Push-pull photochromic dyes for semi-transparent solar cells with light-adjustable optical properties and high color-rendering index.

We report the design, synthesis and characterization of push-pull photochromic naphthopyran dyes, incorporating different carbazole moieties as the electron-donor group for use in dye-sensitized solar cells. Compared to a reference dye incorporating a diphenylamine-type donor moiety, the introduction of functionalized carbazoles allows for a hypsochromic shift of the absorption of the coloured isomers of the dyes in the visible region and a better tuning of their spectra to the photopic response of the human eye. Under illumination, the molecules exhibit a broad absorption with a maximum comprised between 546 nm and 571 nm in solution and they reveal relatively fast discoloration kinetics. By using these dyes to fabricate photochromic solar cells whose optical and photovoltaic properties vary with the light exposure, we have achieved a PCE of up to 3% in opaque cells. Using these molecules in semi-transparent solar cells with different electrolytes, a PCE of 2.3% was achieved. We also produced a semi-transparent mini-module with an average visible transmittance varying between 66% and 50% and a colour rendering index around 95 in both the uncoloured and coloured states.

Star-shape non-fullerene acceptor featuring an aza-triangulene core for organic solar cells.

We present the simple synthesis of a star-shape non-fullerene acceptor (NFA) for application in organic solar cells. This NFA possesses a D(A)3 structure in which the electron-donating core is an aza-triangulene unit and we report the first crystal structure for a star shape NFA based on this motive. We fully characterized this molecule's optoelectronic properties in solution and thin films, investigating its photovoltaic properties when blended with PTB7-Th as the electron donor component. We demonstrate that the aza-triangulene core leads to a strong absorption in the visible range with an absorption edge going from 700 nm in solution to above 850 nm in the solid state. The transport properties of the pristine molecule were investigated in field effect transistors (OFETs) and in blends with PTB7-Th following a Space-Charge-Limited Current (SCLC) protocol. We found that the mobility of electrons measured in films deposited from o-xylene and chlorobenzene are quite similar (up to 2.70 × 10-4 cm2 V-1 s-1) and that the values are not significantly modified by thermal annealing. The new NFA combined with PTB7-Th in the active layer of inverted solar cells leads to a power conversion efficiency of around 6.3% (active area 0.16 cm2) when processed from non-chlorinated solvents without thermal annealing. Thanks to impedance spectroscopy measurements performed on the solar cells, we show that the charge collection efficiency of the devices is limited by the transport properties rather than by recombination kinetics. Finally, we investigated the stability of this new NFA in various conditions and show that the star-shape molecule is more resistant against photolysis in the presence and absence of oxygen than ITIC.

Influence of Redox Couple on the Performance of ZnO Dye Solar Cells and Minimodules with Benzothiadiazole-Based Photosensitizers.

ZnO-based dye-sensitized solar cells exhibit lower efficiencies than TiO2-based systems despite advantageous charge transport dynamics and versatility in terms of synthesis methods, which can be primarily ascribed to compatibility issues of ZnO with the dyes and the redox couples originally optimized for TiO2. We evaluate the performance of solar cells based on ZnO nanomaterial prepared by microwave-assisted solvothermal synthesis, using three fully organic benzothiadiazole-based dyes YKP-88, YKP-137, and MG-207, and alternative electrolyte solutions with the I-/I3 -, Co(bpy)3 2+/3+, and Cu(dmp)2 1+/2+ redox couples. The best cell performance is achieved for the dye-redox couple combination YKP-88 and Co(bpy)3 2+/3+, reaching an average efficiency of 4.7% and 5.0% for the best cell, compared to 3.7% and 3.9% for the I-/I3 - couple with the same dye. Electrical impedance spectroscopy highlights the influence of dye and redox couple chemistry on the balance of recombination and regeneration kinetics. Combined with the effects of the interaction of the redox couple with the ZnO surface, these aspects are shown to determine the solar cell performance. Minimodules based on the best systems in both parallel and series configurations reach 1.5% efficiency for an area of 23.8 cm2.

Non-Fullerene Acceptors with an Extended π-Conjugated Core: Third Components in Ternary Blends for High-Efficiency, Post-Treatment-Free Organic Solar Cells.

The synthesis of four non-fullerene acceptors (NFAs) with a "A-π-D-π-A" structure, in which the electron-donating core is extended, was achieved. The molecules differed by the nature of the solubilizing groups on the π-spacer and/or the presence of fluorine atoms on the peripheral electron-accepting units. The optoelectronic properties of the molecules were characterized in solution, in thin film, and in photovoltaic devices. The nature of the solubilizing groups had a minor influence on the optoelectronic properties but affected the organization in the solid state. On the other hand, the fluorine atoms influenced the optoelectronics properties and increased the photo-stability of the molecules in thin films. Compared to reference ITIC, the extended molecules showed a wider absorption across the visible range and higher lowest unoccupied molecular orbital energy levels. The photovoltaic performances of the four NFAs were assessed in binary blends using PM6 (PBDB-T-2F) as the donating polymer and in ternary blends with ITIC-4F. Solar cells (active area 0.27 cm2 ) showed power conversion efficiencies of up to 11.1 % when ternary blends were processed from non-halogenated solvents, without any thermal post-treatment or use of halogenated additives, making this process compatible with industrial requirements.

Photochromic dye-sensitized solar cells with light-driven adjustable optical transmission and power conversion efficiency.

Semi-transparent photovoltaics only allows for the fabrication of solar cells with an optical transmission that is fixed during their manufacturing resulting in a trade-off between transparency and efficiency. For the integration of semi-transparent devices in building, ideally solar cells should generate electricity while offering the comfort for users to self-adjust their light transmission with the intensity of the daylight. Here we report a photochromic dye-sensitized solar cell (DSSC) based on donor-π-conjugated bridge-acceptor structures where the π-conjugated bridge is substituted for a diphenyl-naphthopyran photochromic unit. DSSCs show change in colour and self-adjustable light transmittance when irradiated with visible light and a power conversion efficiency up to 4.17%. The colouration-decolouration process is reversible and these DSSCs are stable over 50 days. We also report semi-transparent photo-chromo-voltaic mini-modules (23 cm2) exhibiting a maximum power output of 32.5 mW after colouration.

S-Shaped Conformation of the Quaterthiophene Molecular Backbone in Two-Dimensional Bisterpyridine-Derivative Self-Assembled Nanoarchitecture.

The conformation and the two-dimensional self-assembly of 4'-(3',4″-dihexyloxy-5,2':5',2″:5″,2‴-quaterthien-2,5‴-diyl)-bis(2,2':6',2″-terpyridine) molecules are theoretically and experimentally investigated. This molecular building block forms a hydrogen-bonded chiral supramolecular nanoarchitecture on graphite at the solid/liquid interface. Scanning tunneling microscopy (STM) shows that the molecule adopts an S-shaped conformation in this structure. DFTB+ calculations reveal that this conformation is not the lowest-energy conformation. The molecular nanoarchitecture appears to be stabilized by hydrogen bonding as well as van der Waals interactions. I-, L-, and D-shaped molecular conformations are, however, locally observed at the domain boundary, but these conformations do not self-assemble into organized 2D structures.

Evaluation of PICC complications in orthopedic inpatients with bone infection for long-term intravenous antibiotics therapy.

PURPOSE: The purpose of this study is to evaluate the complications of peripherally inserted central catheters (PICCs) in orthopedic patients with chronic bone orthopedic infection. MATERIALS AND METHODS: The institutional review board approved this retrospective study and informed consent was waived. Records of 180 consecutives PICCs placed in patients hospitalized in the orthopedic surgery department were reviewed. All patients had bones infections necessitating a long-term intravenous antibiotics therapy. All PICC complications were recorded during the patient hospitalization: infection [catheter-related bloodstream infection (CRBSI), central line associated bloodstream infection (CLABSI), exit-site infection, septic phlebitis], thrombosis, occlusion, mechanical complication (accidental withdrawal, malposition, median nerve irritation). RESULTS: One hundred and eighty PICCs were placed in 136 patients. Mean duration of catheterization was 21 days (total 3911 PICC-days). Thirty-six PICCs (20%) were removed due to complications (9.2 complications per 1000 PICC-days): 14 (8%) infections (one CRBSI (Pseudomonas aeruginosa), one septic phlebitis (P. aeruginosa), two exit-site infections and 10 CLABSIs), 11 (6%) occlusions, and 12 (7%) mechanical complications (10 accidental withdrawals, one malposition, one median nerve irritation). One patient had two complications simultaneously. After multivariate analysis, two risk factors were significantly associated with the overall occurrence of complications: age more than 70 years [OR = 2.89 (1.06-7.89], p = 0.04] and number of lumen at least two [OR = 2.64 (1.03-6.75), p = 0.04]. CONCLUSIONS: Even in orthopedic patients with chronic orthopedic bone infection, PICCs have a low rate of complication. The increasing lumen number of the PICC is a potential risk factor in our series.

Electrodeposited ZnO nanowires as photoelectrodes in solid-state organic dye-sensitized solar cells.

A new approach for developing solid-state dye-sensitised solar cells (DSSCs) on glass/ITO and plastic substrates (PEN/ITO) is presented in this manuscript. A two step electrodeposition technique has been employed to realize the ZnO photoelectrodes. First a ZnO thin film is deposited on the ITO substrate and subsequently on this buffer layer 650 nm long ZnO nanowires are grown. The different nanostructured electrodes are crystallized and show a transparency close to 80% in the visible spectral range. The electrodes are then sensitized with a new purely organic dye, whose synthesis is presented here, which reveals a wide absorption spectrum and a high molar extinction coefficient. Finally, the sensitized electrodes were employed for the fabrication of liquid and solid-state DSSCs, using, respectively, a liquid iodine/iodide electrolyte and the spiro-OMeTAD hole transporter. These devices represent the first solid-state DSSCs fabricated using electrodeposited zinc oxide nanowires. Their power conversion efficiency is still limited, respectively, 0.18% and 0.03% under standard AM 1.5G sunlight (100 mW cm(-2)), nevertheless, these results prove the interest in this low-temperature deposition method for the realization of nanostructured electrodes on rigid and flexible substrates, and open up new perspectives for the development of solid state DSSCs on plastic substrates.

Incidence of pulmonary cement embolism after real-time CT fluoroscopy-guided vertebroplasty.

PURPOSE: To prospectively evaluate the incidence of pulmonary cement embolism (PCE) after vertebroplasty in procedures performed under real-time computed tomographic (CT) fluoroscopy guidance. MATERIALS AND METHODS: A total of 85 vertebroplasties were performed in 51 consecutive patients (31 women, 20 men; mean age, 71.9 y; range, 48-92 y) in 51 sessions. The needle was inserted with guidance from intermittent single-shot CT scans, and intermittent CT fluoroscopy was used during cement injection only. To reduce the risk of extravertebral or extraosseous leakage, several procedures (cement injection stopping/slowing, needle position changes) were employed. The chest and treated bone were scanned immediately after vertebroplasty. These CT images included the entire thorax as well as the treated vertebrae. RESULTS: No cement emboli were observed on CT after vertebroplasty. After 85 vertebroplasty procedures, 44 extravertebral leaks were detected. Epidural leaks were observed on CT in six treated vertebrae (7%), in 12 cases in the anterior external venous plexus (14.1%), in five in the azygos vein (5.8%), in 19 in the disc space (22%), and in two in the foraminal space (2.3%). On a per-patient basis, the odds of leaks increased with the number of vertebroplasties (P = .05) and the volume of cement used (P = .0412). There was also a higher probability of leak (P < .05) for osteoporotic vertebral compression fractures (67.9%; 95% confidence interval, 47.7%-84.1%) than osteolytic spinal metastases (34.8%; 16.4%-57.3%). CONCLUSIONS: PCE did not occur after vertebroplasty under CT fluoroscopy guidance. Further larger prospective vertebroplasty studies are needed to compare the rates of PCE for CT versus conventional fluoroscopic guidance.