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Experiments operating a Cs D2 line (852.1 nm: 62P3/2→62S1/2) laser, pumped by blue wing absorption of different thermal Cs-rare gas ground state pairs, were analyzed. Using a 10 cm sealed gas cell, the D2 line laser performance is highest for Cs-Ar at 513K, and for Cs-Kr and Cs-Xe at 473 K. Overall, the highest optical-to-optical efficiency measured was 1.1% with a linear slope efficiency of 1.5% for the Cs-Ar collision pair at 513 K. All three Cs-rare gas mixtures show a D2 line laser performance increase with temperature towards a peak efficiency, followed by a decrease as temperature is increased beyond the peak performance point. At lower temperatures ≤453 K the efficiency was highest with Cs-Xe, at 473 K highest with Cs-Kr, whereas at higher temperatures ≥ 493 K the efficiency was highest with Cs-Ar. Measurement of the reduced absorption coefficient for the peak of the blue satellite of the different collision pairs resulted in values of 1.2∙10-36 cm5 for Cs-Ar at 836.7 nm, 2.0∙10-36 cm5 for Cs-Kr at 841.1 nm, and 3.0∙10-36 cm5 for Cs-Xe at 842.7 nm. Simulations of the data using the detailed BLAZE Multiphysics software suite were also performed, which aid in the understanding of the basic physics behind the XPAL system. The simulations indicate that energy pooling significantly inhibits laser performance at higher temperatures above 500 K.

Recent advances in copper chalcogenide-based nanocrystals (NCs), copper sulfide, and copper selenide derived nanostructures, have drawn considerable attention. However, reports of crystal phase and shape engineering of binary or ternary copper telluride NCs remain rare. Here, a colloidal hot-injection approach for producing binary copper/tin telluride, and ternary copper tin telluride NCs with controllable compositions, crystal structures, and morphologies is reported. The crystal phase and growth behavior of these tellurides are systematically studied from both experimental and theoretical perspectives. The morphology of Cu1.29 Te NCs is modified from 1D nanorods with different aspect ratios to 2D nanosheets and 3D nanocubes, by controlling the preferential growth of specific crystalline facets. A controllable phase transition from Cu1.29 Te to Cu1.43 Te NCs is also demonstrated. The latter can be further converted into Cu2 SnTe3 and SnTe through Sn incorporation. Temperature dependent thermoelectric properties of metal (Cu and Sn) telluride nanostructure thin films are also studied, including Cu1.29 Te, Cu1.43 Te, Cu2 SnTe3 , and SnTe. Cu2 SnTe3 is a low carrier density semimetal with compensating electron and hole Fermi surface pockets. The engineering of crystal phase and morphology control of colloidal copper tin telluride NCs opens a path to explore and design new classes of copper telluride-based nanomaterials for thermoelectrics and other applications.

Thermoelectric materials that can generate electricity from waste heat will play an important role in the global sustainable energy solution. Low dimensional materials open new routes to high performance thermoelectric properties due to their unique density of states with confined electrons and holes. Here, we report that the phase engineered two dimensional transition metal dichalcogenides represent a new class of high performance thermoelectric materials. The organolithium chemically exfoliated nanosheets of MoS2 containing a high concentration of metallic 1T phase MoS2 show superior thermoelectric properties, with a room temperature power factor of 73.1 μW m−1 K−2, which is much higher than the pristine graphene or single wall carbon nanotubes can yield. Our first principle calculations on monolayer 1T phase MoS2 provide physical insight of their metallic and hole conductive nature, which happens to be important origins of their advantageous thermoelectric properties. These metallic 1T phase MoS2 nanosheets also reveal interesting moisture sensitive thermoelectric properties, indicating their potential diverse applications not only as thermoelectric energy harvesting devices but also as self-powered gas sensors.

A new spray doping method is presented that allows for easily tunable thermoelectric properties of thin film carbon nanotube (CNT) polymer composites. An airbrush introduces small molecule Polyethyleneimine into existing p-type CNT films converting it to an n-type composite. This technique allows for the conversion of a single p-type film into a multi-section device of alternating p- and n-type segments. A thermoelectric generator (TEG) design is presented with the effort to address current design issues facing thin film thermoelectric devices as a commercially viable TEG. The Seebeck coefficient and electrical conductivity were tested under different dopant concentrations and compared with traditional solution based methods.

Two-dimensional (2D) materials have recently opened a new avenue to flexible thermoelectric materials with enhanced performance because of their unique electronic transport properties. Here, we report a feasible approach to improve the thermoelectric performance of transition-metal dichalcogenides by effectively decorating 2D MoS

Highly robust and flexible n-type thermoelectric (TE) films based on Ag2Te nanoshuttle/polyvinylidene fluoride were prepared by a solution-processable method without a surfactant. A good power performance of over 30 μW (m K2)-1 at room temperature was achieved. Moreover, the synthesized fabrics also exhibited potential for application in flexible electronic devices with negligible performance change after 1000 bending cycles.

A systematic colloidal synthesis approach to prepare tin(II, IV) chalcogenide nanocrystals with controllable valence and morphology is reported, and the preparation of solution-processed nanostructured thermoelectric thin films from them is then demonstrated. Triangular SnS nanoplates with a recently-reported π-cubic structure, SnSe with various shapes (nanostars and both rectangular and hexagonal nanoplates), SnTe nanorods, and previously reported Sn(IV) chalcogenides, are obtained using different combinations of solvents and ligands with an Sn4+ precursor. These unique nanostructures and the lattice defects associated with their Sn-rich composition allow the production of flexible thin films with competitive thermoelectric performance, exhibiting room temperature Seebeck coefficients of 115, 81, and 153 μV K-1 for SnS, SnSe, and SnTe films, respectively. Interestingly, a p-type to n-type transition is observed in SnS and SnSe due to partial anion loss during post-synthesis annealing at 500 °C. A maximum figure of merit (ZT) value of 0.183 is achieved for an SnTe thin film at 500 K, exceeding ZT values from previous reports on SnTe at this temperature. Thus, a general strategy to prepare tin(II) chalcogenide nanocrystals is provided, and their potential for use in high-performance flexible thin film thermoelectric generators is demonstrated.

We report on the fabrication of flexible and freestanding n-type thermoelectric Cu intercalated Bi 2 Se 3 nanoplatelet/Polyvinylidene Fluoride (PVDF) composite films. The optimized power factor and figure of merit (ZT) of the Cu 0.1 Bi 2 Se 3 nanoplatelet/PVDF composites are 103 μW m −1 K −2 and 0.10 at 290 K, respectively, which are one of the highest values for n-type thermoelectric films. The mechanism by which the Seebeck coefficient and electrical conductivity can be partially decoupled is explained in details: PVDF can not only grantee the robust and flexibility but also create a high trap-state by introducing the energy barrier at the organic/inorganic interface, thus a high level of Seebeck coefficient is maintained for the composite system while a remarkable improvement on electrical conductivity was achieved. The thermoelectric films show high mechanical durability with only a 13% decrease in performance after 5000 bending cycles (bending curvature 1/2 mm −1 ). The overall performance of the n-type thermoelectric films approaches the values required for efficient flexible thermoelectric power generators.

Because of the continued development and production of a variety of nanomaterials and nanoparticles, their uptake and effects on the biota of marine ecosystems must be investigated. Filter feeding bivalve molluscs are highly adapted for capturing particles from the external environment and readily internalize nano- and micro-sized particles through endocytosis, so they are commonly used as valuable indicator species for nanoparticle studies. In these studies, adult eastern oysters, Crassostrea virginica, were exposed to a range of titanium dioxide nanoparticle (TiO2-NP) concentrations (5, 50, 500, and 5000 μg/L) in conjunction with natural sunlight. Isolated hepatopancreas tissues were also exposed to the same TiO2-NP concentrations using particles exposed to similar light and dark conditions. Dose-dependent decreases in lysosomal stability were observed in the adult oyster studies as well as in the isolated tissues, at exposures as low as 50 μg/L. Titanium accumulation in isolated hepatopancreas tissue studies was directly correlated to lysosomal destabilization. Based on measurements of lipid peroxidation as an indicator of oxidative stress, TiO2-NPs toxicity was not related to increased ROS production over the short-term course of these exposures. Analysis of particle size using dynamic light scattering (DLS) indicated that concentration had a significant impact on agglomeration rates, and the small agglomerates as well as individual particles are readily processed by oysters. Overall, this study illustrates that low concentrations of TiO2-NPs may cause sublethal toxicity on oysters, which might be enhanced under natural sunlight conditions. In estuarine environments, where these nanomaterials are likely to accumulate, agglomeration rates, interaction with organics, and responses to sunlight are critical in determining the extent of their bioreactivity and biological impacts.

In this work, the application of an aluminum (Al)/multiwall carbon nanotube (MWCNT)/Al, multilayered electrode to flexible, high-efficiency, alternating current driven organic electroluminescent devices (AC-OEL), is reported. The electrode is fabricated by sandwiching a spray-cast nanonetwork film of MWCNTs between two evaporated layers of Al. The resulting composite film facilitates a uniform charge distribution across a robust crack-free electrode under various bending angles. It is demonstrated that these composite electrodes stabilize the power efficiency of flexible devices for bending angles up to 120°, with AC-OEL device power efficiencies of ≈22 lm W−1 at luminances of ≈4000 cd m−2 (using no output coupling). Microscopic examination of the Al/MWCNTs/Al electrode after bending of up to 1300 cycles suggests that the nanotubes significantly enhance the mechanical properties of the thin Al layers while providing a moderate modification to the work function of the metal. While the realization of robust, high-brightness, and high-efficiency AC-OEL devices is potentially important in their future lighting applications, it is anticipated that this to also have significant impact in standard organic light emitting diodes lighting applications.

In this work, a high-performance alternating current (AC) filed-induced chromatic-stable white polymer electroluminescence (WFIPEL) device was fabricated by combining a fluorophor Poly(9,9-dioctylfluorene) (PFO)-based blue device with a yellow down-conversion layer (YAG:Ce). A maximum luminance of this down-conversion FIPEL device achieves 3230 cd m(-2), which is 1.41 times higher than the device without the down-conversion layer. A maximum current efficiency and power efficiency of the down-conversion WFIPEL device reach 19.7 cd A(-1) at 3050 cd m(-2) and 5.37 lm W-1 at 2310 cd m(-2) respectively. To the best of our knowledge, the power efficiency is one of the highest reports for the WFIPEL up to now. Moreover, Commison Internationale de L'Eclairage (CIE) coordinates of (0.28, 0.30) is obtained by adjusting the thickness of the down-conversion layer to 30 mu m and it is kept stable over the entire AC-driven voltage range. We believe that this AC-driven, down-conversion, WFIPEL device may offer an easy way towards future flat and flexible lighting sources. (C) 2015 Elsevier B.V. All rights reserved.

Highly-flexible thermoelectric fabrics were fabricated based on a layered structure, composed of a thin active layer of self-assembled tellurium nanorods and a substrate layer of polyvinylidene fluoride. The resulting thermoelectric fabrics show a high room temperature power factor of 45.8 μW m(-1) K(-2), which opens a new avenue to fabricate highly-flexible sustainable energy sources.

Poly(phenylene), poly(3-hexylthiophene), and poly(fluorene)-based copolymers bearing alternating thiophene (PPT, P3HTT, and PFT) and 5,5-dimethylcyclopentadiene co-repeat units (PPCp, P3HTCp, PFCp) were examined to establish how the identity of the latter manipulates the optical absorption, photoluminescence, thermal properties, (spectro)electrochemistry, and atmospheric stability of these systems. The results of our investigation show that the 4π electron diene moiety reduces the optical band gap of the poly(fluorene) and poly(3-hexylthiophene)-based copolymers when compared against their all-aromatic congeners while having the opposite effect on the poly(phenylene) class. Fluorescence studies reveal that the emission maxima λem of the diene systems are lower in energy among the three copolymer sets, however, quantum yields ΦF are also lower indicating that the diene-moiety compromises photoluminescence. Regarding thermal properties, the identity of the co-repeat unit (i.e. diene vs. thiophene) was found to have a negligible effect on copolymer glass-transition temperature Tg, however, the polyaromatics exhibit higher thermal stability irrespective of copolymer class. Cyclic voltammetry data show that the onset of oxidation (Eonset) decreases in the order of poly(fluorene), poly(phenylene), and poly(3-hexylthiophene) derivatives suggesting that the aromatic co-repeat units play a critical role in establishing the HOMO energy. Moreover, when copolymers within each class are compared, the diene-containing systems always exhibit a lower Eonset indicating that the diene moiety increases the HOMO energy when used in lieu of thiophene. Solution-phase stability studies under ambient atmospheric conditions show the poly(3-hexylthiophene)s to be the most stable class of copolymers followed by the poly(phenylene)s and poly(fluorene)s respectively. In addition to the comparative analyses described herein, three model configurational triads of the poly(3-hexylthiophene) derivative P3HTCp were characterized to allow for the unambiguous assignment of copolymer regiochemistry that was determined to be regiorandom. Finally, a polymer light-emitting diode (PLED) was constructed using PFCp as the emissive layer as a proof-of-principle that diene-containing copolymers can be used as active materials in opto-electronic devices.

The optoelectronic properties of semiconductor nanoparticles (NPs) depend sensitively on their surface ligands. However, introducing certain organic ligands to the solution-synthesized CZTSe NPs unfavorably suppresses the interaction among those NPs. These organic ligands prevent the NPs from dissolving in water and create an insulating barrier for charge transportation, which is the key property for semiconductor devices. In our study, by adopting Na2S to displace the associated organic ligands on Cu2ZnSnSe4 (CZTSe), we obtained high solubility NPs in an environmentally friendly polar solvent as well as excellent charge transport properties. Toxicity of CZTSe: Na2S NPs was determined to be around 10 mg/L. Because of the inorganic ligand S2– around CZTSe NPs, thin films can be easily fabricated by solution processing out of benign solvents like water and ethanol. After annealing, a homogeneous CZTSSe absorbing layer without carbon point defects was obtained. As the S2– effectively facilitates the electron...

A suite of complementary high-throughput screening systems for combinatorial films was developed at National Institute of Standards and Technology to facilitate the search for efficient thermoelectric materials. These custom-designed capabilities include a facility for combinatorial thin film synthesis and a suite of tools for screening the Seebeck coefficient, electrical resistance (electrical resistivity), and thermal effusivity (thermal conductivity) of these films. The Seebeck coefficient and resistance are measured via custom-built automated apparatus at both ambient and high temperatures. Thermal effusivity is measured using a frequency domain thermoreflectance technique. This paper will discuss applications using these tools on representative thermoelectric materials, including combinatorial composition-spread films, conventional films, single crystals, and ribbons.

Highly efficient and stable electrocatalysts, particularly those that are capable of multifunctionality in the same electrolyte, are in high demand for the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR). In this work, highly monodisperse CoP and Co2 P nanocrystals (NCs) are synthesized using a robust solution-phase method. The highly exposed (211) crystal plane and abundant surface phosphide atoms make the CoP NCs efficient catalysts toward ORR and HER, while metal-rich Co2 P NCs show higher OER performance owing to easier formation of plentiful Co2 P@COOH heterojunctions. Density functional theory calculation results indicate that the desorption of OH* from cobalt sites is the rate-limiting step for both CoP and Co2 P in ORR and that the high content of phosphide can lower the reaction barrier. A water electrolyzer constructed with a CoP NC cathode and a Co2 P NC anode can achieve a current density of 10 mA cm-2 at 1.56 V, comparable even to the noble metal-based Pt/C and RuO2 /C pair. Furthermore, the CoP NCs are employed as an air cathode in a primary zinc-air battery, exhibiting a high power density of 62 mW cm-2 and good stability.

Comparing rigid inorganic layer, polymeric semiconducting gate layer exhibits superior flexibility as well as efficient carrier manipulation in high frequency AC cycles. Mechanism of the carrier manipulation at the gate in forward and reversed bias of AC cycle is studied. The flexible PET-based AC-OEL device with poly[(9,9-bis(3'-((N,N-dimethyl)-Nethylammonium)- propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] (PFN-Br) gate shows a stable electroluminescent performance in frequency sweep with a color rendering index (CRI) over 81 at 2800K color temperature.

This article examines the potential of bifunctional nanomaterials for the imaging and treatment of cancer. Several nanomaterials possess properties desirable for a cancer therapy and have been the subject of research as anticancer agents. Those that have received the most attention include encapsulated iron oxides, single- and multiwalled carbon nanotubes, gold nanorods and gold nanoshells. This article first considers thermal ablative therapy incancer, focusing on the mechanisms of thermotoxicity and thermoresistance before discussing a number of nanomaterials with applications for cancer treatment. In particular, it evaluates the use of nanomaterials in thermal therapy. It also looks at gold nanoshells and nanorods, taking into account their physical properties, and concludes with an assessment of iron-oxide nanoparticles and future directions for nanomaterials as multifunctional agents for cancer therapy.

Solution-grown films of CsPbBr

Precise control of the selective growth of heterostructures with specific composition and functionalities is an emerging and extremely challenging topic. Here, the first investigation of the difference in binding energy between a series of metal-semiconductor heterostructures based on layered V

The BLAZE Multiphysics™ software simulation suite was specifically developed to model highly complex multiphysical systems in a computationally efficient and highly scalable manner. These capabilities are of particular use when applied to the complexities associated with high energy laser systems that combine subsonic/transonic/supersonic fluid dynamics, chemically reacting flows, laser electronics, heat transfer, optical physics, and in some cases plasma discharges. In this paper we present detailed cw and pulsed gas laser calculations using the BLAZE model with comparisons to data. Simulations of DPAL, XPAL, ElectricOIL (EOIL), and the optically pumped rare gas laser were found to be in good agreement with experimental data.

Engineered atomic dislocations have been used to create a novel, Sb2 Te3 nanoplate-like architecture that exhibits a unique antisymmetric chirality. High-resolution transmission electron microscopy (HRTEM) coupled with atomic force microscopy and X-ray photoelectron spectroscopy reveals the architectures to be extremely well ordered with little residual strain. Surface modification of these topologically complex macrostructures (≈3 µm) has been achieved by direct growth of metallic Ag nanoparticles onto the edge sites of the Sb2 Te3 . Again, HRTEM shows this nanoparticle decoration to be atomically sharp at the boundaries and regularly spaced along the selvedge of the nanostructure. Transport experiments of densified films of these assemblies exhibit marked increases in carrier density after nanoengineering, yielding 3.5 × 104 S m-1 in electrical conductivity. An increased Seebeck coefficient by 20% in parallel with electrical conductivity is also observed. This gives a thermoelectric power factor of 371 µW m-1 K-2 , which is the highest value for a flexible, freestanding film to date. These results suggest an entirely new direction in the search for wearable power harvesters based on topologically complex, low-dimensional nanoassemblies.

Copper-based chalcogenides that comprise abundant, low-cost, and environmental friendly elements are excellent materials for a number of energy conversion applications, including photovoltaics, photocatalysis, and thermoelectrics (TE). In such applications, the use of solution-processed nanocrystals (NCs) to produce thin films or bulk nanomaterials has associated several potential advantages, such as high material yield and throughput, and composition control with unmatched spatial resolution and cost. Here we report on the production of Cu3SbSe4 (CASe) NCs with tuned amounts of Sn and Bi dopants. After proper ligand removal, as monitored by nuclear magnetic resonance and infrared spectroscopy, these NCs were used to produce dense CASe bulk nanomaterials for solid state TE energy conversion. By adjusting the amount of extrinsic dopants, dimensionless TE figures of merit (ZT) up to 1.26 at 673 K were reached. Such high ZT values are related to an optimized carrier concentration by Sn doping, a minimized lattice thermal conductivity due to efficient phonon scattering at point defects and grain boundaries, and to an increase of the Seebeck coefficient obtained by a modification of the electronic band structure with Bi doping. Nanomaterials were further employed to fabricate ring-shaped TE generators to be coupled to hot pipes, which provided 20 mV and 1 mW per TE element when exposed to a 160 ºC temperature gradient. The simple design and good thermal contact associated with the ring geometry and the potential low cost of the material solution processing may allow the fabrication of TE generators with short payback times.

A solution-processed, all-phosphor, three-color (i.e., blue, green, and red), alternating current-driven white field-induced polymer electroluminescent device (WFIPEL), with low operational voltage, high luminance, high efficiency, high color-rendering index (CRI), and excellent color-stability, was demonstrated. The devices employed poly(vinylidene fluoride–trifluoroethylene–chlorofluoroethylene) [P(VDF–TrFE–CFE)] dielectric modified by single-walled carbon nanotubes (SWNTs) to further improve the dielectric characteristics, as the insulating layer. This significantly lowers the driving voltage of the device. Moreover, hole-generation layer and electron-transporting layer with high conductivity were used to more efficiently form and confine excitons in the emissive layer. The resulting WFIPEL devices show significant improvements in performance as compared to previous reports. Specifically, the devices exhibit a low turn-on voltage of 10 V, a maximum luminance of 7210 cd m −2 , a maximum current efficiency and power efficiency of 33.8 cd A −1 and 10.5 lm W −1 , and a CRI of 82. The power efficiency is even 10 times higher than the highest previous report (1 lm W −1 ).

A semi-closed tubular light-trapping geometry is developed for dye sensitized solar cell to stabilize its power conversion efficiency (PCE) in wide light intensity range. The tubular cell consists of a dye-sensitized porous TiO2 coated and semi-closed glass tube as photoanode, an opaque platinum metal foil wrapped on the outside of photoanode as counter electrode, and electrolyte filling in their interlayer. The open end of photoanode serves as the only light entrance. The experiment, calculation and optical studies demonstrated that the tubular geometry is beneficial to light trapping and absorption, charge transport and heat dissipation, in comparison to a planar counterpart. The PCE of tubular cell can remain about 85% of its original value even if the irradiated light intensity increases from 1 to 5 Sun, in contrast, that of planar counterpart decreases to about 60% of its original value. This feature makes the tubular cell has potential as an effective light collector in low-cost condenser solar cell system.

As the essential building blocks of many electronic devices, solid state thin-films are attracting extensive interest. Soluble nanocrystals (NCs) make it possible to develop robust, low-cost, large-scale fabrication methods for thin-films. However, the organic surface ligands normally used to stabilize the NCs make those thin-films a NC–ligand complex which may possess varied electrical performance compared to a single component system. Previous models could only estimate the charge transportation characteristics in those films quantitatively by considering the capping ligands as a barrier of charges from inter-particle hopping. In this work, we demonstrated that starting from first principles density functional theory, the carrier mobility in a CZTS NC–ligand complex can be determined quantitatively, and guided by this model, we developed a low-cost, low-temperature technique to fabricate CZTS thin films which have a carrier mobility of up to 10.9 cm2/(VS).

The purpose of the work is to investigate whether the electromagnetic properties of multi-walled carbon nanotubes (MWCNT) in the presence of radiofrequency (RF) energy is (1) safe, and (2) improves the precision of the therapeutic efficiency of the RF-ablation (RFA) procedure. An in vitro phantom was created for evaluating temperature near RF treated nanotubes. For the in vivo study, three baboons and six pigs were submitted for RFA procedure in superior/inferior kidney poles embolized with a non-adherent, lipophilic embolic agent (marsembol) with or without MWCNT. Tissue damage in the surrounding kill zone was assayed through caspase-3 activation. The in vitro results showed marked heat increase only in the region of the nanotubes. In vivo, necrosis/ischemic damage resulted from RFA therapy alone, RFA plus marsembol only. In marsembol + MWCNT condition, dramatic disruption of cell membranes and sub-cellular organelles was found whereas the nuclear membranes and basal cell membranes remained largely intact. The marsembol vaporized under RFA and tissue fluid filled the space. This caused the MWCNT to cluster within the new aqueous environment. RFA plus marsembol + MWCNT created a well-defined demarcation between healthy and apoptotic cells as evidenced by a marked reduction of caspase-3 expression. By contrast, there was a much less defined ablation zone in the absence of MWCNT. In conclusion, the combination of RFA plus marsembol + MWCNT embolization delineated the kill zone in vitro and in vivo. We demonstrate that MWCNTs remain in the ablation region thus minimizing their migration to the systemic circulation.

The effect of solution-processed p-type doping of hole-generation layers (HGLs) and electron-transporting layer (ETLs) are systematically investigated on the performance of solution-processable alternating current (AC) field-induced polymer EL (FIPEL) devices in terms of hole-generation capability of HGLs and electron-transporting characteristics of ETLs. A variety of p-type doping conjugated polymers and a series of solution-processed electron-transporting small molecules are employed. It is found that the free hole density in p-type doping HGLs and electron mobility of solution-processed ETLs are directly related to the device performance, and that the hole-transporting characteristics of ETLs also play an important role since holes need to be injected from electrode through ETLs to refill the depleted HGLs in the positive half of the AC cycle. As a result, the best FIPEL device exhibits exceptional performance: a low turn-on voltage of 12 V, a maximum luminance of 20 500 cd m−2, a maximum current and power efficiency of 110.7 cd A−1 and 29.3 lm W−1. To the best of the authors' knowledge, this is the highest report to date among FIPEL devices driven by AC voltage.

We report a simple way of enhancing blue emission in Poly (9,9-dioctylfluorenyl-2,7-diyl) (PFO) based alternating current field driven electroluminescence devices by mixing graphite nano platelets in the emission layer. Significantly strong and well resolved blue peaks at 437 nm and 470 nm are observed both in the devices’ electroluminescence and photoluminescence spectra with the presence of graphite nano platelets. The origin of this strong blue emission has been identified as the PFO’s beta-phase formation confirmed by transmission electron microscopy images and UV–Vis absorption spectra. The nano platelets loading in PFO solution can be controlled by the dispersion time in organic solvents. When the loading increases, the green emission in the electroluminescence spectrum can be reduced. This technique has been found useful in the generation of bright white light when illuminating through down conversion phosphor.

The high-color-quality white emission in an AC-driven field-induced electroluminescence (FIPEL) device consisting of a white emitting ter-polymer: poly(fluorene–benzothiadiazole–quinoline) PF–BT–QL combined with a red emitting dye: Bis(2-methyl-dibenzof,hquinoxaline)(acetylacetonate)iridium (III) Ir(MDQ)2(acac) was achieved. The wide EL emission effectively covered the visible spectral region at the concentration of 5% Ir(MDQ)2(acac) in PF–BT–QL and largely enriched the color rendering capability with a CIE (0.36, 0.38) close to the ideal equal-energy white (0.33, 0.33) and a CRI as high as 97.4, close to the blackbody curve characteristic and CCT between 3034 K and 5334 K which are required for high-quality white-light illumination. When further increasing the concentration of Ir(MDQ)2(acac) to 10%, leading to a more pure white with CIE (0.36, 0.37) and a CRI as high as 97.1. Surprisingly, the FIPEL devices containing 20% and 30% Ir(MDQ)2(acac) in PF–BT–QL still exhibit high-quality white emission with CIE (0.42, 0.37) and (0.32, 0.38) and CRI 93.9 and 88.9 at high electric field, respectively. To the best of our knowledge, there are no reports of two-component FIPELs with a CRI > 90, especially with such a high concentration of the phosphor dopant. We attribute this to the unique carrier injection characteristics of the AC-driven field induced device. This further suggests its great potential application in display and solid state lighting.

The thermoelectric properties of large diameter multiwalled carbon nanotubes synthesized by chemical vapor deposition have been measured after successively longer periods of high energy probe sonication. Electrical conductivity decreases with increased sonication time due to shortening of the nanotubes. The initial Seebeck coefficient before sonication is −2.5 μV/K, but increases to 12 μV/K for sonication periods longer than 12 h. This effect is attributed to the introduction of defects and shortening of the nanotubes during sonication which exposes previously shielded carbon from internal walls to oxygen doping from exposure to atmosphere which results in increased p-type doping and a positive thermoelectric power. Temperature dependent measurements indicate that this oxygen doping of the exposed nanotube ends has a thermally activated charge transfer energy since low temperature thermoelectric power measurements of the sonicated samples approach that of the raw n-type nanotubes.

Organic thin-film electroluminescent (EL) devices, such as organic light-emitting diodes (OLEDs), typically operate using constant voltage or direct current (DC) power sources. Such approaches require power converters (introducing power losses) and make devices sensitive to dimensional variations that lead to run away currents at imperfections. Devices driven by time-dependent voltages or alternating current (AC) may offer an alternative to standard OLED technologies. However, very little is known about how this might translate into overall performance of such devices. Here, a solution-processed route to creating highly efficient AC field-induced polymer EL (FIPEL) devices is demonstrated. Such solution-processed FIPEL devices show maximum luminance, current efficiency, and power efficiency of 3000 cd m−2, 15.8 cd A−1, and 3.1 lm W−1 for blue emission, 13 800 cd m−2, 76.4 cd A−1, and 17.1 lm W−1 for green emission, and 1600 cd m−2, 8.8 cd A−1, and 1.8 lm W−1 for orange-red emission. The high luminance and efficiency, and solution process pave the way to industrial roll-to-roll manufacturing of solid state lighting and display.

Acid treatment of carbon nanotubes is a post synthesis processing step used to clean carbon nanotubes. We show that exposure of the nanotubes to oxygen rich reagents including nitric and sulfuric acid results in an increase of the thermoelectric power. Improving dispersion through the use of the surfactant triton-x results in a further increase in TEP of up to 21%. Additionally, refluxing in an oxygen rich acidic solution results in improved dispersion and an increased TEP. These results indicate that improved dispersion of the nanotubes by either sonication or reflux leads to increased oxygenation and thermopower.

An evaluation of methods is represented to extract parameters from the current–voltage ( I – V ) characteristics of solar cells. This evaluation includes five aspects: applicability, convergence, stability, calculation speed, and error on various types of I – V data. Six current popular extraction methods are discussed and evaluated in this work. We find that the widely adopted method using the reciprocals of slope at two points is the fastest and simplest approach to estimating resistances, but it is an incomplete method to obtain the other parameters. Of the five complete methods, the Ishibashi–Kimura method shows the best accuracy (4.5% average error) while having bad applicability. Generally speaking, the Lambert W-function method is the best comprehensive method with good accuracy, applicability, and convergence, though the calculation speed is relatively lower than the other four methods.

Freestanding few layer graphene platelet/polyvinylidene fluoride composites have been synthesized, resulting in flexible, light weight, and durable electrically conducting films. These composites exhibit reasonable thermoelectric properties including a maximum electrical conductivity of 2005 S m−1, Seebeck coefficient of 18.3 μV K−1, and power factor of 0.52 μW m−1 K−2. The temperature dependent behavior of these properties is also investigated. The electrical conductivity of the composites exhibits thermal fluctuation-assisted tunneling behavior coupled with a high energy phonon scattering term, while the thermoelectric power is characterized by electron-phonon enhanced metallic diffusion thermopower plus a phonon drag term. This results in a characteristic change in majority charge carrier type from hole to electron as the temperature decreases below 60 K. These composites have the potential to be used in low power applications where sufficient waste heat is available.

Synthesis of poly(2-hexylthieno[3,4-b]thiophene-co-4,8-didodecyloxybenzo[1,2-b:4, 5-b′]dithiophene) (PTB) is presented using a simple and low cost method. Anhydrous DMF and toluene was added into the mixture of 4,6-dibromo-2-hexylthieno[3,4-b] thiophene,2,6-Bis(trimethyltin)-4,8-didodecyloxybenzo[1,2-b:4,5-b′]dithiophene and Pd(PPh3)4. The polymerization was carried out at 120°C for 12 h. The PTB product was precipitated in methanol and dried in vacuum. The HOMO and LUMO energies of the polymer were calculated using Density Functional Theory (DFT) calculations to be compared with the experimental results.