Metal halide perovskites are an emerging class of solution processable materials that have exhibited remarkable optoelectronic properties, such as high carrier mobility 1 , long diffusion length 2,3 , bandgap tunability 4,5 , high luminescence efficiency 6 and narrow emission bandwidth 7 . These properties, along with the ease of preparation of halide perovskite materials, have led to great advances in applications such as solar cells [8][9][10][11] , photodetectors 12,13 and light-emitting diodes (LEDs) [14][15][16][17] . The development of perovskite LEDs (PeLEDs) has, in particular, been rapid: in 2014 we reported electroluminescence (EL) from halide perovskites 14 and by 2018 we and others had achieved external quantum efficiencies of >20% 18-21 .

Reducing environmental impact is a key challenge for perovskite optoelectronics, as most high-performance devices are based on potentially toxic lead-halide perovskites. For photovoltaic solar cells, tin-lead (Sn–Pb) perovskite materials provide a promising solution for reducing toxicity. However, Sn–Pb perovskites typically exhibit low luminescence efficiencies, and are not ideal for light-emitting applications. Here we demonstrate highly luminescent germanium-lead (Ge–Pb) perovskite films with photoluminescence quantum efficiencies (PLQEs) of up to ~71%, showing a considerable relative improvement of ~34% over similarly prepared Ge-free, Pb-based perovskite films. In our initial demonstration of Ge–Pb perovskite LEDs, we achieve external quantum efficiencies (EQEs) of up to ~13.1% at high brightness (~1900 cd m−2), a step forward for reduced-toxicity perovskite LEDs. Our findings offer a new solution for developing eco-friendly light-emitting technologies based on perovskite semiconductors.

Metal halide perovskites (MHPs) are a promising class of materials for next‐generation display and lighting applications. Since the first demonstration of bright electroluminescence (EL) from perovskite light‐emitting diodes (PeLEDs) in 2014, the EQEs of these devices increased from below 1% to more than 20% in merely four years. Despite the meteoritic rise of device efficiencies that placed the new LED technology in the spotlight, many scientific and technical challenges remain, preventing PeLEDs from advancing further into practical applications. The success of inorganic III‐V LEDs, or commercial LED technologies in general, lies in the ability to demonstrate the reliable generation of blue EL. For PeLEDs, high operational stability and efficient blue EL remain to be some of the most pressing goals. To accelerate further developments in these areas, the recent progress in the research of PeLEDs is reviewed. The authors attempt to establish preliminary connections between the degradation mechanisms and the strategies for improvements, exemplified by a selection of recent representative works in the field. Lessons learned from organic LEDs and perovskite solar cells point toward some of the most important directions. This progress report serves as a catalyst for further interdisciplinary research involving materials scientists, chemists, and physicists working together to realize operationally stable PeLEDs.

The power conversion efficiency (PCE) of low-bandgap mixed Pb−Sn perovskite solar cells (PSCs) has been significantly hindered by large open-circuit voltage (V oc ) loss and poor fill factor (FF). Herein, mixed Pb−Sn perovskite films with a composition (FASnI 3 ) 0.6 (MAPbI 3 ) 0.4 were processed with a simple delayed annealing (DA) treatment that enables perovskite films with significantly reduced surface roughness. The treatment reduces nonradiative recombination of interfacial contacts when t h e p e r o v s k i t e fi l m s a r e i n t e r f a c e d w i t h p o l y ( 3 , 4ethylenedioxythiphene):poly(styrenesulfonate) (PEDOT:PSS) and fullerene (C 60 ). Charge transfer at the carrier-collection interfaces has been effectively improved, in agreement with time-resolved photoluminescence (TRPL) and transient photovoltage/photocurrent results. Consequently, the champion cell based on perovskite films with DA treatment shows a high V oc of 0.824 V, indicating a greatly suppressed V oc loss (for a bandgap of ∼1.25 eV), and an overall PCE of over 18.6%.

Ethylene biosynthesis and the ethylene signaling pathway regulate plant salt tolerance by activating the expression of downstream target genes such as those related to ROS and Na+/K+ homeostasis. The Salt Overly Sensitive (SOS) pathway regulates Na+/K+ homeostasis in Arabidopsis under salt stress. However, the connection between these two pathways is unclear. Through genetic screening, we identified two sos2 alleles as salt sensitive mutants in the ein3-1 background. Neither Ethylene-Insensitive 2 (EIN2) nor EIN3 changed the expression patterns of SOS genes including SOS1, SOS2, SOS3 and SOS3-like Calcium Binding Protein 8 (SCaBP8), but SOS2 activated the expression of one target gene of EIN3, Ethylene and Salt-inducible ERF 1 (ESE1). Moreover, Ser/Thr protein kinase SOS2 phosphorylated EIN3 in vitro mainly at the S325 site and weakly at the S35, T42 and S606 sites. EIN3 S325A mutation reduced its transcriptional activating activity on ESE1 promoter:GUS in a transient GUS assay, and impaired its ability to rescue ein3-1 salt hypersensitivity. Furthermore, SOS2 activated salt-responsive ESE1 target gene expression under salt stress. Therefore, EIN3-SOS2 might link the ethylene signaling pathway and the SOS pathway in Arabidopsis salt responses.

Double perovskite La2NiMnO6 is an attractive spintronic material with magnetocapacitance and magnetoresistance effects. These outstanding properties are associated with the biphasic characteristic and anti-site defects. To study the biphasic nature of La2NiMnO6, the spontaneous shear strains, crystal structures, microstructures, element distribution, and magnetic properties were investigated. The first principles density functional theory calculations within the Perdew-Burke-Ernzerhof functional were first used to calculate the static formation enthalpies and crystal structures of La2NiMnO6 at different hydrostatic pressures. The coexistence is most likely related to static formation enthalpies and/or spontaneous strains and partly due to the inhomogeneous characteristics of the sample.

All-inorganic cesium lead bromide demonstrates better thermal and chemical stability compared to its hybrid counterparts, and thus it can provide a base for high stability and performance of CsPbBr3-based perovskite light emitting diodes (PeLEDs).

Intracerebral hemorrhage is the most dangerous complication in tPA thrombolytic therapy for ischemic stroke, which occurs as a consequence of endothelial cell death at the blood–brain barrier (BBB) during thrombolytic reperfusion. We have previously shown that cerebral ischemia‐induced rapid occludin degradation and BBB disruption. Here we demonstrated an important role of occludin degradation in facilitating the evolution of ischemic endothelial cells toward death. Cultured brain microvascular endothelial cells (bEnd.3 cells) were exposed to oxygen‐glucose deprivation (OGD) or incubated with occludin siRNA or occludin AAV to achieve an occludin deficiency or over‐expression status before exposing to reoxygenation (R) or TNF‐α treatment. Cell death was assessed by measuring lactate dehydrogenase release, TUNEL staining, and flow cytometry analysis. Inhibition of OGD‐induced occludin degradation with SB‐3CT or over‐expression of occludin with occludin AAV both significantly attenuated OGD/R‐induced apoptosis and pyroptosis in bEnd.3 cells. Consistently, knockdown of occludin with siRNA potentiated TNF‐α‐induced apoptosis, supporting an important role of occludin integrity in endothelial cell survival. Similar results were observed for pyroptosis, in which occludin knockdown with siRNA led to a significant augmentation of cytokines secretion, inflammasome activation, and pyroptosis occurrence in TNF‐α‐treated bEnd.3 cells. Lastly, up‐regulation of c‐Yes, PI3K/AKT, and ERK concurrently occurred with occludin degradation after OGD/R or TNF‐α treatment, and the level of these proteins were further increased when inhibition of occludin degradation or over‐expression of occludin. These data indicate that occludin degradation inflicted during ischemia makes BBB endothelial cells more vulnerable to reperfusion‐associated stress stimuli.