieve mean square exponential stabilization. Based on these criteria, the effects of diffusion item, control gains, the minimum control proportion and time-delays on exponential stability are analyzed. Examples are given to illustrate the effectiveness of the obtained theoretical results.

Seed-Assisted Growth for Low-Temperature-Processed All-Inorganic CsPbIBr2 Solar Cells with Efficiency over 10.

All-inorganic CsPbIBr2 perovskite has recently received growing attention due to its balanced band gap and excellent environmental stability. However, the requirement of high-temperature processing limits its application in flexible devices. Herein, a low-temperature seed-assisted growth (SAG) method for high-quality CsPbIBr2 perovskite films through reducing the crystallization temperature by introducing methylammonium halides (MAX, X = I, Br, Cl) is demonstrated. The mechanism is attributed to MA cation based perovskite seeds, which act as nuclei lowering the formation energy of CsPbIBr2 during the annealing treatment. It is found that methylammonium bromide treated perovskite (Pvsk-Br) film fabricated at low temperature (150 °C) shows micrometer-sized grains and superior charge dynamic properties, delivering a device with an efficiency of 10.47%. Furthermore, an efficiency of 11.1% is achieved for a device based on high-temperature (250 °C) processed Pvsk-Br film via the SAG method, which presents the highest reported efficiency for inorganic CsPbIBr2 solar cells thus far.

Adaptive Fuzzy Control of Stochastic Nonlinear Systems With Fuzzy Dead Zones and Unmodeled Dynamics.

This paper focuses on an input-to-state practical stability problem for a class of stochastic nonlinear systems with unmodeled dynamics and fuzzy dead zones. A feasible adaptive fuzzy control method is proposed for the developed stochastic system with the slope of dead zone being certain or fuzzy. Based on stochastic small-gain theorem and backstepping technique, the closed-loop system is guaranteed to be input-state-practically stable in probability. The main contributions of this paper lie in that the considered system is more general, and the modified Lemma 2 makes the presentation of the formulas in lemma consistent with their application forms. Finally, two simulation examples are provided to demonstrate the effectiveness of the proposed approach.

Mechanism of Water Effect on Enhancing the Photovoltaic Performance of Triple-Cation Hybrid Perovskite Solar Cells.

The water effect on the performance of perovskite solar cells has been intensively studied in recent years. However, the conflicting conclusions derived from different studies make it impossible to fully understand the mechanism involved. Besides, all studies have concentrated on single methylammonium cation perovskites. As a consequence, the effects of water on formamidinium and cesium perovskites are still unclear. Herein, we introduce water during the fabrication of triple-cation hybrid perovskites. By controlling the water content, we demonstrate that an optimal concentration of water contributes to a better crystallized and more uniform hybrid perovskite film without impurities, resulting in significant enhancement in power conversion efficiency and long-term stability. In addition, two forms of water (hydrate water and bulk water) are found in the hybrid perovskite film. Hydrate water induces a recrystallization process, whereas bulk water leads to decomposition of the perovskite. These distinct phases are considered to form the basic mechanism affecting the performance of the cells.

Thermal Stability-Enhanced and High-Efficiency Planar Perovskite Solar Cells with Interface Passivation.

As the electron transport layer (ETL) of perovskite solar cells, oxide semiconductor zinc oxide (ZnO) has been attracting great attention due to its relatively high mobility, optical transparency, low-temperature fabrication, and good environment stability. However, the nature of ZnO will react with the patron on methylamine, which would deteriorate the performance of cells. Although many methods, including high-temperature annealing, doping, and surface modification, have been studied to improve the efficiency and stability of perovskite solar cells with ZnO ETL, devices remain relatively low in efficiency and stability. Herein, we adopted a novel multistep annealing method to deposit a porous PbI2 film and improved the quality and uniformity of perovskite films. The cells with ZnO ETL were fabricated at the temperature of <150 °C by solution processing. The power conversion efficiency (PCE) of the device fabricated by the novel annealing method increased from 15.5 to 17.5%. To enhance the thermal stability of CH3NH3PbI3 (MAPbI3) on the ZnO surface, a thin layer of small molecule [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) was inserted between the ZnO layer and perovskite film. Interestingly, the PCE of PCBM-passivated cells could reach nearly 19.1%. To our best knowledge, this is the highest PCE value of ZnO-based perovskite solar cells until now. More importantly, PCBM modification could effectively suppress the decomposition of MAPbI3 and improve the thermal stability of cells. Therefore, the ZnO is a promising candidate of electron transport material for perovskite solar cells in future applications.