Inhibiting perovskite decomposition by a creeper-inspired strategy enables efficient and stable perovskite solar cells.

The commercialization of perovskite solar cells is badly limited by stability, an issue determined mainly by perovskite. Herein, inspired by a natural creeper that can cover the walls through suckers, we adopt polyhexamethyleneguanidine hydrochloride as a molecular creeper on perovskite to inhibit its decomposition starting from the annealing process. The molecule possesses a long-line molecular structure where the guanidinium groups can serve as suckers that strongly anchor cations through multiple hydrogen bonds. These features make the molecular creeper can cover perovskite grains and inhibit perovskite decomposition by suppressing cations' escape. The resulting planar perovskite solar cells achieve an efficiency of 25.42% (certificated 25.36%). Moreover, the perovskite film and device exhibit enhanced stability even under harsh damp-heat conditions. The devices can maintain >96% of their initial efficiency after 1300 hours of operation under 1-sun illumination and 1000 hours of storage under 85% RH, respectively.

Minimizing Voltage Losses via Synergistically Reducing Hetero-Interface Energy Offset for High Efficiency Perovskite Solar Cells.

The open circuit voltage (VOC) losses at multiple interfaces within perovskite solar cells (PSCs) limit the improvements in power conversion efficiency (PCE). Herein, a tailored strategy is proposed to reduce the energy offset at both hetero-interfaces within PSCs to decrease the VOC losses. For the interface of perovskite and electron transport layer where exists a mass of defects, it uses the pyromellitic acid to serve as a molecular bridge, which reduces non-radiative recombination and energy level offset. For the interface of perovskite and hole transport layer, which includes a passivator of PEAI, the detrimental effect (negative shift of work function) of PEAI passivation and optimizing the interface energy level alignment are neutralized by incorporating (2-(4-(bis(4-methoxyphenyl)amino)phenyl)-1-cyanovinyl)phosphonic acid. Owing to synergistically reduced hetero-interface energy offset, the PSCs achieve a PCE of 25.13%, and the VOC is increased from 1.134 to 1.174 V. In addition, the resulting PSCs possess enhanced stability, the unencapsulated PSCs can maintain ≈96% and ≈97% of their initial PCE after 2000 h of aging under ambient conditions and 210 h under operation conditions.

Cascade Reaction in Organic Hole Transport Layer Enables Efficient Perovskite Solar Cells.

The doped organic hole transport layer (HTL) is crucial for achieving high-efficiency perovskite solar cells (PSCs). However, the traditional doping strategy undergoes a time-consuming and environment-dependent oxidation process, which hinders the technology upgrades and commercialization of PSCs. Here, we reported a new strategy by introducing a cascade reaction in traditional doped Spiro-OMeTAD, which can simultaneously achieve rapid oxidation and overcome the erosion of perovskite by 4-tert-butylpyridine (tBP) in organic HTL. The ideal dopant iodobenzene diacetate was utilized as the initiator that can react with Spiro to generate Spiro⋅+ radicals quickly and efficiently without the participation of ambient air, with the byproduct of iodobenzene (DB). Then, the DB can coordinate with tBP through a halogen bond to form a tBP-DB complex, minimizing the sustained erosion from tBP to perovskite. Based on the above cascade reaction, the resulting Spiro-based PSCs have a champion PCE of 25.76 % (certificated of 25.38 %). This new oxidation process of HTL is less environment-dependent and produces PSCs with higher reproducibility. Moreover, the PTAA-based PSCs obtain a PCE of 23.76 %, demonstrating the excellent applicability of this doping strategy on organic HTL.

Inhibition of ion diffusion/migration in perovskite p-n homojunction by polyetheramine insert layer to enhance stability of perovskite solar cells with p-n homojunction structure.

Perovskite p-n homojunctions (PHJ) have been confirmed to play a crucial role in facilitating carrier separation/extraction in the perovskite absorption layer and provide an additional built-in potential, which benefits the inhibition of carrier recombination in perovskite solar cells (PSCs) and ultimately improves device performance. However, the diffusion and migration of ions between n-type and p-type perovskite films, particularly under operational and heating conditions, lead to the degradation of PHJ structures and limit the long-term stability of PSCs with PHJ structure (denoted as PHJ-PSCs). In this study, we propose an insert layer strategy by directly introducing an ultra-thin polyetheramine (PEA) layer between the n-type and p-type perovskite films to address those challenges arising from ion movements. Femtosecond transient absorption (fs-TAS) and photoluminescence (PL) measurements demonstrate that the PHJ (without and with the insert layer) enhances carrier separation/extraction compared to the single n-type perovskite film. Monitoring the evolution of bromine element distribution reveals that the insert layer can efficiently suppress ion diffusion between perovskite films, even under long-term illumination and heating conditions. Consequently, an efficiency of 23.53% with excellent long-term operational stability is achieved in the optimized PHJ-PSC with the insert layer.

Oriented Molecular Bridge Constructs Homogeneous Buried Interface for Perovskite Solar Cells with Efficiency Over 25.3.

Buried interface optimization matters the efficiency improvement of planar perovskite solar cells (PSCs), and the molecular bridge is reported to be an effective approach. Herein, a molecular bridge is constructed at buried interface using 4-chloro-3-sulfamoylbenzoic acid (CSBA), and its preferred arrangement is systematically investigated. It is elucidated that the CSBA molecular is prone to be orientationally absorbed on TiO2 surface through COOH-Ti, and then connect with perovskite through S═O-Pb, resulting in a feasible oriented molecular bridge. Contributing to the passivated interfacial defects, optimized interfacial energy level, and released perovskite tensile stress, resulting from the oriented CSBA molecular bridge, the PSCs with an active area of 0.08 cm2 achieve a certified power conversion efficiency (PCE) of 25.32%, the highest among the TiO2-based planar PSCs. Encouragingly, the PSCs with an active area of 1 cm2 achieve a champion PCE of 24.20%, significantly promoting the efficiency progress of large-area PSCs. In addition, the PSCs with oriented CSBA molecular bridge possess enhanced stability, the unencapsulated PSCs can maintain ≈91% and ≈85% of their initial PCE after 3000 h aging under ambient condition and 1200 h aging under exposure to UV irradiation.

In situ surface regulation of 3D perovskite using diethylammonium iodide for highly efficient perovskite solar cells.

Surface passivation by constructing a 2D/3D structure is considered to be an effective strategy for suppressing non-radiative recombination and improving the device efficiency and stability. Herein, the 2D perovskite is formed in situ on the surface of a 3D perovskite via chemical interactions between diethylammonium iodide (DAI) and Pb-I octahedra, which greatly reduces the deep level defects and non-radiative recombination. Moreover, the 2D/3D structure can regulate the energy level alignment, enhance the charge extraction, and improve the open-circuit voltage. Finally, compared with the control device, the power conversion efficiency (PCE) of the DAI-treated device increases from 21.58 to 23.50%. The unencapsulated devices stored in air for more than 500 hours can still retain 97% of their initial PCE, revealing good long-term placement stability. This work provides a promising strategy to fabricate efficient PSCs through the in situ construction of 2D/3D perovskite heterojunctions.

Impact of Precursor Concentration on Perovskite Crystallization for Efficient Wide-Bandgap Solar Cells.

High-crystalline-quality wide-bandgap metal halide perovskite materials that achieve superior performance in perovskite solar cells (PSCs) have been widely explored. Precursor concentration plays a crucial role in the wide-bandgap perovskite crystallization process. Herein, we investigated the influence of precursor concentration on the morphology, crystallinity, optical property, and defect density of perovskite materials and the photoelectric performance of solar cells. We found that the precursor concentration was the key factor for accurately controlling the nucleation and crystal growth process, which determines the crystallization of perovskite materials. The precursor concentration based on Cs0.05FA0.8MA0.15Pb(I0.84Br0.16)3 perovskite was controlled from 0.8 M to 2.3 M. The perovskite grains grow larger with the increase in concentration, while the grain boundary and bulk defect decrease. After regulation and optimization, the champion PSC with the 2.0 M precursor concentration exhibits a power conversion efficiency (PCE) of 21.13%. The management of precursor concentration provides an effective way for obtaining high-crystalline-quality wide-bandgap perovskite materials and high-performance PSCs.

Transition dynamics and optogenetic controls of generalized periodic epileptiform discharges.

This paper aims to analyze possible mechanisms underlying the generation of generalized periodic epileptiform discharges (GPEDs), especially to design targeted optogenetic regulation strategies. First and foremost, inspired by existing physiological experiments, we propose a new computational framework by introducing a second inhibitory neuronal population and related synaptic connections into the classic Liley mean field model. The improved model can simulate the basic normal and abnormal brain activities mentioned in previous studies, but much to our relief, it perfectly reproduces some types of GPEDs that match the clinical records. Specifically, results show that disinhibitory synaptic connections between inhibitory interneuronal populations are closely related to the occurrence, transition and termination of GPEDs, including delaying the occurrence of GPEDs caused by the excitatory AMPAergic autapses and regulating the transition process of GPEDs bidirectionally, which support the conjecture that selective changes of synaptic connections can trigger GPEDs. Additionally, we creatively offer six optogenetic strategies with dual targets. They can all control GPEDs well, just as experiments reveal that optogenetic stimulation of inhibitory interneurons can suppress abnormal activities in epilepsy or other brain diseases. More importantly, 1:1 coordinated reset stimulation with one period rest is concluded as the optimal strategy after taking into account the energy consumption and control effect. Hope these results provide feasible references for pathophysiological mechanisms of GPEDs.

Dynamic Transitions of Epilepsy Waveforms Induced by Astrocyte Dysfunction and Electrical Stimulation.

Experimental studies have shown that astrocytes participate in epilepsy through inducing the release of glutamate. Meanwhile, considering the disinhibition circuit among inhibitory neuronal populations with different time scales and the feedforward inhibition connection from thalamic relay nucleus to cortical inhibitory neuronal population, here, we propose a modified thalamocortical field model to systematically investigate the mechanism of epilepsy. Firstly, our results show that rich firing activities can be induced by astrocyte dysfunction, including high or low saturated state, high- or low-frequency clonic, spike-wave discharge (SWD), and tonic. More importantly, with the enhancement of feedforward inhibition connection, SWD and tonic oscillations will disappear. In other words, all these pathological waveforms can be suppressed or eliminated. Then, we explore the control effects after different external stimulations applying to thalamic neuronal population. We find that single-pulse stimulation can not only suppress but also induce pathological firing patterns, such as SWD, tonic, and clonic oscillations. And we further verify that deep brain stimulation can control absence epilepsy by regulating the amplitude and pulse width of stimulation. In addition, based on our modified model, 3 : 2 coordinated reset stimulation strategies with different intensities are compared and a more effective and safer stimulation mode is proposed. Our conclusions are expected to give more theoretical insights into the treatment of epilepsy.

Control analysis of electrical stimulation for epilepsy waveforms in a thalamocortical network.

Physiological experiments and computational models both show that the thalamic reticular nucleus (RE) participates in inducing various firing patterns of cortex. Absence seizure, featured by 2-4 Hz spike-wave discharges (SWD) oscillation, is a high incidence of disease in children. Lots of electrophysiological experiments have verified the correlation between absence seizures and RE, however, the dynamical mechanisms are not well understood. Based on previous Taylor model, we firstly study the effects of external input and self-inhibition of RE on epilepsy transition. We show that increasing external input and self-inhibition of RE can lead the system from epileptic state to normal state, and vice versa. Next, we explore two stimulus strategies added in RE and various transition behaviors can be induced, such as high saturated state to clonic. Meanwhile, as the intensity of stimulation increasing, they can not only suppress the SWD, but also produce tonic-clonic oscillation. Finally, the control of DBS on single neuron cluster and two neuron clusters are compared and we find stimulating RE and TC simultaneously is a superior mode to stimulate anyone of RE or TC. It is hoped that the results we obtained will have an enlightenment on clinical treatment.

Effectiveness, immunogenicity, and safety of influenza vaccines with MF59 adjuvant in healthy people of different age groups: A systematic review and meta-analysis.

BACKGROUND: Influenza is a severe disease burden among all age groups. This study aimed to review the efficacy of inactivated influenza vaccines with MF59 adjuvant and non-adjuvanted inactivated influenza vaccines among all age groups against specific influenza vaccine strains. METHODS: Literature search of PubMed, Embase, Medline, OVID, and Cochrane Library Trials (CENTRAL) was implemented up to March 1, 2019. Homogeneity qualified studies were included forData were extracted such as study country location, demographic characteristics, and measure outcomes, and were analyzed by a random effect model and sensitivity analyses to identify heterogeneity. Risk of bias was evaluated using the Cochrane Risk of Bias Tool. RESULTS: We retrieved 1,021 publications and selected 31 studies for full review, including 17 trials for meta-analysis and 6 trials for qualitative synthesis. MF59-adjuvanted influenza vaccines demonstrated better immunogenicity against specific vaccine virus strains compared to non-adjuvanted influenza vaccine both in healthy adult group (RR = 2.10; 95% CI: 1.28-3.44) and the healthy aged (RR = 1.26; 95% CI: 1.10-1.44). CONCLUSION: The quality of evidence is moderate to high for seroconversion and seroprotection rates of influenza vaccine. MF59-adjuvanted influenza vaccines are superior to non-adjuvanted influenza vaccines to enhance immune responses of vaccination in healthy adults and older adults, and could be considered for routine use especially the monovalent prepandemic influenza vaccines.

Surface-mediated construction of diverse coordination-dominated nanostructures with 4-azidobenzoic acid molecule.

The coordination reactions of 4-Azidobenzoic Acid (ABA) molecules on different active surfaces are studied by scanning tunneling microscopy and density functional theory calculations. ABA molecules deposited on Ag(111)/Ag(100)/Cu(100) held at room temperature lead to the decomposition of azide groups and the release of a N2 molecule per ABA molecule. Two residual segments of ABA molecules can interact with one Ag/Cu adatom to form a coordination dimer through the N-Ag/Cu-N coordination bond on different substrates. Different orientations with different symmetries can result in different nanostructures based on the dimers. Interestingly, the residual segments of ABA molecules can generate four Cu adatoms as the coordination center on Cu(100) to form a novel coordination complex after annealing, which is the first report for trapping four adatoms as a coordination center. The number and the species of adatoms captured can be changed to alter coordination structures. It expounds that various regulatory effects of different substrates lead to the diversity of nanostructures dominated by coordination bonds.