Optophysical Properties Research Articles

Dinuclear cyclometalated iridium (III) complex containing functionalized triphenylamine core: synthesis, photophysics and application in the single-emissive-layer WOLEDs

To obtain highly efficient white-emitting devices, a novel functionalized dinuclear iridium (III) complex of C8TPA(FIrpic)2 was successfully synthesized and characterized. In this phosphor, FIrpic is a blue-emitting phosphorescent chromophore of iridium(III) bis[(4,6-difluorophenyl)pyridinato-N,C2′] picolate and C8TPA is a blue-emitting fluorescent chromophore of triphenylamine as bridging donor. Its optophysical and electro-phosphorescent properties were primarily investigated. White emission with an increasing current efficiency of 1.31 cd/A at 15.3 mA/cm2 and brightness of 1770 cd/m2 at 656.3 mA/cm2 was obtained in its single-emissive-layer OLEDs with a configuration of ITO/PEDOT:PSS/C8TPA(FIrpic)2 (10 wt %):TCTA/TPBi/LiF/Al. The results indicate that an introduction of triphenylamine group into dinuclear iridium (III) complexes as bridged donor can improve the performance of its iridium (III) complexes-doped OLEDs.

Engineering the Interconnecting Position of Star-Shaped Donor-π-Acceptor Molecules Based on Triazine, Spirofluorene, and Triphenylamine Moieties for Color Tuning from Deep Blue to Green.

Pi-conjugated organic molecules featuring the donor-bridge-acceptor (D-π-A) structure have been widely used in semiconducting materials owing to their rigid structure, good thermal stability, excellent charge transfer, and high emission efficiency. To investigate the effect of the D-π-A molecular structure on the photophysical properties, in this contribution, three star-shaped D-π-A isomers based on the 2,4,6-triphenyl-1,3,5-triazine, spirofluorene, and triphenylamine moieties, that is, p-TFTPA, mp-TFTPA, and m-TFTPA, were synthesized by elaborately engineering the interconnecting position in the building-block units. The optophysical properties of these compounds were systematically explored by experiments and theory calculations. Definitively, changing the interconnecting position in these molecules played a significant role in the degree of π conjugation, which resulted in tunable emission colors from deep blue to green. Moreover, these isomers were employed as emissive dopants in organic light-emitting diodes. The highest external quantum efficiency of 2.3 % and current efficiency of 6.2 cd A(-1) were achieved by using the p-TFTPA based device. This research demonstrates a feasible way to realize blue emitters by engineering D-π-A conjugation.

Creation and characterization of He-related color centers in diamond

Diamond is a promising material for the development of emerging applications in quantum optics, quantum information and quantum sensing. The fabrication and characterization of novel luminescent defects with suitable opto-physical properties is therefore of primary importance for further advances in these research fields.In this work we report on the investigation in the formation of photoluminescent (PL) defects upon MeV He implantation in diamond. Such color centers, previously reported only in electroluminescence and cathodoluminescence regime, exhibited two sharp emission lines at 536.5nm and 560.5nm, without significant phonon sidebands.A strong correlation between the PL intensities of the above-mentioned emission lines and the He implantation fluence was found in the 1015–1017cm−2 fluence range. The PL emission features were not detected in control samples, i.e. samples that were either unirradiated or irradiated with different ion species (H, C). Therefore, the PL features are attributed to optically active defects in the diamond matrix associated with He impurities. The intensity of the 536.5nm and 560.5nm emission lines was investigated as a function of the annealing temperature of the diamond substrate. The emission was observed upon annealing at temperatures higher than 500°C, at the expenses of the concurrently decreasing neutral-vacancy-related GR1 emission intensity. Therefore, our findings indicate that the luminescence originates from the formation of a stable lattice defect. Finally, photoluminescence from He-related defects was observed under different laser excitations wavelengths (i.e. 532nm and 405nm), thus providing promising evidence of a broad spectral range for optical stimulation.

Effects of formamidinium and bromide ion substitution in methylammonium lead triiodide toward high-performance perovskite solar cells

Compositional engineering of organic-inorganic hybrid perovskite has attracted great research interests recently for seeking a better perovskite system to address existed challenges, such as the thermal and moisture instability, anomalous hysteresis, and toxic lead contamination, etc. In this study, we systematically investigated the structural, optophysical, and photovoltaic properties of the compositional MAxFA1−xPb(IyBr1−y)3 perovskite by sequentially introducing FA+ and Br- ions into the parental MAPbI3 to elucidate their respective roles when they were inserted into the perovskite lattice. We unraveled that such dual compositional tuning in perovskite can improve the crystallinity of the resultant film and thus reduce its density of defect states as evidenced by admittance spectroscopy, resulting in a prolonged carrier lifetime over 500ns. As a result, a promising average PCE (PCEAVG) of 17.34% was realized in the optimized MA0.7FA0.3Pb(I0.9Br0.1)3-based PVSC with little hysteresis and stable photocurrent output. More significantly, another compositional MA0.7FA0.3Pb(I0.8Br0.2)3 perovskite with a large bandgap of 1.69eV can yield an impressively high PCEAVG over 15%. To the best of our knowledge, this performance is among the state-of-the-art large bandgap (~1.7eV) PVSCs reported so far, which paves the way for the development of high-performance tandem cells using efficient large bandgap PVSCs as the top subcells. This study not only manifests the pivotal roles of dual compositional tuning in MAxFA1−xPb(IyBr1−y)3 perovskites but also highlights the importance of compositional engineering for developing an even more efficient perovskite.

A Family of Highly Efficient CuI-Based Lighting Phosphors Prepared by a Systematic, Bottom-up Synthetic Approach.

Copper(I) iodide (CuI)-based inorganic-organic hybrid materials in the general chemical formula of CuI(L) are well-known for their structural diversity and strong photoluminescence and are therefore considered promising candidates for a number of optical applications. In this work, we demonstrate a systematic, bottom-up precursor approach to developing a series of CuI(L) network structures built on CuI rhomboid dimers. These compounds combine strong luminescence due to the CuI inorganic modules and significantly enhanced thermal stability as a result of connecting individual building units into robust, extended networks. Examination of their optical properties reveals that these materials not only exhibit exceptionally high photoluminescence performance (with internal quantum yield up to 95%) but also that their emission energy and color are systematically tunable through modification of the organic component. Results from density functional theory calculations provide convincing correlations between these materials' crystal structures and chemical compositions and their optophysical properties. The advantages of cost-effective, solution-processable, easily scalable and fully controllable synthesis as well as high quantum efficiency with improved thermal stability, make this phosphor family a promising candidate for alternative, RE-free phosphors in general lighting and illumination. This solution-based precursor approach creates a new blueprint for the rational design and controlled synthesis of inorganic-organic hybrid materials.

A bisindolylmaleimide-naphthalimide building block for the construction of the energy transfer cassette.

Double build-in chromophores with naphthalimide and bisindolylmaleimide incorporating to one molecule were synthesized efficiently and characterized fully. Its spectral properties were investigated. Effective intramolecular energy transfer together with the strong emission in solution and solid state were discussed in terms of its electronic structures. Optimized structure and frontier molecular orbital were calculated based on D3(mol) platform. Obviously electron delocalization before and after excitation was observed according to the molecular orbital calculation, which corresponds to the mechanism of excitation energy transfer through space occurred in the donor-linker-acceptor molecular system. The opto-physical properties of the dye indicated potential application of electro-optical materials.

Synthesis and optophysical properties of dimeric aza-BODIPY dyes with a push-pull benzodipyrrolidone core.

A series of benzodipyrrolidone-based dimeric aza-BODIPY dyes with a push-pull structure are synthesized. Single crystal X-ray diffraction demonstrates these extended aza-BODIPY dyes are planar. The resulting aza-BODIPY chromophores exhibit intense absorption in the 450-800 nm regions and possess lower-lying LUMO energy levels. Furthermore, the push-pull substituents on aza-BODIPYs core have a positive effect on their optophysical properties.

Comparative study of structural and optical properties of pulsed and RF plasma polymerized aniline films

Abstract Plasma polymerization of aniline is carried out by means of continuous RF and pulsed DC glow discharge plasma in a common reactor at different applied powers. The discharge control variables are optimized for good quality film growth and the role of fragmentation of the molecular structure on the structural, optical, morphological and optophysical properties of the deposited plasma polymerized aniline (PPAni) layers is investigated. Retention of the conjugated structure is found to be prominent at optimum applied power to the plasma in both the continuous RF and pulsed DC polymerization techniques. Improvement in conjugated structure and chain length have been observed in both the continuous RF and pulse DC PPAni thin films with the increase in applied power to the plasma up to a certain limit of applied power when working pressure is fixed at 0.15 mbar. A decrease in optical bandgap with the increase in applied power to the plasma is observed in both the pulsed DC and RF PPAni thin films, but it is more significant in case of RF PPAni films. The plasma polymerized aniline thin films are found to emit photoluminescence due to band to band transition and defects generated in the structure.

Improved photovoltaic performance of two-dimensional low band-gap conjugated polymers with thieno[3,2-b]thiophene and diketopyrrolopyrrole units by altering pendent position of conjugated side chain

Two-dimensional low band-gap copolymers of P1 and P2 with a framework of (2,5-di(thiophen-2-yl)thieno[3,2-b]thiophene)-alt-(2,5-bis(2-ethylhexyl)-3,6-di(thiophen-2-yl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione) (DTTT-alt-DTPP) were synthesized, in which two 2,3-dioctylthiophene-5-yl groups were pended into the 3-positions of two thiophenyl rings close to the thieno[3,2-b]thiophene (TT) unit for P1 and the 3, 6-positions of the TT unit for P2, respectively. The influence of pending positions on optophysical and photovoltaic properties were studied. Similar broad absorption spectra from 350 to 950 nm were observed with a low band-gap of 1.25 eV. However, significantly different photovoltaic properties were obtained in the bulk heterojunction polymer solar cells with a device structure of ITO/PEDOT:PSS/active layer/LiF/Al. The P1-based devices showed a power conversion efficiency (PCE) of 0.79%, but the P2-based devices displayed a notably increasing PCE up to 2.12% under an AM 1.5G irradiation with an intensity of 100 mW cm−2. Our results indicate that altering pendent position of alkyl thiophene is effective way to improve the photovoltaic properties for the two-dimensional copolymers.

σ, m, p-위치로 치환된 Difluoroaniline을 첨가제로 사용한 안의료용 렌즈 고분자의 물리·광학적 특성

σ, m, p-위치로 치환된 Difluoroaniline을 첨가제로 사용한 안의료용 렌즈 고분자의 물리·광학적 특성

Novel iridium complexes containing alkylfluorene functionalized picolinic acid ancillary ligand: Synthesis, optophysics and electroluminescence properties

Two novel green-emitting cyclometalated iridium complexes of (Buppy)2Ir(Tfl-pic) and (Buppy)2Ir(Brfl-pic) were synthesized and characterized, in which Buppy is 2-(4-tert-butylphenyl)pyridine, Tfl-pic is 6-(6′-(9″-octyl-2″,7″-bi(9,9-dioctylfluoren-2-yl)fluoren-9″-yl)hexyloxy) picolinic acid and Brfl is 6-(6′-(2″,7″-di-bromo-9″-octylfluoren-9″-yl)hexyloxy) picolinic acid. Their thermal property, dispersibility and optophysical properties were investigated. Both iridium complexes present intense UV absorption bands and photoluminescence performance in CH2Cl2. Single-emissive-layer polymer light-emitting devices using (Buppy)2Ir(Tfl-pic) and (Buppy)2Ir(Brfl-pic) as a single dopant and a blend of poly(vinylcarbazole) and 2-(4-biphenyl)-5-(4-tert-butyl-phenyl)-1,3,4-oxadiazole as the host matrix were fabricated. The (Buppy)2Ir(Tfl-pic)-doped devices exhibited a maximum current efficiency of 2.44 cd A−1. As expected, the phase separation and concentration quenching of these iridium complexes in the devices are efficiently suppressed due to appending bulky fluorene derivatives on the picolinic acid unit by a non-conjugated connection.

Novel cyclometalated platinum (II) complex containing carrier-transporting groups: Synthesis, luminescence and application in single dopant white PLEDs

Abstract In order to investigate the influence of carrier-transporting groups on the luminescent properties, especially on excimer/aggregation emission, and to obtain single emissive dopants used in white polymer light-emitting diodes with a single emissive-layer structure, two novel platinum complexes derived from a platinum(II) (2-(4′,6′-difluorophenyl)pyridinato-N,C2′)(picolinate) unit containing carrier-transporting groups were synthesized and characterized, where a triphenylamino or an oxadiazole-triphenylamino functionalized unit was pending into the picolinate by non-conjugated linkage, respectively. Their optophysical, electrochemical and electroluminescent properties were investigated. Compared to their parent platinum complex, both functionalized platinum complexes exhibited a significantly red-shifted photoluminescent profile in neat film and higher photoluminescent quantum efficiency in dichloromethane at room temperature. Furthermore, the platinum complex with oxadiazole-triphenylamino ambipolar transporting group exhibited better photoluminescent properties and offered potential application as a single dopant in a single emissive-layer-based white polymer light-emitting diode. More stable white light emissions were observed in this platinum complex-doped devices at dopant concentrations of 4–8 wt%. The maximum luminous efficiency of 1.01 cd A−1 and the maximum brightness of 2177 cd m−2 were obtained in the polyfluorene-hosted devices.

Glass–film-combination: Opto-physical properties and energy saving potential of a novel greenhouse glazing system

A combination of anti-reflection coated glass and ethylene tetrafluoroethylene film is introduced as a novel glazing system for greenhouses and similar buildings. It combines the advantages of the individual materials (durability/low weight; favourable condensation behaviour/self-cleaning) and of single and double layer systems (light transmission/insulation). By inflating/deflating the glass–film interspace, the additional insulation can be switched on and off. Since no standard method for this purpose is available, a hot box-system was developed to measure heat transfer coefficients (U-values) of different models of the glass–film-combination (GFC) and other commonly used greenhouse glazing materials at different surface inclinations; with or without condensation. Surface inclination did not greatly influence heat transfer. Condensation increased the U-values more pronounced for single layer-systems than for the GFC. Influences of wind velocity on heat transfer decreased with the degree of insulation. Overall, when mounted with adhesive tape, the energy efficiency of the GFC was 38% higher compared to customary float glass. The energy saving potential of plastic profile mounted GFC versions was 50% and 64% for the double and triple layer system (ETFE-film on both sides of the glass pane), respectively. PAR transmission of the GFC was similar to single pane float glass, its UV transmittance markedly higher.

Highly Dichroic Metallomesogen of Dinuclear Platinum Complex: Synthesis and Liquid Crystal and Photophysical Properties

A novel dinuclear platinum complex of (biC12ppy-fl)Pt2C12DBM)2 with liquid crystal luminescent property has been prepared, as well as its liquid crystal, optophysical properties and hole mobility have been studied, where biC12ppy-fl is 6,6′-[4,4′-(9,9-didodecyl-9H-fluorene-2,7-diyl)bis(1,4-phenylene)]bis[3-(dodecyloxymethyl)pyridine] and C12DBM is 1,3-bis[4-(dodecyloxy)phenyl]propane-1,3-dione. This dinuclear platinum complex displayed a smectic mesophase and excellent opto-physical properties. Compared to the reported mononuclear platinum complex of (CnROppy)Pt(acac) (R = H, F), this dinuclear platinum complex exhibited higher emission quantum yield and higher stability, as well as higher hole mobility of 8.4 × 10–4 cm2/(V s). Moreover, a highly polarized ratio of 10.3 was obtained for the aligned film of (biC12ppy-fl)Pt2(C12DBM)2 on the aligned polyimide at room temperature.

Harmonizing Triplet Level and Ambipolar Characteristics of Wide-Gap Phosphine Oxide Hosts toward Highly Efficient and Low Driving Voltage Blue and Green PHOLEDs: An Effective Strategy Based on Spiro-Systems

A series of phosphine oxide (PO) hosts based on diphenylphosphine oxide and spiro[fluorene-9,9′-xanthene] (SFX) moieties, SFX2PO, SFX27PO, SFX2′PO, and SFX2′7′PO, were designed and synthesized. On the basis of the different electrical properties of xanthene and fluorene in SFX, the influence of substitution position on the chemical and optophysical properties of the ambipolar-core based systems were investigated in detail. The effective strategy of introducing electron-withdrawing PO moieties in electron-deficient moieties in the molecules accompanied with suitable linkages insulating the electron-rich and -deficient moieties was convincingly demonstrated, which can endow the hosts with much better carrier injecting and transporting ability and high enough T1 for blue and green phosphors. As the results, the operating voltages of the devices based on SFX2PO and SFX27PO were much lower than those of the devices based on SFX2′PO and SFX2′7′PO. Simultaneously, the efficiencies of the SFX2PO based devices wer...

Gold nanoparticles in the clinical laboratory: principles of preparation and applications

In order to meet the challenges of effective healthcare, the clinical laboratory is constantly striving to improve testing sensitivity while reducing the required time and cost. Gold nanoparticles (AuNPs) are proposed as one of the most promising tools to meet such goals. They have unique optophysical properties which enable sensitive detection of biomarkers, and are easily amenable to modification for use in different assay formats including immunoassays and molecular assays. Additionally, their preparation is relatively simple and their detection methods are quite versatile. AuNPs are showing substantial promise for effective practical applications and commercial utilization is already underway. This article covers the principles of preparation of AuNPs and their use for development of different diagnostic platforms.

Synthesis and Opto‐electronic Properties of a Red‐Emitting Heteroleptic Platinum Complex Using Pyrazol‐based Diketone Derivative as Ancillary Ligand

AbstractA red‐emitting heteroleptic cyclometalated platinum(II) complex containing an ancillary ligand of pyrazol‐based diketone derivative was synthesized. Its optophysical and electroluminescent properties were studied. Compared to the reported (piq)Pt(acac) complex, this platinum(II) complex exhibited a blue‐shifted UV absorption band at 300–450 nm, a low LUMO energy level and improved electroluminescent property. Using this platinum(II) complex as a single doping emitter and a blend of ploy(9,9‐dioctylfluorene) and 2‐tert‐butylphenyl‐5‐phenyl‐1,3,4‐oxadiazole as a host matrix, the fabricated polymer light‐emitting devices displayed saturated red emission with a peak at 648 nm and a shoulder at 601 nm. Furthermore, the emission quenching of the platinum(II) complex was significantly suppressed in these devices at high current density due to an introduction of the non‐planar pyrazol group into the ancillary ligand.

Significantly improved photovoltaic performances of the dithiophene‐benzothiadiazole‐alt‐fluorene copolymers by incorporating carbazole units in fluorene moiety

AbstractTo exploit an effective way to improve polymeric photovoltaic performance, a series of dithiophene‐benzothiadiazole‐alt‐fluorene copolymers containing carbazole groups at C‐9 positions of the alternating fluorene units (PFO‐FCz‐DBT) were synthesized and characterized. The effect of the carbazole groups on the optophysical, electrochemical, and photovoltaic properties of these copolymers was investigated. By comparison, this type of copolymers with carbazole units exhibited significantly improved photovoltaic properties than poly(2,7‐(9,9‐dioctyl‐fluorene)‐alt‐5,5‐(4′,7′‐di‐2‐thienyl‐2′,1′,3′‐benzothiadiazole) (PFO‐DBT) in the bulk heterojunction solar cells. A maximum power‐conversion efficiency (PCE) of 2.41% and a highest short‐circuit current density (Jsc) of 9.68 mA cm−2 were obtained for the PFO‐FCz‐DBT30, which are about two times higher than the corresponding levels for the PFO‐DBT30. This work demonstrated that introducing a hole‐transporting carbazole unit into copolymer is a simple and effective method to improve the Jsc and PCE. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

Synthesis and photophysical properties of three (multi)branched planar molecules

Three thiophenevinyl substituted one-, two-, and three-branched truxene π-conjugated compounds TS1, TS2 and TS3 have been prepared using a Heck reaction. Their linear absorption, single- and two-photon excited fluorescence were examined. The three analogues emit blue fluorescence at 420 nm. The number of branches has no influence on the position of the absorption maxima of the charge transfer band and fluorescence emitting maxima. However, the molar extinction coefficients of charge transfer band increase almost linearly with the number of branches. The two-photon absorption cross-section of the octupolar three-branched compound TS3 is several times that of the two-branched compound TS2 and one-branched compound TS1.

Metallomesogens based on platinum(ii) complexes: synthesis, luminescence and polarized emission

Two series of heteroleptic cyclometalated platinum(II) complexes [(C(n)Oppy)Pt(acac) and (C(n)OFppy)Pt(acac)] have been prepared. Their liquid-crystal and optophysical properties were studied, in which C(n)Oppy is 2-(4-alkoxyphenyl)-5-(alkoxymethyl)pyridine and C(n)OFppy is 2-(3-fluoro-4-alkoxyphenyl)-5-(alkoxymethyl)pyridine. Only the heteroleptic cyclometalated platinum(II) complexes (n = 12 and 16) exhibited enantiotropic mesophase transitions with smectic (S(m)) structure. Intense polarized luminescence with a maximum peak at 532 nm and a polarization ratio as high as 10.5 were obtained in an aligned polyimide film under opto-excitation at room temperature. This research work provides a simple approach to realize high-efficiency polarized emission by heteroleptic cyclometalated platinum(II) complexes.