Blending Self-Assembled Monolayers for Enhanced Band Alignment and Improved Morphology in p-i-n Perovskite Photodetectors.

Perovskite photodetectors, devices that convert light to electricity, require good extraction and low noise levels to maximize the signal-to-noise ratio. Self-assembling monolayers (SAMs) have been shown to be effective hole transport materials thanks to their atomic layer thickness, transparency, and energetic alignment with the valence band of the perovskite. While efforts are being made to reduce noise levels via the active layer, little has been done to reduce noise via SAM interfacial engineering. Herein, we report hybrid perovskite photodetectors with high detectivity by blending two different SAMs (2-PACz and Me-4PACz). We find that with a 1:1 2-PACz:Me-4PACz ratio (by weight), the devices achieved a low noise of 1 × 10-13 A Hz-1/2, a high responsivity of 0.41 A W-1 at 710 nm, and a specific detectivity of 6.4 × 1011 Jones at 710 nm at -0.5 V, outperforming its two counterparts. In addition to the improved noise levels in these devices, impedance spectroscopy revealed that higher recombination lifetimes of 0.85 µs were achieved for the 1:1 2-PACz:Me-4PACz-based photodetectors, confirming their low defect density.

Enhancing Circularly Polarized Electroluminescence through Energy Transfer within a Chiral Polymer Host.

Organic light-emitting diodes (OLEDs) that are able to emit high levels of circularly polarized (CP) light hold significant promise in numerous future technologies. Such devices require chiral emissive materials to enable CP electroluminescence. However, the vast majority of current OLED emitter classes, including the state-of-the-art triplet-harvesting Thermally Activated Delayed Fluorescence (TADF) materials, produce very low levels of CP electroluminescence. Here we showcase a host-guest strategy that allows for energy transfer between a chiral polymer host and a representative chiral TADF emitter. Such a mechanism results in large amplification of the circular polarization of the emitter. As such, this study presents a promising avenue to further boost the performance of CP-OLED devices, enabling their further development and eventual commercialization. This article is protected by copyright. All rights reserved.

Dark Current in Broadband Perovskite-Organic Heterojunction Photodetectors Controlled by Interfacial Energy Band Offset.

Lead halide perovskite and organic semiconductors are promising classes of materials for photodetector (PD) applications. State-of-the-art perovskite PDs have performance metrics exceeding silicon PDs in the visible. While organic semiconductors offer bandgap tunability due to their chemical design with detection extended into the near-infrared (NIR), perovskites are limited to the visible band and the first fraction of the NIR spectrum. In this work, perovskite-organic heterojunction (POH) PDs with absorption up to 950 nm are designed by the dual contribution of perovskite and the donor:acceptor bulk-heterojunction (BHJ), without any intermediate layer. The effect of the energetics of the donor materials is systematically studied on the dark current (Jd) of the device by using the PBDB-T polymer family. Combining the experimental results with drift-diffusion simulations, it is shown that Jd in POH devices is limited by thermal generation via deep trap states in the BHJ. Thus, the best performance is obtained for the PM7-based POH, which delivers an ultra-low noise current of 2 × 10-14 A Hz-1/2 and high specific detectivity of 4.7 × 1012 Jones in the NIR. Last, the application of the PM7-based POH devices as NIR pulse oximeter with high-accuracy heartbeat monitoring at long-distance of 2 meters is demonstrated.

A Conjugated Carboranyl Main Chain Polymer with Aggregation-Induced Emission in the Near-Infrared.

Materials exhibiting aggregation-induced emission (AIE) are both highly emissive in the solid state and prompt a strongly red-shifted emission and should therefore pose as good candidates toward emerging near-infrared (NIR) applications of organic semiconductors (OSCs). Despite this, very few AIE materials have been reported with significant emissivity past 700 nm. In this work, we elucidate the potential of ortho-carborane as an AIE-active component in the design of NIR-emitting OSCs. By incorporating ortho-carborane in the backbone of a conjugated polymer, a remarkable solid-state photoluminescence quantum yield of 13.4% is achieved, with a photoluminescence maximum of 734 nm. In contrast, the corresponding para and meta isomers exhibited aggregation-caused quenching. The materials are demonstrated for electronic applications through the fabrication of nondoped polymer light-emitting diodes. Devices employing the ortho isomer achieved nearly pure NIR emission, with 86% of emission at wavelengths longer than 700 nm and an electroluminescence maximum at 761 nm, producing a significant light output of 1.37 W sr-1 m-2.

Rational Design of New Conjugated Polymers with Main Chain Chirality for Efficient Optoelectronic Devices: Carbo[6]Helicene and Indacenodithiophene Copolymers as Model Compounds.

The unique properties of conjugated polymers (CPs) in various optoelectronic applications are mainly attributed to their different self-assembly processes and superstructures. Various methods are utilized to tune and control CP structure and properties with less attention paid to the use of chirality. CPs with main chain chirality are rare and their microscopic and macroscopic properties are still unknown. In this work, the first experimental results are provided along these lines by synthesizing a series of racemic and enantiopure CPs containing statistical and alternating carbo[6]helicene and indacenodithiophene moieties and evaluating their microscopic (optical, energy levels) and macroscopic properties (hole mobilities, photovoltaic performance). It is demonstrated that a small statistical insertion of either the racemic or enantiopure helicene into the polymer backbone finely tunes the microscopic and macroscopic properties as a function of the statistical content. The microscopic properties of the enantiopure versus the racemic polymers with the same helicene loading remain similar. On the contrary, the macroscopic properties, and more interestingly those between the two enantiomeric forms, are altered as a function of the statistical content. Once incorporated into a solar cell device, these chiral CPs display better performance in their enantiopure versus racemic forms.

Fast Near-Infrared Photodetectors Based on Nontoxic and Solution-Processable AgBiS2.

Solution-processable near-infrared (NIR) photodetectors are urgently needed for a wide range of next-generation electronics, including sensors, optical communications and bioimaging. However, it is rare to find photodetectors with >300 kHz cut-off frequencies, especially in the NIR region, and many of the emerging inorganic materials explored are comprised of toxic elements, such as lead. Herein, solution-processed AgBiS2 photodetectors with high cut-off frequencies under both white light (>1 MHz) and NIR (approaching 500 kHz) illumination are developed. These high cut-off frequencies are due to the short transit distances of charge-carriers in the ultrathin photoactive layer of AgBiS2 photodetectors, which arise from the strong light absorption of this material, such that film thicknesses well below 120 nm are sufficient to absorb >65% of NIR to visible light. It is also revealed that ion migration plays a critical role in the photo-response speed of these devices, and its detrimental effects can be mitigated by finely tuning the thickness of the photoactive layer, which is important for achieving low dark current densities as well. These outstanding characteristics enable the realization of air-stable, real-time heartbeat sensors based on NIR AgBiS2 photodetectors, which strongly motivates their future integration in high-throughput systems.

A polymer library enables the rapid identification of a highly scalable and efficient donor material for organic solar cells.

The dramatic improvement of the PCE (power conversion efficiency) of organic photovoltaic devices in the past few years has been driven by the development of new polymer donor materials and non-fullerene acceptors (NFAs). In the design of such materials synthetic scalability is often not considered, and hence complicated synthetic protocols are typical for high-performing materials. Here we report an approach to readily introduce a variety of solubilizing groups into a benzo[c][1,2,5]thiadiazole acceptor comonomer. This allowed for the ready preparation of a library of eleven donor polymers of varying side chains and comonomers, which facilitated a rapid screening of properties and photovoltaic device performance. Donor FO6-T emerged as the optimal material, exhibiting good solubility in chlorinated and non-chlorinated solvents and achieving 15.4% PCE with L8BO as the acceptor (15.2% with Y6) and good device stability. FO6-T was readily prepared on the gram scale, and synthetic complexity (SC) analysis highlighted FO6-T as an attractive donor polymer for potential large scale applications.

Biorenewable Solvents for High-Performance Organic Solar Cells.

With the advent of nonfullerene acceptors (NFAs), organic photovoltaic (OPV) devices are now achieving high enough power conversion efficiencies (PCEs) for commercialization. However, these high performances rely on active layers processed from petroleum-based and toxic solvents, which are undesirable for mass manufacturing. Here, we demonstrate the use of biorenewable 2-methyltetrahydrofuran (2MeTHF) and cyclopentyl methyl ether (CPME) solvents to process donor: NFA-based OPVs with no additional additives in the active layer. Furthermore, to reduce the overall carbon footprint of the manufacturing cycle of the OPVs, we use polymeric donors that require a few synthetic steps for their synthesis, namely, PTQ10 and FO6-T, which are blended with the Y-series NFA Y12. High performance was achieved using 2MeTHF as the processing solvent, reaching PCEs of 14.5% and 11.4% for PTQ10:Y12 and FO6-T:Y12 blends, respectively. This work demonstrates the potential of using biorenewable solvents without additives for the processing of OPV active layers, opening the door to large-scale and green manufacturing of organic solar cells.

Mesenteric revascularisation in a young patient with antiphospholipid syndrome and fibromuscular dysplasia: report of a case and review of the literature.

Fibromuscular dysplasia or fibromuscular hyperplasia is a rare non-atherosclerotic and non-inflammatory vascular disease that primarily involves medium-size and small arteries, most commonly the renal and carotid arteries, and less frequently the vertebral, iliac, subclavian or visceral arteries (mesenteric, hepatic, splenic). Antiphospholipid syndrome is one of the most commonly acquired hypercoagulable states, defined by the association of laboratory evidence of anti-phospholipid antibodies with arterial or venous thrombosis or recurrent pregnancy losses. The presence of these antibodies is associated with an increased risk of thromboembolic phenomena, including peripheral thrombophlebitis, pulmonary thromboembolism, stroke, retinal artery occlusion, myocardial infarction, placental thrombosis and Budd-Chiari syndrome. In this report we discuss the uncommon case of a young male patient with both antiphospholipid syndrome and fibromuscular dysplasia that came to our attention for pulmonary embolism and "angina abdominis" due to occlusion of three mesenteric vessels. The possible relationship between antiphospholipid syndrome and fibromuscular dysplasia encountered in our patient still remains unclear. We treated the patient as if he had the two different diseases. After partial failure of endovascular surgery, the patient underwent surgery with reimplantation of three visceral arteries to the aorta. Subsequently he was treated with stent placement after development of a re-stenosis of one of the three reimplanted visceral arteries. The patient was treated conservatively for antiphospholipid syndrome with anticoagulant oral therapy for life.

ERG conductance expression modulates the excitability of ventral horn GABAergic interneurons that control rhythmic oscillations in the developing mouse spinal cord.

During antenatal development, the operation and maturation of mammalian spinal networks strongly depend on the activity of ventral horn GABAergic interneurons that mediate excitation first and inhibition later. Although the functional consequence of GABA actions may depend on maturational processes in target neurons, it is also likely that evolving changes in GABAergic transmission require fine-tuning in GABA release, probably via certain intrinsic mechanisms regulating GABAergic neuron excitability at different embryonic stages. Nevertheless, it has not been possible, to date, to identify certain ionic conductances upregulated or downregulated before birth in such cells. By using an experimental model with either mouse organotypic spinal cultures or isolated spinal cord preparations, the present study examined the role of the ERG current (I(K(ERG))), a potassium conductance expressed by developing, GABA-immunoreactive spinal neurons. In organotypic cultures, only ventral interneurons with fast adaptation and GABA immunoreactivity, and only after 1 week in culture, were transformed into high-frequency bursters by E4031, a selective inhibitor of I(K(ERG)) that also prolonged and made more regular spontaneous bursts. In the isolated spinal cord in which GABA immunoreactivity and m-erg mRNA were colocalized in interneurons, ventral root rhythms evoked by NMDA plus 5-hydroxytryptamine were stabilized and synchronized by E4031. All of these effects were lost after 2 weeks in culture or before birth in coincidence with decreased m-erg expression. These data suggest that, during an early stage of spinal cord development, the excitability of GABAergic ventral interneurons important for circuit maturation depended, at least in part, on the function of I(K(ERG)).

Endovascular repair of intrathoracic left subclavian artery aneurysm with stent grafts: report of a case and review of the literature.

At present, the standard management of subclavian artery aneurysms is surgical repair. Endovascular treatment of these aneurysms with implantation of a covered stent graft is a relatively new technique that appears to be both feasible and safe. We present the case of a large true aneurysm of the left intrathoracic subclavian artery that was successfully treated with two stent grafts on March 2001. A one-year follow-up CT scan revealed a type 1 secondary endoleak that was successfully treated with a third stent graft. The patient was closely monitored with CT scans that 32 months later confirmed both the patency of the graft and the complete exclusion of the aneurysm, which had decreased in size. At this moment, this is the only case reported in the literature with such a long follow-up but further long-term clinical results will be necessary to fully define the effectiveness of this technique.

Interneurone bursts are spontaneously associated with muscle contractions only during early phases of mouse spinal network development: a study in organotypic cultures.

For a short time during development immature circuits in the spinal cord and other parts of the central nervous system spontaneously generate synchronous patterns of rhythmic activity. In the case of the spinal cord, it is still unclear how strongly synchronized bursts generated by interneurones are associated with motoneurone firing and whether the progressive decline in spontaneous bursting during circuit maturation proceeds in parallel for motoneurone and interneurone networks. We used organotypic cocultures of spinal cord and skeletal muscle in order to investigate the ontogenic evolution of endogenous spinal network activity associated with the generation of coordinate muscle fibre contractions. A combination of multiunit electrophysiological recordings, videomicroscopy and optical flow computation allowed us to measure the correlation between interneurone firing and motoneurone outputs after 1, 2 and 3 weeks of in vitro development. We found that, in spinal organotypic slices, there is a developmental switch of spontaneous activity from stable bursting to random patterns after the first week in culture. Conversely, bursting recorded in the presence of strychnine and bicuculline became increasingly regular with time in vitro. The time course of spontaneous activity maturation in organotypic slices is similar to that previously reported for the spinal cord developing in utero. We also demonstrated that spontaneous bursts of interneurone action potentials strongly correlate with muscular contractions only during the first week in vitro and that this is due to the activation of motoneurones via AMPA-type glutamate receptors. These results indicate the occurrence in vitro of motor network development regulating bursting inputs from interneurones to motoneurones.

Intraparenchymal renal artery aneurysms. Case report with review and update of the literature.

Increased interest in aneurysms involving the renal artery and its branches has occurred during the past 3 decades. The prevalence of renal artery aneurysms is approximately 0.01%-1% in the general population as well as 2.5% in hypertensive patients undergoing angiography. Intraparenchymal renal artery aneurysms (IPRAAs) are rare since being detected in less than 10% of patients with renal artery aneurysms. The Authors report an unusual case of multiple small intrarenal artery aneurysms associated with a large IPRAA located in the mid portion of the right kidney. Usually, IPRAAs are secondary to diseases or injuries of the kidney vascular network. They are classified as true, false, saccular, fusiform, dissecting, and microaneurysms. Potential complications of IPRAAs include peripheral dissection, thrombosis, hypertension, renal infarction and rupture. IRAAs may be detected incidentally as well as present with urologic symptoms and signs related to complications. Actually, IRAAs are investigated by non invasive modalities including duplex ultrasound, magnetic resonance angiography, spiral three-dimensional computed tomography angiography, and three-dimensional reconstructed rotational digital substraction angiography of the segmental and distant branches of the renal artery. Angiography with intrarterial injection of contrast material is the gold standard in diagnosing IPRAAs. Treatment options for IPRAAs include observation, aneurysmectomy with surgical repair, endovascular procedures, nephrectomy or partial nephrectomy. Observation is indicated for asymptomatic intraparenchymal renal artery aneurysms measuring less than 2 cm in diameter. Surgical repair of IPRAAs includes aneurysmectomy and reconstruction of the renal artery by in vivo or ex vivo technique. The procedure is indicated for IPRAAs causing renovascular hypertension, dissection, urologic symptoms, embolization, local expansion and women of childbearing age with a potential for pregnancy. In recent years, transcatheter arterial embolization has emerged as a simple, useful and effective technique in managing IRAAs. The procedure is performed by transfemoral catheterization as well as by superselective catheterization and embolization of interlobar arteries with 3F microcatheters. Endovascular occlusion is obtained by using gelatin sponge, steel coils, detachable baloons, and conventional non-detachable microcoils delivered through a microcatheter. Nephrectomy or partial nephrectomy are reserved for conditions precluding renal revascularization which include overt RAA rupture, covert RAA rupture, artery-to-vein fistula, renal cell carcinoma, end stage nephropaty, renal infarction, severe ischemic renal atrophy or complex intrarenal aneurysms. Recently, partial nephrectomy by the laparoscopic approach has been proposed for managing IPRAAs and the procedure is considered feasible and safe.