Improved Performance of Air-Processed Perovskite Solar Cells via the Combination of Chlorine Precursors and Potassium Thiocyanate.

Due to their low cost and high efficiency, hybrid perovskite solar cells (PSCs) have shown the most outstanding competitiveness among third-generation photovoltaic (PV) devices. However, several challenges remain unresolved, among which the limited stability is arguably the main. Chlorine (Cl) has been widely employed to yield PV performances, but the Cl-doping mechanism and its role in mixed-halide PSCs are not entirely understood. Here, we investigate the effect of Cl-doping using different precursors such as formamidinium chloride (FACl), cesium chloride (CsCl), and lead chloride (PbCl2), which lead to the incorporation of Cl at different sites of the perovskite crystal. We demonstrate that the stability and efficiency of air-processed PSCs are strongly affected by Cl bonding into the cationic chloride precursor. Furthermore, adding potassium thiocyanate (KSCN) leads to the maximum efficiency of 18.1%, improving the operational stability with only 18% PCE loss after 520 h, stored under ambient conditions. Incorporating CsCl and KSCN presents an effective approach to further boost the performance and thermal stability of PSCs by tailoring the composition of the perovskite's composition. Finally, we used the slot-die method to demonstrate that our strategy is scalable for large-area devices that have shown similar performance. Our results show that fully air-processed and stable PSCs with high efficiency for large production and commercialization are achievable.

Highly Efficient and Ultrasensitive Large-Area Flexible Photodetector Based on Perovskite Nanowires.

Hybrid organic-inorganic perovskites have shown exceptional semiconducting properties and microstructural versatility for inexpensive, solution-processable photovoltaic and optoelectronic devices. In this work, an all-solution-based technique in ambient environment for highly sensitive and high-speed flexible photodetectors using high crystal quality perovskite nanowires grown on Kapton substrate is presented. At 10 V, the optimized photodetector exhibits a responsivity as high as 0.62 A W-1 , a maximum specific detectivity of 7.3 × 1012 cm Hz1/2 W-1 , and a rise time of 227.2 µs. It also shows remarkable photocurrent stability even beyond 5000 bending cycles. Moreover, a deposition of poly(methyl methacrylate) (PMMA) as a protective layer on the perovskite yields significantly better stability under ambient air operation: the PMMA-protected devices are stable for over 30 days. This work demonstrates a cost-effective fabrication technique for high-performance flexible photodetectors and opens opportunities for research advancements in broadband and large-scale flexible perovskite-based optoelectronic devices.

Hysteresis-Free 1D Network Mixed Halide-Perovskite Semitransparent Solar Cells.

The morphology of hybrid organic-inorganic perovskite films is known to strongly affect the performance of perovskite-based solar cells. CH3 NH3 PbI3-x Clx (MAPbI3-x Clx ) films have been previously fabricated with 100% surface coverage in glove boxes. In ambient air, fabrication generally relies on solvent engineering to obtain compact films. In contrast, this work explores the potential of altering the perovskites microstructure for solar cell engineering. This work starts with CH3 NH3 PbI3-x Clx , films with grain morphology carefully controlled by varying the deposition speed during the spin-coating process to fabricate efficient and partially transparent solar cells. Devices produced with a CH3 NH3 PbI3-x Clx film and a compact thick top gold electrode reach a maximum efficiency of 10.2% but display a large photocurrent hysteresis. As it is demonstrated, the introduction of different concentrations of bromide in the precursor solution addresses the hysteresis issues and turns the film morphology into a partially transparent interconnected network of 1D microstructures. This approach leads to semitransparent solar cells with negligible hysteresis and efficiencies up to 7.2%, while allowing average transmission of 17% across the visible spectrum. This work demonstrates that the optimization of the perovskites composition can mitigate the hysteresis effects commonly attributed to the charge trapping within the perovskite film.

Solvent-Antisolvent Ambient Processed Large Grain Size Perovskite Thin Films for High-Performance Solar Cells.

In recent years, hybrid organic-inorganic halide perovskites have been widely studied for the low-cost fabrication of a wide range of optoelectronic devices, including impressive perovskite-based solar cells. Amongst the key factors influencing the performance of these devices, recent efforts have focused on tailoring the granularity and microstructure of the perovskite films. Albeit, a cost-effective technique allowing to carefully control their microstructure in ambient environmental conditions has not been realized. We report on a solvent-antisolvent ambient processed CH3NH3PbI3-xClx based thin films using a simple and robust solvent engineering technique to achieve large grains (>5 µm) having excellent crystalline quality and surface coverage with very low pinhole density. Using optimized treatment (75% chlorobenzene and 25% ethanol), we achieve highly-compact perovskite films with 99.97% surface coverage to produce solar cells with power conversion efficiencies (PCEs) up-to 14.0%. In these planar solar cells, we find that the density and size of the pinholes are the dominant factors that affect their overall performances. This work provides a promising solvent treatment technique in ambient conditions and paves the way for further optimization of large area thin films and high performance perovskite solar cells.

An ultra-broadband perovskite-PbS quantum dot sensitized carbon nanotube photodetector.

Organic-inorganic perovskites have been hailed as promising candidates for optoelectronic and photovoltaic devices, but their operation remains limited to the visible spectrum. Here, we combine single-wall carbon nanotubes, PbS quantum dots and a perovskite to synthesize hybrid devices suitable for operation in both the visible and near-infrared. The photodetectors thus fabricated show responsivities as high as 0.5 A W-1 and 0.35 A W-1 at 500 nm and at 1300 nm, respectively, with an applied bias of 1 V. Moreover, the incorporation of nanotubes within the perovskite matrix facilitates the carrier extraction, resulting in response time under 250 µs, a gain-bandwidth product of 0.1 MHz and detectivities of 1.4 × 1011 Jones and 0.9 × 1011 Jones at 500 nm and at 1300 nm, respectively. This unique approach opens new pathways for the development of low-cost, high-speed and broadband perovskite-based optoelectronic devices for large-scale manufacturing.

[Clinical, epidemiological and therapeutic features of biliary tract cancers: about 20 cases]. / Cancers biliaires: aspects épidémiologiques cliniques et thérapeutiques à propos de 20 cas.

Biliary tract cancers mainly occur in two sites: gallbladder cancer which are adenocarcinomas and intra- and extrahepatic cholangiocarcinomas. We conducted a retrospective study of 20 cases with biliary tract cancer in the Department of Surgery at the General Hospital in Grand-Yoff between January 2006 and October 2014. 40% of patients had gallbladder cancer, 60% of patients had common bile duct cancer. Sex ratio was 1. The average age of patients was 58.1 years. The average time to diagnosis was 3.77 months. Symptomatology was dominated by icteric syndrome and right hypochondrium pain. All patients had biological manifestation of cholestatic syndrome. Abdominal ultrasound was performed in 65% of patients, while abdominal CT scan in 85% of cases and MRI in 35% of cases. Advanced cancers were predominant in our case series (n=19). The majority of patients underwent palliative surgery. The most practiced treatment was biliary diversion (50% of patients). There was a predominance of cholangiocarcinomas. The overall operative morbidity rate was 43.75%. The overall mortality rate in our patients with biliary tract cancers of any site was 31.25%. Median survival was 4 months and a half. Biliary tract cancers have multifaceted features and can be differentiated essentially among intrahepatic cholangiocarcinoma, extrahepatic cholangiocarcinoma, gallbladder adenocarcinoma whose evolution is globally different but the prognosis is spontaneously poor.

Highly Sensitive Switchable Heterojunction Photodiode Based on Epitaxial Bi2FeCrO6 Multiferroic Thin Films.

Perovskite multiferroic oxides are promising materials for the realization of sensitive and switchable photodiodes because of their favorable band gap (<3.0 eV), high absorption coefficient, and tunable internal ferroelectric (FE) polarization. A high-speed switchable photodiode based on multiferroic Bi2FeCrO6 (BFCO)/SrRuO3 (SRO)-layered heterojunction was fabricated by pulsed laser deposition. The heterojunction photodiode exhibits a large ideality factor ( n = ∼5.0) and a response time as fast as 68 ms, thanks to the effective charge carrier transport and collection at the BFCO/SRO interface. The diode can switch direction when the electric polarization is reversed by an external voltage pulse. The time-resolved photoluminescence decay of the device measured at ∼500 nm demonstrates an ultrafast charge transfer (lifetime = ∼6.4 ns) in BFCO/SRO heteroepitaxial structures. The estimated responsivity value at 500 nm and zero bias is 0.38 mA W-1, which is so far the highest reported for any FE thin film photodiode. Our work highlights the huge potential for using multiferroic oxides to fabricate highly sensitive and switchable photodiodes.

High-performance nanotube-enhanced perovskite photodetectors.

Organic-inorganic perovskites have already shown a tremendous potential for low-cost light-harvesting devices. Yet, the relatively low carrier mobilities in bulk perovskites still prevent large-area devices with performances competing with state-of-the-art technologies. Here, we tackle this fundamental challenge by incorporating single-wall carbon nanotubes within a perovskite matrix by means of a simple two-step method in ambient air. Using this nano-engineered hybrid film, we demonstrate large-area photodetectors with responsivities up-to 13.8 A.W-1 and a broad spectral response from 300 to 800 nm, indicating that photocurrent generation arises from the charge transfer from the perovskite matrix to the embedded nanotube network. As the nanotubes facilitate the carrier extraction, these photodetectors also show a fast response time of 10 ms. This is significantly faster than most of previous reports on perovskite-based photodetectors, including devices with much smaller photosensitive areas. This approach is also well-suited for large-scale production of other perovskite-based light-harvesting devices.

[Torsion of wandering spleen in a teenager: about a case]. / Torsion chronique d'une rate baladeuse chez un adolescent: à propos d'un cas.

Wandering or migrating spleen is a rare anomaly which is usually described in children. Complications, which include pedicle torsion, are common and can be life-threatening. We report the case of a 17 year-old patient with a long past medical history of epigastric pain suffering from wandering spleen with chronic torsion of the pedicle. The clinical picture was marked by spontaneously painful epigastric mass, evolved over the past 48 hours. Abdominal ultrasound objectified heterogeneous hypertrophied ectopic spleen in epigastric position and a subcapsular hematoma. Doppler showed a torsion of splenic pedicle which was untwisted 2 turns and a small blood stream on the splenic artery. Abdominal CT scan with contrast injection showed a lack of parenchymal enhancement of large epigastric ectopic spleen and a subcapsular hematoma. The diagnosis of wandering spleen with chronic torsion of the pedicle complicated by necrosis and subcapsular hematoma was confirmed. The patient underwent splenectomy. The postoperative course was uneventful. We here discuss the contribution of ultrasound and CT scan in the diagnosis of wandering spleen with chronic torsion of the pedicle.

[Acute generalized peritonitis due to uterine perforation following abortion: case study observation]. / Péritonite aigue généralisée par perforation utérine post abortum à propos d'une observation.

UNLABELLED: Clandestine abortion is known to be a major contributor to maternal mortality. We report a case of a 25-year old patient in her 12th week of amenorrhea with peritonitis due to uterine perforation following abortion, admitted with abdomen and pelvis pain, vomiting and diarrhea. Clinical examination on admission showed asthenic peritonitis. Surgical exploration showed widespread acute peritonitis secondary to a perforation of the uterine dome, with collection of 1500 cc of purulent material, dilated bowel loops and multiple false membranes. SURGERY: pus aspiration, peritoneal lavage; uterine suture, drainage. The postoperative course was uneventful, the patient was discharged after 15 days.

Multiple exciton generation induced enhancement of the photoresponse of pulsed-laser-ablation synthesized single-wall-carbon-nanotube/PbS-quantum-dots nanohybrids.

The pulsed laser deposition method was used to decorate appropriately single wall carbon nanotubes (SWCNTs) with PbS quantum dots (QDs), leading to the formation of a novel class of SWCNTs/PbS-QDs nanohybrids (NHs), without resorting to any ligand engineering and/or surface functionalization. The number of laser ablation pulses (NLp) was used to control the average size of the PbS-QDs and their coverage on the SWCNTs' surface. Photoconductive (PC) devices fabricated from these SWCNTs/PbS-QDs NHs have shown a significantly enhanced photoresponse, which is found to be PbS-QD size dependent. Wavelength-resolved photocurrent measurements revealed a strong photoconductivity of the NHs in the UV-visible region, which is shown to be due to multiple exciton generation (MEG) in the PbS-QDs. For the 6.5 nm-diameter PbS-QDs (with a bandgap (Eg) = 0.86 eV), the MEG contribution of the NHs based PC devices was shown to lead to a normalized internal quantum efficiency in excess of 300% for photon energies ≥4.5Eg. While the lowest MEG threshold in our NHs based PC devices is found to be of ~2.5Eg, the MEG efficiency reaches values as high as 0.9 ± 0.1.

Purification and sidewall functionalization of multiwalled carbon nanotubes and resulting bioactivity in two macrophage models.

This study examined the consequences of surface carboxylation of multiwalled carbon nanotubes (MWCNT) on bioactivity. Since commercial raw MWCNT contain impurities that may affect their bioactivity, HCl refluxing was exploited to purify raw "as-received" MWCNT by removing the amorphous carbon layer on the MWCNT surface and reducing the metal impurities (e.g. Ni). The removal of amorphous carbon layer was confirmed by Raman spectroscopy and thermogravimetric analysis. Furthermore, the HCl-purified MWCNT provided more available reaction sites, leading to enhanced sidewall functionalization. The sidewall of HCl-purified MWCNT was further functionalized with the -COOH moiety by HNO(3) oxidation. This process resulted in four distinct MWCNT: raw, purified, -COOH-terminated raw MWCNT, and -COOH-terminated purified MWCNT. Freshly isolated alveolar macrophages from C57Bl/6 mice were exposed to these nanomaterials to determine the effects of the surface chemistry on the bioactivity in terms of cell viability and inflammasome activation. Inflammasome activation was confirmed using inhibitors of cathepsin B and Caspase-1. Purification reduced the cell toxicity and inflammasome activation slightly compared to raw MWCNT. In contrast, functionalization of MWCNT with the -COOH group dramatically reduced the cytotoxicity and inflammasome activation. Similar results were seen using THP-1 cells supporting their potential use for high-throughput screening. This study demonstrated that the toxicity and bioactivity of MWCNT were diminished by removal of the Ni contamination and/or addition of -COOH groups to the sidewalls.

Photoelectrocatalytic degradation of chlortetracycline using Ti/TiO2 nanostructured electrodes deposited by means of a Pulsed Laser Deposition process.

Ti/TiO(2) electrode was prepared by means of the Pulsed Laser Deposition method and used in a photoelectrocatalytic oxidation (PECO) process in order to degrade chlortetracycline (CTC). The deposited TiO(2) coatings were found to be of rutile structure. High treatment efficiency of CTC was achieved by the PECO process compared to the conventional electrochemical oxidation, direct photolysis and photocatalysis processes. Several factors such as current intensity, treatment time, UV lamp position and initial concentration of CTC were investigated. Using a 2(4) factorial matrix, the best performance for CTC degradation (74.3% of removal) was obtained at a current intensity of 0.5A during 120 min of treatment time and when the UV lamp was immersed in the solution in the presence of 25 mg L(-1) of CTC. The current intensity and treatment time were the main parameters influencing the degradation rate of CTC. Subsequently, a central composite design methodology has been investigated to determine the optimal experimental parameters for CTC degradation. The PECO process applied under optimal conditions (at current intensity of 0.39 A during 120 min with internal position of the UV lamp) is able to oxidize around 74.2 ± 0.57%, of CTC.