Search

AZABODIPY with thiophene and phenyl substituents allows electroluminescence in pure NIR to be achieved.

Chiral lanthanide complexes can be prepared by choosing the achiral antenna ligand and the chiral inducer independently. With this modular approach, complexes optimized for use in efficient CP-OLEDs may be obtained.

Cells exposed to stress factors experience time-dependent variations of metabolite concentration, acting as reliable sensors of the effective concentration of drugs in solution. NMR can detect and quantify changes in metabolite concentration, thus providing an indirect estimate of drug concentration. The quantification of bactericidal molecules released from antimicrobial-treated biomedical materials is crucial to determine their biocompatibility and the potential onset of drug resistance.Real-time NMR measurements of extracellular metabolites produced by bacteria grown in the presence of known concentrations of an antibacterial molecule (irgasan) are employed to quantify the bactericidal molecule released from antimicrobial-treated biomedical devices. Viability tests assess their activity against E. coli and S. aureus planktonic and sessile cells. AFM and contact angle measurements assisted in the determination of the mechanism of antibacterial action.NMR-derived concentration kinetics of metabolites produced by bacteria grown in contact with functionalized materials allows for indirectly evaluating the effective concentration of toxic substances released from the device, lowering the detection limit to the nanomolar range. NMR, AFM and contact angle measurements support a surface-killing mechanism of action against bacteria.The NMR based approach provides a reliable tool to estimate bactericidal molecule release from antimicrobial materials.The novelty of the proposed NMR-based strategy is that it i) exploits bacteria as sensors of the presence of bactericidal molecules in solution; ii) is independent of the chemo-physical properties of the analyte; iii) establishes the detection limit to nanomolar concentrations.

Colloidal semiconductor nanocrystals (NCs) and, recently, nanoplatelets (NPLs), owing to their efficient and narrow-band luminescence, are considered as frontier materials for light-emitting diode (LED) technology. NC-LEDs typically incorporate interfacial layers as charge regulators to ensure charge balancing and high performance. In this Letter, we show the prolongation of the lifetime of multilayer solution-processed NC-LEDs by combining a self-doped conductive conjugated polyelectrolyte and exfoliated molybdenum disulfide (MoS2) flakes as an alternative to PEDOT:PSS. The ink features a neutral pH and a tunable hydrophobicity that mainly results in a remarkable stability of LEDs, using CdSe/CdZnS NPLs.

Nowadays, the use of biodegradable and bio-derived plastics such as poly(lactic acid) (PLA) and cellulose in food packaging applications are replacing the use of different and more conventional oil-derived polymers that are much more expensive and unsuitable for the environment. However, their high transparency to ultraviolet (UV) radiation limits their current commercialization. Therefore, this study focuses on the deposition of organic thin films on commercial PLA and cellulose in order to enhance their performance, in particular for UV shielding. Coatings with different natural and biocompatible (edible) molecules, quinine and p-Coumaric acid, dispersed in different matrices are deposited by comparing different deposition techniques such as spray coating and spin coating. Morphological characterizations are carried out with atomic force microscopy (AFM) and scanning electron microscopy (SEM), with spectroscopic characterizations performed by light transmission measurements. Our results show that it is possible to enhance the UV protection of packaging using a suitable deposition with these biocompatible materials.

Luminescent solar concentrators (LSCs) have been extensively studied as they offer a practical solution to increase the efficiency of silicon-based photovoltaics (PVs). In this context, the use of natural and organic luminescent materials is desirable in order to obtain sustainable and environmentally friendly devices. Moreover, solution-processable organic host–guest systems based on Foerster Resonant Energy Transfer (FRET) processes offer the possibility to exploit a low-cost technique to obtain an efficient energy downshift from the UV–visible to red or deep red emissions in order to concentrate the radiation in the area of maximum efficiency of the PV device. Nevertheless, organic materials are subjected to photodegradation that reduces their optical properties when exposed to UV light and oxygen. In this work, we incorporated two different antioxidant molecules (i.e., octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (Octa) and L-ascorbic acid (L-Asc)) in a three-dye host–guest system and studied the corresponding optical properties after prolonged irradiation times in air. It was found that the presence of the antioxidants, especially L-Asc, slowed the system’s photodegradation down whilst at the same time retaining high emission efficiencies and without interfering with the cascade Resonant Energy Transfer processes among the dyes inserted in the nanochannels of the host.

This review presents an overview of the use of organic functionalized carbon nanostructures (CNSs) in solar energy conversion schemes. Our attention was focused in particular on the contribution of organic chemistry to the development of new hybrid materials that find application in dye-sensitized solar cells (DSSCs), organic photovoltaics (OPVs), and perovskite solar cells (PSCs), as well as in photocatalytic fuel production, focusing in particular on the most recent literature. The request for new materials able to accompany the green energy transition that are abundant, low-cost, low-toxicity, and made from renewable sources has further increased the interest in CNSs that meet all these requirements. The inclusion of an organic molecule, thanks to both covalent and non-covalent interactions, in a CNS leads to the development of a completely new hybrid material able of combining and improving the properties of both starting materials. In addition to the numerical data, which unequivocally state the positive effect of the new hybrid material, we hope that these examples can inspire further research in the field of photoactive materials from an organic point of view.

The rapid appearance of organic optoelectronics as a promising alternative to conventional optoelectronics has been largely achieved through the design and development of new conjugated systems. Th...

Polar semiconducting polymers based on a conjugated polymer backbone endowed with chemically anchored polar groups on the side chains have proved to be particularly interesting as optimization layer at organic/cathode interface in optoelectronic devices. In particular, the pendant phosphonate groups impart water-alcohol solubility allowing easy solution processing, and improve electron injection thanks to both a favorable interfacial dipole of phosphonate groups and an intense coordination interaction between the phosphonate groups and Al cathode. In this work we synthesize alternating fluorene-benzothiadiazole copolymers by proposing a post-polymerization reaction to insert the phosphonate groups. Thanks to this approach it is possible to use standard Suzuki coupling conditions, simplifying the process of synthesis, purification and characterization. The polymer Poly[9,9-bis(6′-diethoxylphosphorylhexyl)-alt-benzothiadiazole] (P2), is tested in conventional organic solar cells as cathode interfacial layers showing, with respect to the control device, an increasing of all the photovoltaic parameters, with a final power conversion efficiency that reaches 5.35% starting from 4.6%. The same trend is observed for multilayered polymer light-emitting diodes with an external quantum efficiency of the P2-based PLED enhanced of 1.5 times with respect to the basic devices with bare Al cathode, and negligible roll-off efficiency. The synergic effects of energy gap modulation and of polar phosphonated pendant functionalities of P2 are compared with the corresponding fluorene-based polar homopolymer. Our results show that, not only a proper selection of side functionalities, but also the tailoring of the energy gap of cathode interfacial materials (CIMs) is a possible effective strategy to engineer cathode of different optoelectronic devices and enhance their performance.

Colloidal semiconductor nanoplatelets (NPLs) are a subgroup of quantum confined materials that have recently emerged as promising active materials for solution processed light-emitting diodes (LEDs) thanks to their peculiar structural and electronic properties as well as their reduced dimensionality. Nowadays, the conventional structure for NPL-based LEDs makes use of poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) as a hole transporting layer (HTL). This is a well-known conjugated conductive polymer because it leads to high LED efficiency, though it has limited stability in air due to its intrinsic acidity and hygroscopicity. Here, we develop a nanocomposite aqueous ink, obtained by blending commercial PEDOT:PSS with water-based, stable and highly concentrated molybdenum disulfide (MoS2) nanosheets, obtained via liquid phase exfoliation (LPE), which is suitable as a HTL for solution processed NPL-based LEDs. We demonstrate that the MoS2 additive effectively works as a performance booster in unpackaged devices, thereby prolonging the lifetime up to 1000 hours under ambient conditions. Moreover, the addition of MoS2 induces a modification of the anode interface properties, including a change in the work function and a significant enhancement of the permittivity of the HTL.

Conjugated polymers with ionic pendant groups (CPEs) are receiving increasing attention as solution-processed interfacial materials for organic solar cells (OSCs). Various anionic CPEs have been successfully used, on top of ITO (Indium Tin Oxide) electrodes, as solution-processed anode interlayers (AILs) for conventional devices with direct geometry. However, the development of CPE AILs for OSC devices with inverted geometry is an important topic that still needs to be addressed. Here, we have designed three anionic CPEs bearing alkyl-potassium-sulfonate side chains. Their functional behavior as anode interlayers has been investigated in P3HT:PC61BM (poly(3-hexylthiophene): [6,6]-phenyl C61 butyric acid methyl ester) devices with an inverted geometry, using a hole collecting silver electrode evaporated on top. Our results reveal that to obtain effective anode modification, the CPEs’ conjugated backbone has to be tailored to grant self-doping and to have a good energy-level match with the photoactive layer. Furthermore, the sulfonate moieties not only ensure the solubility in polar orthogonal solvents, induce self-doping via a right choice of the conjugated backbone, but also play a role in the gaining of hole selectivity of the top silver electrode.

Conjugated polyelectrolytes (CPEs) are defined by a backbone that contains a ?-conjugated electronic structure with pendant ionic functionalities, which make the polymer soluble in water and in polar solvents1. CPEs combine the optical and charge transport properties of organic semiconductors with the possibility of modulating physical properties by electrostatic interactions. Furthermore, the solubility in water and in polar solvents makes CPEs appealing materials both as optical reporters in bio-sensors and bio-imaging applications and as charge regulating layers in organic solar cells2, organic light-emitting diodes and organic thin-films transistors. Recently, the CPE poly[2,6-(4,4-bis-potassium butanylsulfonate-4H-cyclopenta-[2.1-b;3,4-b']dithiophene)-alt-4,7-(2,1,3-benzothiazole)] (PCPDTBT-2SO3K or CPE-2K) has become object of interest because is soluble in water and become doped in presence of a proton source3. In fact, it has been reported that the dopant is H+ and that the addition of sodium hydroxide to CPE-2K solutions reverses the process and de-dopes the polymer. The proposed "doping" mechanism consists in an initial double protonation of the polymer backbone, followed by comproportionation with a non-protonated chain, ultimately leading both to the formation of polarons (radical cations), which are stabilized by the pendant sulphonate groups4. Starting from these considerations, here we present a deep study of the di-alkylated CPE-2K in comparison with mono-alkylated CPE-K (Scheme 1). Through combined spectroscopic (UV-vis-NIR) and electrochemical (cyclic voltammetry) analyses we aim to look into the doping mechanism trying to show how protons cause the organization of both polymers in aggregates, which then stabilize the polarons. A comparison with other CPE systems is also performed.

The 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY)-based molecules have emerged as interesting material for optoelectronic applications. The facile structural modification of BODIPY core provides an opportunity to fine-tune its photophysical and optoelectronic properties thanks to the presence of eight reactive sites which allows for the developing of a large number of functionalized derivatives for various applications. This review will focus on BODIPY application as solid-state active material in solar cells and in photonic devices. It has been divided into two sections dedicated to the two different applications. This review provides a concise and precise description of the experimental results, their interpretation as well as the conclusions that can be drawn. The main current research outcomes are summarized to guide the readers towards the full exploitation of the use of this material in optoelectronic applications.

In the last years, interfacial engineering has played a critical role in promoting the performance of optoelectronic devices as organic solar cells (OSC) and organic light-emitting diodes (OLEDs) since interfacial layers help to form an ohmic contact between the electrodes and the active layers, which is of great importance for charge collection/injection. Conjugated polyelectrolytes (CPEs), which are conjugated polymers bearing side-chain ionic functionalities such as anionic, cationic, or zwitterionic groups, have emerged as a new class of interfacial materials in thin film-based electronic devices thanks to their ability to reduce the barrier between electrode and active layer. In view of this, we designed and synthesized two novel low bandgap anionic copolymers with different anionic pendant groups and different conjugated backbones to obtain hole-transporting layer (HTL) materials as an alternative to commonly used poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate). The functional behavior of these copolymers as anode modifiers is herein preliminarily investigated in an OLED prototype.

Organic light-emitting transistors (OLETs) show the fascinating combination of electrical switching characteristics and light generation capability. However, to ensure an effective device operation, an efficient injection of charges into the emissive layer is required. The introduction of solution-processed conjugated polyelectrolyte (CPE) films at the emissive layer/electrode interface represents a promising strategy to improve the electron injection process by dipole formation. However, their use in optoelectronic devices also involves some limitations because of the ionic nature of CPEs. In this context, neutral conjugated polar polymers (CPPs) represent a valid alternative to CPEs because the conjugated backbones of CPPs are functionalized with polar nonionic side groups, thus avoiding ion-dependent drawbacks. By introducing a layer of polyfluorene-containing phosphonate groups underneath the metal electrodes, we here demonstrate a substantial improvement of the electron injection properties into the OLET-emissive layer and, accordingly, a more than 2-fold increased light power and a 5 times higher external quantum efficiency of p-type OLETs in comparison with reference devices without any interlayer. The great benefit of using a transparent glass substrate allowed to selectively investigate the morphological and photoluminescent characteristics of both CPE- and CPP-buried interlayers within complete OLETs by means of an optical scanning probe technique. This, together with a thorough optoelectronic characterization of the figures of merit of working light-emitting devices, allowed to disclose the origin of the improved optical performance of CPP-based devices as well as the operation mechanisms of the investigated interlayer in the corresponding OLETs.

This article provides insight into the interaction of synthetic conjugated polymers [polyfluorene derivatives (PFDs)] with layers of two-dimensional titanium carbide (Ti3C2Tx). Three derivatives with nonpolar, polar, and charged nitrogen-containing functionalities were synthesized via the Suzuki polycondensation reaction. The organic-inorganic PFD/Ti3C2Tx hybrids were prepared and characterized using X-ray diffraction and a range of microscopic and spectroscopic techniques to elucidate the host guest interaction mechanism. We show that polar polymers with charged nitrogen containing ends'have the strongest interaction with the Ti3C2Tx layers, yielding an increase in interlayer spacing and large shifts in spectroscopic peaks. Furthermore, the effect of polymer backbone juxtaposition between Ti3C2Tx layers on pseudocapacitance is discussed in detail. Our results suggest that new organic materials capable of intercalation between the layers of Ti3C2Tx and other MXeries may be used in the design of hybrid structures for highperformance energy storage applications and beyond.

Hybrid interfaces between living cells and nano/microstructured scaffolds have huge application potential in biotechnology, spanning from regenerative medicine and stem cell therapies to localized drug delivery and from biosensing and tissue engineering to neural computing. However, 3D architectures based on semiconducting polymers, endowed with responsivity to visible light, have never been considered. Here, we apply for the first time a push-coating technique to realize high aspect ratio polymeric pillars, based on polythiophene, showing optimal biocompatibility and allowing for the realization of soft, 3D cell cultures of both primary neurons and cell line models. HEK-293 cells cultured on top of polymer pillars display a remarkable change in the cell morphology and a sizable enhancement of the membrane capacitance due to the cell membrane thinning in correspondence to the pillars' top surface, without negatively affecting cell proliferation. Electrophysiology properties and synapse number of primary neurons are also very well preserved. In perspective, high aspect ratio semiconducting polymer pillars may find interesting applications as soft, photoactive elements for cell activity sensing and modulation. Hybrid interfaces between living cells and nano/microstructured scaffolds have huge application potential in biotechnology, spanning from regenerative medicine and stem cell therapies to localized drug delivery and from biosensing and tissue engineering to neural computing. However, 3D architectures based on semiconducting polymers, endowed with responsivity to visible light, have never been considered. Here, we apply for the first time a push-coating technique to realize high aspect ratio polymeric pillars, based on polythiophene, showing optimal biocompatibility and allowing for the realization of soft, 3D cell cultures of both primary neurons and cell line models. HEK-293 cells cultured on top of polymer pillars display a remarkable change in the cell morphology and a sizable enhancement of the membrane capacitance due to the cell membrane thinning in correspondence to the pillars' top surface, without negatively affecting cell proliferation. Electrophysiology properties and synapse number of primary neurons are also very well preserved. In perspective, high aspect ratio semiconducting polymer pillars may find interesting applications as soft, photoactive elements for cell activity sensing and modulation.

4,4-Difluoro-4-borata-3a-azonia-4a-aza-s-indacene dyes, more commonly known as BODIPY dyes, have been long since recognized for their excellent optical properties such as high absorption coefficients, high fluorescence quantum yields, and remarkable photostability1. Discovered for the first time in 1968 by Treibs and Kreuz2, BODIPY dyes are of wide importance and have a broad use as laser dyes in biological sensing, organic electronic, and other possible applications3. Recently BODIPY molecules dispersed in a polymeric matrix like polystyrene (PS) have been also used to achieve polariton condensation in strongly coupled microcavities4 . Here we present the synthesis, photophysical and gain properties of a series of BODIPY dyes functionalized with lateral substituents to improve their film forming ability and to reduce the effect of PL quenching. This will permit such dyes to be used at high concentration in a strongly coupled microcavity and will allow to reduce the threshold for polariton condensation.

Multilayers of sulphur-based anchoring group linkers and CdSe nanocrystals (NCs) were realized on ITO substrate via layer-by-layer alternation. The materials were investigated by UV-vis and FTIR spectroscopy, photoluminescence and photoconductivity. We found that the change of NCs packing during the multilayers build-up produces a progressive increase of exciton delocalization. In fact during multilayer deposition the NCs first excitonic peak shifts progressively towards longer wavelengths. We found a linear relation between the optical bang gap shift ("?" E_gn) and the inverse of number of CdSe-NCs layers ( n ) for n > 2, in particular the decrease of its value for the infinite multilayer from the one of the solution (2.10 eV) goes from 18 meV for the 1,2-ethylene-bis(dithiocarbamate) (EDTC) linker to 66 meV for sulphide dianions, corresponding to an apparent increase of the exciton radius of 0.20 nm and 0.85nm respectively.

Two branched oligophenylenethynylenes with phenylene or biphenylene moieties as inter-nodal fragments are synthesized by the Sonogashira reaction for optoelectronic applications. The branching of polyphenylenethynylenes influences the electro-optical properties, but cannot be precisely controlled, while its determination is often hardly addressed. The optical investigation, supported by nuclear magnetic resonance (NMR) studies, of oligophenylenethynylenes and the properly synthesized model compounds is performed to get insights on the branching and related effect on the material performance. The proposed branched oligophenylenethynylenes are good ultraviolet emitters in solution, while in solid-state aggregation phenomena strongly affect emission properties. However, the interactions between pi-electrons on phenylene and ethynylene of neighboring molecules in films enhance intermolecular charge transport (hole mobility = 3.2 x 10(-3) cm(2) V(-1)s(-1)) making them optimal candidates as hole transport materials in optoelectronic devices. The insertion of the oligophenylenethynylene film as a hole transporting layer in multilayered solution processes blue, green, and red electroluminescent diodes, enhances OLEDs electro-optical properties.

New acceptor⿿donor⿿acceptor (A-D-A) small molecules consisting of a central thiophene-based donor building block, i.e. 3-dodecyl-thiophene (for NTN) and 3,3⿲⿿-dihexyl-terthiophene (for NT3N), and dinitrophenyl-hydrazone acceptor ends were synthesized. The materials display intense optical absorption spectra with absorption edge down to 1.65 eV. Cyclic voltammetry in solution shows oxidation and reduction processes with HOMO and LUMO energy levels at -5.6 and -3.5 eV. Cyclic voltammetry of NT3N cast films displays an unusual splitting of both oxidation and reduction peaks into two components with the same potential separation (0.45 V). Films of tetrahexyl-sexithiophene, selected as a model compound of NT3N without polar ends, show an analogous albeit much lower (0.13 V) splitting of the first one-electron oxidation process. The co-presence of a crystalline and an amorphous phase in the cast films is believed to be responsible for the splitting, which corresponds to the crystallization energy.

In this work a novel combination of side chain functionalities, alkyl-phosphonate (EP) and alkyl-ammonium bromide (NBr) groups, on a polyfluorene backbone (PF-NBr-EP) was studied as cathode interfacial material (CIM) in polymer-based solar cells. The devices were made with a conventional geometry, with PTB7:PC71 BM as active layer and aluminum as metal electrode. The CIM showed good solubility in ethanol and film forming ability onto the active layer so that its deposition could be finely tuned. The interface engineering imparted by this CIM was assessed and discussed through kelvin probe force microscopy (KPFM), impedance spectroscopy, charge recombination and electron transport characterizations. To discriminate between the interfacial modifications imparted by the interlayer and its solvent, we included in this study a surface ethanol treated device. In the optimized conditions an average power conversion efficiency of 7.24% was obtained, which is about 60% higher when compared to devices made with bare Al and 26% when compared to devices made with a standard calcium/aluminum cathode. Besides performances, some insights about the devices shelf life stability are also presented. A good persistency through aging was found for the cathode interfacial engineering capabilities of PF-NBr-EP.

Push-coating is a green and extremely low-cost process in which only few microliters of conjugated polymer solutions are used to produce thin films using capillary forces. Here, we adapt this fabrication technique to replicate self-assembled nanoporous structures on green and red light-emitting conjugated polymer thin films. These films display ring-like photoluminescence and are successfully integrated into polymer light-emitting devices as emitting layers. At low applied voltages, the green-emitting devices exhibit electroluminescence (EL) from hexagonally arranged nanopixel arrays resulting from a stronger electric field in the thinner areas inside the pores. By gradually increasing the voltage up to 10 V, the emission extends to the areas around the pores. At voltages higher than 10 V, a nonreversible nanopixel to nanoring-like switching of the EL can be observed. After filling the pores with a second blue-emitting conjugated polymer, voltage-dependent reversible color tuning of the EL is achieved in the nanostructured light-emitting bilayers.

Short-channel field-effect transistors (FETs) prepared from semiconducting single-walled carbon nanotube (s-SWNT) dispersions sorted with poly(2,5-dimethylidynenitrilo-3,4-didodecylthienylene) are demonstrated. Electrical analysis of the FETs shows no evidence of metallic tubes out of a total number of 646 SWNTs tested, implying an estimated purity of our semiconducting SWNT solution higher than 99.85%. These findings confirm the effectiveness of the polymer-wrapping technique in selecting semiconducting SWNTs, as well as the potential of sorted nanotubes for the fabrication of short channel FETs comprising from 1 to up to 15 nanotubes without inter-nanotube junctions. Published by AIP Publishing.

4,4-Difluoro-4-borata-3a-azonia-4a-aza-s-indacene dyes, more commonly known as BODIPY dyes, have been long since recognized for their excellent optical properties such as high absorption coefficients, high fluorescence quantum yields, and remarkable photostability1. Discovered for the first time in 1968 by Treibs and Kreuz2, BODIPY dyes are of wide importance and have a broad use as laser dyes in biological sensing, organic electronic, and other possible applications3. Recently BODIPY molecules dispersed in a polymeric matrix like polystyrene (PS) have been also used to achieve polariton condensation in strongly coupled microcavities4 . Here we present the synthesis, photophysical and gain properties of a series of BODIPY dyes functionalized with lateral substituents to improve their film forming ability and to reduce the effect of PL quenching. This will permit such dyes to be used at high concentration in a strongly coupled microcavity and will allow to reduce the threshold for polariton condensation. (1) Wood, T. E.; Thompson, A. Chem. Rev. 2007, 107, 1831-1861. (2) Treibs, A.; Kreuzer, F.-H. Justus Liebigs Ann. Chem. 1968, 718, 208-223. (3) Squeo, B. M.; Gregoriou, V. G.; Avgeropoulos, A.; Baysec, S.; Allard, S.; Scherf, U.; Chochos, C. L. Prog. Polym. Sci. 2017, 71, 26-52. (4) Grant, R. T.; Michetti, P.; Musser, A. J.; Gregoire, P.; Virgili, T.; Vella, E.; Cavazzini, M.; Georgiou, K.; Galeotti, F.; Clark, C.; Clark, J.; Silva, C.; Lidzey, D. G. Adv. Opt. Mater. 2016, 4, 1615-1623.

Colloidal nanoplatelets (NPLs), owing to their efficient and narrow-band luminescence, are considered as promising candidates for solution-processable light-emitting diodes (LEDs) with ultrahigh color purity. To date, however, the record efficiencies of NPL-LEDs are significantly lower than those of more-investigated devices based on spherical nanocrystals. This is particularly true for red-emitting NPL-LEDs, the best-reported external quantum efficiency (EQE) of which is limited to 0.63% (EQE = 5% for green NPL-LEDs). Here, we address this issue by introducing a charge-regulating layer of a polar and polyelectrolytic polymer specifically engineered with complementary trimethylammonium and phosphonate functionalities that provide high solubility in orthogonal polar media with respect to the NPL active layer, compatibility with the metal cathode, and the ability to control electron injection through the formation of a polarized interface under bias. Through this synergic approach, we achieve EQE = 5.73% at 658 nm (color saturation 98%) in completely solution processed LEDs. Remarkably, exposure to air increases the EQE to 8.39%, exceeding the best reports of red NPL-LEDs by over 1 order of magnitude and setting a new global record for quantum-dot LEDs of any color embedding solution-deposited organic interlayers. Considering the emission quantum yield of the NPLs (40 ± 5%), this value corresponds to a near-unity internal quantum efficiency. Notably, our devices show exceptional operational stability for over 5 h of continuous drive in air with no encapsulation, thus confirming the potential of NPLs for efficient, high-stability, saturated LEDs.

Interchain interactions can play a positive role in reaching amplified spontaneous emission in an interesting core-polymer system where the donor (side chains) and the acceptor (core) are chemically linked together. Different degree of interchain interactions modifies the photophysical characteristics of the polymer. By means of transient absorption spectroscopy we show that the stimulated emission from the core decreases passing from solid state to concentrated solution and it is almost absent in the diluted solution. The conformational rearrangements of the core-polymer chain in solution limits the efficiency of the intrachain Förster energy transfer mechanism. The free chain rotations decrease the exciton hopping along the conjugated chains, the ratio between donor and acceptor moieties in the polymer, and change the relative orientation of the transition dipoles of the donor and acceptor causing a strong decrease of energy transfer efficiency and subsequently of the gain.

Polymer wrapped single-walled carbon nanotubes (SWNTs) have been demonstrated to be a very efficient technique to obtain high purity semiconducting SWNT solutions. However, the extraction yield of this technique is low compared to other techniques. Poly-alkyl-thiophenes have been reported to show higher extraction yield compare to polyfluorene derivatives. Here, the affinity for semiconducting SWNTs of two polymers with a backbone containing didodecylthiophene units interspersed with N atoms is reported. It is demonstrated that one of the polymers, namely, poly(2,5-dimethylidynenitrilo-3,4-didodecylthienylene) (PAMDD), has very high semiconducting SWNT extraction yield compared to the poly(3,4-didodecylthienylene)azine (PAZDD). The dissimilar wrapping efficiency of these two polymers for semiconducting SWNTs is attributed to the interplay between the affinity for the nitrogen atoms of the highly polarizable walls of SWNTs and the mechanical flexibility of the polymer backbones. Photoluminescence (PL) measurements demonstrate the presence of metallic tubes and SWNT bundles in the sample selected with PAZDD and higher purity of SWNT-PAMDD samples. The high purity of the semiconducting SWNTs selected by PAMDD is further demonstrated by the high performance of the solution-processed field-effect transistors (FETs) fabricated using a blade coating technique, which exhibit hole mobilities up to 33.3 cm2 V-1 s-1 with on/off ratios of 106.

The ability of a π-stacked polybenzofulvene derivative to self-assemble with emissive dyes in supramolecular organizations that reduce unwanted microaggregation processes is demonstrated by a study of the photophysical properties of its blends with benzothiadiazole and two perylenediimide derivatives. Films displaying efficient emissions with quantum yields of 0.85 in the yellow, 0.54 in the red, and 0.39 in the deep-red regions are obtained thanks to combined homo- and hetero-resonant energy transfer processes from the polymer excimer-like π-stacked chromophores to the emitting dyes.

Interfacial engineering has been recently identified as fundamental strategy for maximizing efficiency and stability of organic electronic devices. To this aim, a new class of water/alcohol soluble materials comprising a ?-conjugated backbone with pendant polar or ionic groups has been recently developed [1]. These polar conjugated polymers have the typical properties of polymeric semiconductors, such as easy processability, chemical tunability, lightness and flexibility, and are suitable for meeting the growing demand for environmentally friendly materials. In fact, the solubility in water and alcohols obtained by the incorporation of polar/ionic side groups can potentially provide increased biocompatibility for sensor applications and more environmentally friendly manufacturing options. Moreover, the possibility for orthogonal solvent processability opens the way to all-solution-processed organic multilayer devices. In this view, we have designed, synthesized and tested a whole series of polar conjugated polymers featuring a fluorene-based backbone with pendant phosphonate and/or amine groups. We present the synthetic strategies we have followed for their synthesis and a few example of their application as charge regulating layer in optoelectronic devices [2].

Two-dimensional (2D) materials have garnered tremendous interest due to their unprecedented physical and chemical properties. Recently, a large family of 2D metal carbides and nitrides (MXenes) have been discovered which exhibits metallic conductivity, hydrophilicity and several other attractive properties. MXenes have already shown a great promise in broad range of applications such as energy conversion and storage, water purification, catalysis, antibacterial agent, transparent conductive electrodes, electromagnetic shielding and others. One way to expand the MXenes applications is to tune their physical, chemical and electrochemical properties by mixing them with polymers to synthesize functional nanocomposites. Therefore, it is necessary to first understand the interaction mechanisms of polymers with 2D MXene layers. Here, we provide a mechanistic insight into interaction of ?-conjugated polymers with titanium carbide, Ti3C2Tx (MXene), using polyfluorene derivatives (PFD) having the same conjugated backbone but different lateral chain from apolar to polar. Three PFD having no polar, with polar nitrogen, and with charged nitrogen functionality were synthesized via the Suzuki polycondensation reaction. Detailed microscopic and spectroscopic results demonstrated that polar polymers with charged nitrogen ends tend to strongly interact with the Ti3C2Tx layers, causing an increase in interlayer spacing and large shifts in spectroscopic peaks. When optimized composites were tested as pseudocapacitive electrodes, improved capacitance values and excellent capacitance retention were observed. Our results provide a valuable insight into exploring new organic materials capable of intercalation between the layers of Ti3C2Tx, and other MXenes for energy storage applications and beyond.

Organic light-emitting diodes (OLEDs) able to directly emit circularly polarized (CP) electroluminescence (CP-OLEDs) are rapidly gaining much interest, due to their possible applications in displays with antiglare filters and 3D displays. Development of more efficient CP-OLEDs can open their use also in point-of-care and personalized diagnostic tools, since CP light alteration can be related to health state of irradiated tissues. In this work it is shown that the performance of chiral europium complex-based CP-OLEDs can be improved both in terms of external quantum efficiency (measured on all the Eu bands) and degree of polarization of emitted photons (as measured by the dissymmetry factor gEL), by proper active layer formulation and through a fine tuning of the architecture of the device. Polarization performances (g(EL) = -1) are obtained about three times higher than for any other CP-OLED reported so far. Moreover, for the first time, it is shown that the position of the recombination zone (RZ) plays a major role on the polarization outcomes. In order to rationalize these results the level of light polarization is related to the position of the RZ allied with the reflection on the cathode through a simple mathematical model. The values predicted by this model are in qualitative agreement with the experimental ones.

Amongst the different optoelectronic applications of conjugated polymers, the development of new active materials for optically pumped organic lasers is still an open question particularly in the blue-near UV spectral range. We investigate the emission properties of poly[(9,9-dioctylfluorene-2,7-dyil)- alt-p-phenylene] (PFP) neat films under nanosecond pump. We demonstrate that thanks to the introduction of a phenylene moiety between two fluorene units it is possible to obtain Amplified Spontaneous Emission (ASE) with a lower threshold and a blue shifted wavelength with respect to poly(9,9-dioctylfluorene) (PFO). We demonstrate efficient ASE with a minimum threshold as low as 23 mu Jcm(-2) and a minimum ASE wavelength of 436 nm. A maximum net optical gain of about 26 cm(-1) is measured at an excitation density of 0.23 mJcm(-2). These results make the PFP a good active material for optically pumped deep blue organic lasers. (C) 2017 Elsevier B.V. All rights reserved.

We report broadband and quasi-omnidirectional antireflective (AR) structures inspired to the nipple arrays of moth eyes. These nanocoatings, based on thin elastomeric films, are prepared by simple self-assembly processing of a co-polymer specifically designed to this purpose, and PDMS replica molding. Typically, their surface is covered by a compact distribution of hemispherical nanodomes of about 250 nm in diameter and about 100 nm in height. When these novel nanostructures are applied on a single glass surface, a maximum of 2% transmission enhancement (equivalent to a 50% reduction of the reflected component) towards wavelengths ranging from visible to near IR region is obtained. A considerable AR power is observed also at a wide range of incident angles ranging from normal to 50 degrees. These properties could be attributed to an optimized graded refractive index profile resulting from the randomly distributed and close-packed nanodomes. Moreover, thanks to their elastomeric nature, these crack-free films can be easily applied on glass, as stickers, and periodically replaced, thus offering the possibility of easy dirt removal from an optical device. KEYWORDS: moth eye, antireflection, nanostructures, breath figures, PDMS, nanofabrication

Two new benzofulvene derivatives bearing a fluorene chromophore in different positions of the phenylindene scaffold were synthesized and induced to polymerize spontaneously. The photophysical investigation evidenced the role of the substitution topology of the monomeric units in the optical properties of the corresponding polymers. In particular, the polymer emission efficiency was found to improve both in solution and in the solid state when the fluorene residue enhances monomer conjugation and rigidity. The ability of this newly synthesized class of polymers to self-organize in supramolecular structures is evidenced through a study on blends with a benzothiadiazole based dye at different concentrations. Aggregation quenching processes of the dye are sharply reduced and complete resonant energy transfer from the polymer to the dye is reached even at 1% dye concentration. The peculiar ability of this new class of pi-stacked polymers to self-assemble in such a supramolecular organization suggests their use as platforms for the design of more complex nanostructured films with enhanced optical and optoelectronic properties.