1,720,975 research outputs found
Overcoming Challenges in OLED Technology for Lighting Solutions
No full textIn academic research, OLEDs have exhibited rapid evolution thanks to the development of innovative materials, new device architectures, and optimized fabrication methods, achieving high performance in recent years. The numerous advantages that increasingly distinguish them from traditional light sources, such as a large and customizable emission area, color tunability, flexibility, and transparency, have positioned them as a promising candidate for various applications in the lighting market, including the residential, automotive, industrial, and agricultural sectors. However, despite these promising attributes, the widespread industrial production of OLEDs encounters significant challenges. Key considerations center around efficiency and lifetime. In the present review, after introducing the theoretical basis of OLEDs and summarizing the main performance developments in the industrial field, three crucial aspects enabling OLEDs to establish a competitive advantage in terms of performance and versatility are critically discussed: the quality and stability of the emitted light, with a specific focus on white light and its tunability; the transparency of both electrodes for the development of fully transparent and integrable devices; and the uniformity of emission over a large area
Electron beam curing technology for very high-throughput manufacturing of flexible alternating current powder electroluminescent devices
No full textThick-film alternating current powder-based electroluminescent (ACPEL) succeeds on the market as mature technology for large-area light sources. An additional boost for its development may come from the radiation curing technology. Since it is totally compatible with high-speed roll-to-roll processing, radiation curing can offer multiple advantages to further lower costs and make easier the fabrication process of ACPEL devices. In this paper, the application of the electron beam (EB) curing technology to produce flexible ACPEL devices was explored for the first time. In particular, devices with emitting layer made by EB irradiation were successfully fabricated on poly(ethylene terephthalate) (PET) substrate. Device properties were evaluated and compared with those obtained using the conventional ultraviolet curing process. Smaller driving voltages and higher luminous output were observed for the EB treated samples as a consequence of a more cross-linked polymeric binder of the emitting layer generated. In addition, possible effects of EB overdose were also investigated; experiments revealed that excessively high doses can induce the degradation of both polymeric binder and emitting particles. Therefore, the feasibility of using the EB curing was proven to fabricate ACPEL devices, launching it as the next future technology for more sustainable, very fast, and one-step manufacturing of powder-based alternating current EL devices
New Strategies to Improve the Efficiency of Curcumin-Based Iridium Complexes for OLED Devices
No full textAmong the solid-state lighting technologies, OLEDs occupy a prominent position for the high efficiencies associated with the low CO2 emissions. In line with the recent studies aimed at designing sustainable and biodegradable devices, herein we report on the synthesis of a series of iridium(III) complexes featuring, as β-diketone ligands, curcumin and 6-dehydrogingerdione, two natural compounds found in the rhizome of Curcuma longa and Zingiber officinale. To improve the solubility of both the ligands and prevent the aggregation of the complexes, oleoyl residues were inserted on the phenolic −OH groups. The resulting complexes exhibited a green emission with quantum yields as high as 2.8 % (relative to fluorescein). OLED devices were fabricated by using, as emitting layer, a host-guest blend of the iridium complex in 4,4’-bis(N-carbazolyl)-1,1’-biphenyl (CBP). The morphological analysis revealed that thin films of the emitting layer were homogeneous. The devices fabricated with iridium complexes from 6-dehydrogingerdione exhibited higher luminance, efficiency and power efficiency with respect to the corresponding devices obtained from curcumin; also the functionalization of the β-diketone unit with the oleoyl residue proved to increase significantly the performance of the device. Overall, these data suggest that aggregation is a key factor that compromise the performances of the corresponding OLEDs
Influence of hole transporting material on the improved performance of OLEDs by the surface treatments of ITO layer
No full textITO sputtering study for transparent OLED top electrode
No full textOrganic Light Emitting Diodes (OLEDs) are a cutting-edge lighting technology that allows to create thin, light weight, diffuse-emitting, glare-free, and even transparent light sources having low power consumption, wide color gamut, fast response time, and precise dimming. Transparent OLEDs (TrOLEDs) can be integrated into architectural glass windows, car windshields, divider panels, or lamps, thus enabling the creation of lighting objects with captivating and innovative designs, allowing natural light to pass through, since they are optically transparent when turned off. In order to achieve high-performance TrOLED, it is necessary to develop transparent electrodes with superior optical and electrical properties, to replace the opaque metal top electrodes that are commonly used in bottom-emitting OLEDs. Transparent conducting oxides (TCOs) are the most widely used transparent materials for bottom electrodes, and sputtering technology is the most common technique to deposit such materials. However, sputtering of high-quality TCO is not well suited for the fabrication of OLED top electrodes because it exposes the underlying organic layers to damages by the plasma emission of high-energy particles. In this study, the effects of sputter deposition of Indium Tin Oxide (ITO) on Tris(8-hydroxyquinoline)aluminum(III) (Alq3) OLED active layer have been investigated, to establish the best compromise between process conditions and ITO films electro-optical properties to reduce the damage induced by sputtering. Moreover, the impact of introducing a thin thermally evaporated calcium (Ca) layer, before ITO sputtering, has also been examined. In this case, Ca acts both as a protective layer for the underlying Alq3 and, at the same time, as a good electron injector for OLEDs
Quantitative assessment of dimensional evolution of solitary osteoma of the mandible through 14 years of radiographic follow-up analysis: A unique case report
Full text linkHead & Neck Osteomas are extremely rare osteogenic benign tumors, with unclear pathogenesis and heterogeneous clinical behavior. There are no studies in literature showing the characteristics of dimensional growth of such lesions. We report a case of a peripheral solitary osteoma of the sigmoid notch of the mandibular ramus, describing its radiographic growth in fourteen years. Measurements from OPTs (2003–6x7mm, 2008–8x12mm, 2014–17 × 24mm, 2016–19 × 25mm and 2017–21 × 28mm) and 3d cone-beam computed tomography scan (2016–19 × 15 × 21mm, 2017–21,4 × 19,2 × 22,7) were obtained. The growth of the lesion measured on OPTs was in mean 1.1 × 1.5 mm per year. This is the first case report in literature quantitatively assessing the growth of a solitary osteoma of the mandible through radiographic imaging, which seems to be more than 1 mm per dimension per year
Surgical oncology of the head and neck district during COVID-19 pandemic
Full text linkPurpose: A new member of the Coronaviridae family caused a worldwide pandemic emergency called Coronavirus disease 2019 (COVID-19). Health care workers who come into contact with the upper aero-digestive tract during diagnostic and therapeutic procedures, such as otolaryngologists, oral and maxillofacial surgeons, and head and neck surgeons, may undergo profound changes in their activities and are particularly at risk. We analysed the impact of COVID-19 on our oncological surgical activity. Methods: To address the emergency and guarantee safety of patients referred to our Unit, reproducible guidelines were followed. Surgical activity data during COVID-19 were compared to previous years (2018 and 2019). Results: From 21st February to 25th of May 113 surgical procedures were performed. The average of the two selected years (2018–2019) is 84.5, showing an increase of 34.5% of our activities (statistically significant, p = 0.0011). No patient showed perioperative or postoperative contagion. Conclusion: Due to the conversion of regular Hospitals into COVID Centers, Cancer Centers may encounter an increased demand for procedures. Following strict guidelines, it seems possible to face surgical activity on cancer patients and respect standard procedures aimed at containing the spread of COVID-19 infection
A Comparative Evaluation of Sustainable Binders for Environmentally Friendly Carbon-Based Supercapacitors
Full text linkEnvironmentally friendly energy storage devices have been fabricated by using functional materials obtained from completely renewable resources. Gelatin, chitosan, casein, guar gum and carboxymethyl cellulose have been investigated as sustainable and low-cost binders within the electrode active material of water-processable symmetric carbon-based supercapacitors. Such binders are selected from natural-derived materials and industrial by-products to obtain economic and environmental benefits. The electrochemical properties of the devices based on the different binders are compared by using cyclic voltammetry, galvanostatic charge/discharge curves and impedance spectroscopy. The fabricated supercapacitors exhibit series resistance lower than a few ohms and values of the specific capacitance ranged between 30 F/g and 80 F/g. The most performant device can deliver ca. 3.6 Wh/kg of energy at a high power density of 3925 W/kg. Gelatin, casein and carboxymethyl cellulose-based devices have shown device stability up to 1000 cycles. Detailed analysis on the charge storage mechanisms (e.g., involving faradaic and non-faradaic processes) at the electrode/electrolyte interface reveals a pseudocapacitance behavior within the supercapacitors. A clear correlation between the electrochemical performances (e.g., cycle stability, capacitance retention, series resistance value, coulombic efficiency) ageing phenomena and charge storage mechanisms within the porous carbon-based electrode have been discussed
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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