Thermal and optical properties of red luminescent glass forming symmetric and non symmetric styryl-4H-pyran-4-ylidene fragment containing derivatives

Abstract Dyes with amorphous structure deposited from organic solvents and having good fluorescence properties show potential for photonic device applications. Organic glass-forming symmetric and non symmetric styryl- derivatives of 2(2,6-substituted-4H-pyran-4-ylidene)-malononitrile (it has backbone of known laser dye 4-(dicyanomethylene)-2-methyl-6-[p-(dimethylamino)styryl]-4H-pyran), 2(2,6-substituted-4H-pyran-4-ylidene)-1H-indene-1,3(2H)-dione and 2(2,6-substituted-4H-pyran-4-ylidene)-pyrimidine-2,4,6(1H,3H,5H)-trione were synthesized and investigated. Glass transition temperatures higher than 110 °C were achieved. The absorption bands in dichloromethane solution cover the spectral regi…

Photoinduced phenomena in corona poled polar organic films.

Abstract Organic materials have received considerable attention because of their large dipole moments and optical nonlinearities. The optically induced switching of material properties is important for studying the optoelectronic effects including second harmonic generation. Organic materials for photonic applications contain chromophore dipole which consist of acceptor and donor groups bridged by a delocalized π-electron system. Both theoretical and experimental data show a reversible highly dipolar photoinduced intra molecular charge transfer in betaine type molecules accompanied by change of the sign and the value of the dipole moment. The arrangement of polar molecules in films is studi…

<title>Optically induced switching of dicyclohexylamino substituted azobenzene derivatives in thin ordered films</title>

During the last years, there has been an increasing interest in the photoinduced switching effects. Among the objects of concern azobenzene derivatives, isomerizing under UV and visible light, occupy a prominent position. To understand the photoresponse of these materials in the condensed phase, their spectroscopic and electrical properties are studied. It is shown that the photoresponse depends on the orientation of the molecules and their packing. A number of novel azobenzene derivatives containing a N,N-dicyclohexyl sulfonamide moiety is synthesized. The derivatives differ in the length of alkyl chains between the azobenzene moiety and SH or COOH groups. The morphology and the photoinduc…

Pyranylidene indene-1,3-dione derivatives as an amorphous red electroluminescence material

The organic light-emitting diode (OLED) has promising applications in flat-panel displays and novel light sources. Thus far, OLED structures have mostly been made by thermal evaporation in vacuum. An alternative approach is to use small molecules that form amorphous (glassy) structures from solutions. Such compounds can be used in ink-jet printing technologies and result in reduced OLED prices. We present an original red fluorescent organic compo- und 2-(2-(4-(bis(2-(trityloxy)ethyl)amino)styryl)-6-methyl-4H-pyran-4-ylidene)-1H-indene-1, 3(2H)-dione (ZWK1), and its derivative 2-(2,6-bis(4-(bis(2-(trityloxy)ethyl) amino)styryl)-4H- pyran-4-ylidene)-1H-indene-1,3(2H)-dione (ZWK2), where the m…

Bi-Layer GaOHPc:PCBM/P3HT:PCBM Organic Solar Cell

International Conference on Functional Materials and Nanotechnologies (FM&NT2012)

The International Conference Functional Materials and Nanotechnologies (FMN ferroics; multiscale and multiphenomenal material modeling and simulation 2. Nanotechnologies including progressive methods, technologies and design for investigation of nanoparticles, nanostructures, nanocomposites, thin films and coatings; 3. Energy including perspective materials and technologies for renewable and hydrogen energy, fuel cells, photovoltaics and developing diverse energy systems. A special section devoted to Organic Materials was organized to commemorate a long-time organizer of the FM&NT conference series, Dr. habil. phys, academician Inta Muzikante who passed away on 15 February 2012. The number …

Photoelectrical Properties and Energetical Structure of Thin Films of Indandione Derivatives

A sandwich type structure of two dimetilaminobenziliden-1,3-indandione (DMABI) derivatives placed between metal electrodes was made to investigate the photoelectrical properties of these derivatives. DMABI is an organic isolator with a wide energy gap and high quantum efficiency of the photogeneration, DMABI derivatives have received also considerable attention because of its large dipole moment and optical nonlinearities. Besides, since it is a photosensitive material, its use in solar systems is very promising. The energy gap of each material and combined system was observed from the spectral dependence of the quantum efficiency of the photoconductivity and results are compared with resul…

Electrodes for GaOHPc:PCBM/P3HT:PCBM bulk heterojunction solar cell

Abstract The bulk heterojunction approach appears to be one of the most promising concepts of creating efficient, low cost and easily producible organic solar cells. For this purpose one of the best materials was regioregular poly-3-hexylthiophene (P3HT), which is widely used as a donor molecule and a hole transporter, with soluble fullerene derivative (PCBM) as an acceptor and electron transporter. The main drawback of this highly efficient blend is its limited spectral range, covering only a 350–650 nm spectral interval. So the main aim of the present work was to extend the spectral range of the cell up to 850 nm by adding a second bulk heterojunction layer of complementary absorption spe…

Light-emitting thin films of glassy forming organic compounds containing 2-tert-butyl-6-methyl-4H-pyran-4-ylidene

Low molecular mass organic compounds which make thin films from volatile organic solutions would be great benefit in future organic light emitting systems. Two most important advantages could be mentioned. First - the repetition of synthesis of small molecules is better than for polymers. Second - wet casting methods could be used. In this work we are presenting optical, electroluminescence and amplified spontaneous emission properties of four original glassy forming compounds containing 2-tert-butyl-6-methyl-4H-pyran-4-ylidene fragment as backbone of the molecule. They has the same N,N-dialkylamino electron donating group with incorporated bulky trityloxy ethyl groups. The difference of th…

Energy structure and electro-optical properties of organic layers with carbazole derivative

Abstract Phosphorescent organic light emitting diodes are perspective in lighting technologies due to high efficient electroluminescence. Not only phosphorescent dyes but also host materials are important aspect to be considered in the devices where they are a problem for blue light emitting phosphorescent molecules. Carbazole derivative 3,6-di(9-carbazolyl)-9-(2-ethylhexyl)carbazole (TCz1) is a good candidate and has shown excellent results in thermally evaporated films. This paper presents the studies of electrical properties and energy structure in thin films of spin-coated TCz1 and thermally evaporated tris[2-(2,4-difluorophenyl)pyridine]iridium(III) (Ir(Fppy)3). The 0.46 eV difference …

<title>All-optical poling of DMABI molecules in a polymer matrix</title>

Many organic compounds in solid state have nonlinear optical properties due to the orientation of the molecules in a polymer matrix. In this work, all-optical poling and second harmonic generation in a composition consisting of 1 mass% of N,N-dimethylaminobenzylidene 1,3-indandione (DMABI) compound in poly(methyl methacrylate) (PMMA) matrix were studied. Thin films were prepared by solvent casting. The 1.064-μm fundamental and 532-nm second harmonic wavelengths of a Nd:YAG laser were used. It is shown that DMABI molecules can be oriented by the method of all- optical poling, and that the process is related to the photoinduced switching between two equally stable states of the molecule.

Energy structure of thin films of carbazole derivatives with metal electrodes

Study of charge carrier transport in organic electroluminescent devices, organic photovoltaic devices, and organic field-effect transistors is one of the most important points. In order to realize comparable electron and hole transport in thin organic films with electrodes the energy structure of such devices are of great importance. In this work, we have studied electrical properties and energy structure of two carbazole derivatives. The threshold energy of photoconductivity quantum efficiency is 2.90 eV and optical energy gap is 3.3 eV in thin films is obtained. The values of work function of ITO, Au, Cu and Pd electrodes are energetically close to conductivity level of holes and holes in…

A noncentrosymmetric crystal structure of a zwitterionic compound, pyridinium 5,7-dihydro-5,7-dioxo-6H-cyclopenta[b]pyridin-6-ylide, realized by weak hydrogen bonds

Abstract Crystal structures of pyridinium 1,3-dihydro-1,3-dioxo-2 H -inden-2-ylide (PI) of a zwitterionic molecule and its nitrogen substituted compounds, 4N-PI and 5N-PI, were solved with X-ray diffraction analyses. Whereas PI and 5N-PI showed centrosymmetric crystal structures, 4N-PI demonstrated a noncentrosymmetric crystal structure where all the molecules orient to almost the same direction. To elucidate the stability of such a polarized structure, we examined interatomic close contacts among the nearest neighbor molecules in the crystals and calculated intermolecular interaction energies with relation to those contacts. As a result, the noncentrosymmetric crystal structure of 4N-PI tu…

Studies of host-guest thin films of corona-poled betaine-type polar molecules by kelvin probe technique and atomic force microscopy

In this work betaine-type molecules were investigated. As a result of the asymmetry of charge distribution, molecules possess in the ground state a considerable permanent dipole moment. The decay of surface potential of poled polymer films is dependent at least on two relaxation processes. The influence of glass transition of PMMA on thermal dependence of the surface potential is shown. The transition temperature, where no changes of the surface potential appeared, is related to glass transition temperature of the host-guest system. The topography of the film surface was obtained by AFM.

Nanocomposites for Novel Sensing Systems

The work performed under the National Research Program of Latvia and presented here is about advanced, chemical stimuli responsive materials. Sensor materials are produced on the basis of metallophthalocyanines or zirconia nanocrystals with the purpose of detecting small size molecular compounds like NH3, O2 and O3. Polymer/nanostructured carbon composite is produced to detect large size molecular compounds like organic vapour. Basic gaseous compound sensing principles are discussed within this paper.

Synthesis, optical, and thermal properties of glassy trityl group containing luminescent derivatives of 2-tert-butyl-6-methyl-4H-pyran-4-one

In this work we present simple preparation of original trityl group containing glassy luminescent 6-styryl substituted derivatives of 2-(2-tert-butyl-4H-pyran-4-ylidene)malononitrile (DWK-1TB), 2-(2-tert-butyl-4H-pyran-4-ylidene)-2- ethyl-2-cyanoacetate (KWK-1TB), 2-(2-tert-butyl-4H-pyran-4-ylidene)-1H-indene-1,3(2H)-dione (ZWK-1TB) and 5-(2-tert-butyl-4H-pyran-4-ylidene)pyrimidine-2,4,6(1H,3H,5H)-trione (JWK-1TB). Their optical properties have been investigated. The absorption maxima of synthesized glasses is in region from 425 nm to 515 nm and emission maxima is from 470 nm to 625 nm in solution of dichloromethane. But absorption maxima of their solid films is from 425 nm to 500 nm and em…

Light induced processes in thin films of indandione type organic molecules

The optically induced switching of material properties is important for investigations of opto-electronic effects and optomechanical properties. Investigated organic materials contain chromophore dipole consisting of acceptor and donor groups bridged by a delocalized p-electron system. Both calculations and experimental data show a reversible highly dipolar photoinduced intra molecular charge transfer in indandione type molecules (DMABI) accompanied by change of the sign and the value of the dipole moment. Investigations of optical properties of thin host-guest polymer films show that the photoinduced process of DMABI is related to the photoinduced switching between two equally stable state…

PV effect of fullerene/poly(3-hexylthiophene) blend sensitized by phthalocyanine having infrared absorption CT band

An attempt was made to extend the photosensitivity spectral range of fullerene/poly(3-hexylthiophene) blend to NIR region by adding extra electron donor — hydroxygallium phthalocyanine (GaOHPc) with a strong and wide intermolecular charge transfer (CT) band around 830 nm. Multilayer cells of ITO/PEDOT: PSS/6 GaOHPc/P3HT: C61(CO2Et)2 have been prepared by spin coating with vacuum evaporated Al or In top electrodes. Significant photosensitivity of the cells was in 370–900 nm spectral range. However charge carrier photogeneration efficiency was 3 times higher for illumination in P3HT absorption band as compared with the GaOHPc CT band at 830 nm. But when GaOHPc was mixed in the blend forming P…

Fluorescence and amplified spontaneous emission of glass forming compounds containing styryl-4H-pyran-4-ylidene fragment

Potential of glassy films of newly synthesised low molecular weight organic molecules for light amplification and lasing applications has been investigated by analysing fluorescence, transient differential absorption and amplified spontaneous emission properties. These non-symmetric and symmetric molecules contain styryl-4H-pyran-4-ylidene fragment with three different electron acceptor groups: dicyanomethylene, barbituric acid, indene-1,3-dione. Fluorescence quantum yields of the investigated compounds in solutions are between 0.32 and 0.54, while they drop down by an order of magnitude in thin solid films. Incorporation of bulky side groups reduced excitonic interactions enabling manifest…

Fluorescence quenching by trapped charge carriers in N,N-dimethylaminobenzylidene 1,3-indandione films

Effects caused by the applied voltage on the steady state and time-resolved fluorescence of vacuum evaporated N,N-dimethylaminobenzylidene 1,3-indandione films sandwiched between gold and aluminium electrodes were investigated and discussed. Fluorescence enhancement and quenching as well as the fluorescence band narrowing depending on the applied voltage have been observed. Fluorescence decay and recovery take place on a time scale of tens of seconds after voltage is switched on and off. Similar fluorescence decay also takes place after switching on the excitation light. These fluorescence changes are attributed to the exciton quenching by trapped charge carriers.

Photoinduced switching of electrical properties in thin films of polar indandione type organic molecules

The optically induced switching of organic materials with large dipole moments consisting of acceptor and donor groups bridged by a delocalized π-electron system is important for investigations of optoelectronic effects. To the contrary of azobenzene molecule, photoinduced change of dipole moment of indandione molecule does not need free volume in thin films. To modify the dipole moment and also to optimise properties of film formation, a number of novel indandione derivatives is investigated. Reversible switching of the surface potential of polymer films with incorporated or chemically attached indandione molecules is observed at irradiation in photoinduced intramolecular electron transfer…

A Novel Gas Sensor Transducer Based on Phthalocyanine Heterojunction Devices

Abstract: Experimental data concerning the changes in the current-voltage (I-V) perfor-mances of a molecular material-based heterojunction consisting of hexadecafluorinated nickel phthalocyanine (Ni(F 16 Pc)) and nickel phthalocyanine (NiPc), (Au|Ni(F 16 Pc)|NiPc|Al) are introduced as an unprecedented principle of transduction for gas sensing performances. The respective n - and p -type doped-insulator behaviors of the respective materials are supported, owing to the observed changes in surface potential (using the Kelvin probe method) after submission to electron donor (ammonia) and electron acceptor gases (ozone). On the other hand, the bilayer device exhibits strong variations in the bui…

Optical and electrical properties of oriented thin films of oligomer containing betaine-type moiety in side chain

Non-linear optical and electrical properties of polymer films obtained by dipole orientation of active units are reported. Novel polar oligomer with N-(indan-1,3-dion-2-yl)pyridinium betaine (IPB) as a side group is studied. Orientation of polar groups in oligomer thin films causes an increase of the photo-induced change of surface potential on irradiation in the region of photo-induced electron transfer (PIET) where the IPB group exhibits a reversible change of the value and sign of the dipole moment. At longer wavelengths, the value of the surface potential of the oligomer may be determined by transport of photogenerated charge carriers.

NLO Polymers Containing as Active Chromophore in Dandionylpyridinium, Betaine Units: Synthesis, Modeling and Characterization

In present article we report about synthesis, quantum chemical model calculations, non-linear optical characterization and dependencies of the surface potential changes on irradiation with light of novel polyurethane based polymers, namely a bipolar organic compound N-(indan-1,3-dion-2-y1)-4-N’,N’dialkylaminopyridinium betaine (IPB) containing charged electron donor and electron acceptor groups covalently bonded to polyurethane polymer backbone. These newly synthesized IPB containing polymers could be regarded as a promising thermally stable organic non-linear optical materials with long time performance for photonic applications.

Impact of aggregates on excitation dynamics in transparent polymer films doped by dipolar molecules

Abstract Optical properties of transparent polymer films of polymethylmethacrylate doped (up to 25 wt.%) by dipolar N , N -dimethylaminobenzylidene 1,3-indandione (DMABI) molecules were studied. Formation of DMABI nanocrystallites, increasing in their density and size with dopant concentration, was revealed by optical microscopy. Transformation of the fluorescence spectrum from the molecular-like emission (for the low dopant concentration below 1 wt.%) to highly red-shifted fluorescence corresponding to self-trapped excitons in the crystallites was observed. It was shown, that due to the resonant energy transfer in the blend, the DMABI nanocrystals can serve as efficient fluorescence marker…

PV and magnetic field effects in poly(3-hexylthiophene)-fullerene cells doped with phthalocyanine soluble derivative

An attempt was made to widen the photosensitivity spectral range of poly(3-hexylthiophene)-fullerene blend by adding an extra electron donor — a newly synthesized soluble phthalocyanine derivative (SnClPc) having the electron absorption band at 708 nm. As the electron acceptor, home-synthesised di(ethoxycarbonyl) methano-fullerene carboxylate (C 61 (CO 2 Et) 2 ) was used, and as the hole transporter — the regioregular poly 3-hexylthiophene (P3HT). The sandwich-type samples were prepared on an ITO glass substrate by coating it with a 30–50 nm thick PEDOT:PSS layer followed by a ~100 nm thick P3HT:C 61 (CO 2 Et) 2 :SnClPc blend. For the top electrodes In or Au were used. Spectral dependences …

Photoelectrical properties of thin films of DMABI derivatives

Organic thin films with semiconducting properties have been intensively studied in nowadays due to very promising applications in organic electronics, for example, organic photovoltaic. Among organic semiconductors, group of indandiones with their photoelectrical properties, thermal and chemical stability are good candidates for use in design of novel molecular electronic devices. We have investigated photoconductivity quantum efficiency and its spectral dependence of two dimetilaminobenzylidene-1,3-indandione derivatives. Values of the photoconductivity threshold energy and optical energy gap are obtained. These results are compared with calculated transfer energy gap estimated according t…

Polymers films with indandione derivatives as alternatives to azobenzene polymers for optical patterning

Surface relief gratings (SRGs) on organic thin films are studied extensively for both scientific interest and in relevance to the applications. Among the chromophores being used the azobenzenes showed the best performance, but the use of alternative photo-sensitive groups provides better general understanding of the phenomena. A thermodynamic theory and molecular dynamics simulations of photoinduced effects are discussed. In this study we use indandione derivatives, known as promising materials for photonics applications, as an alternative to the azobenzenes. We consider their photoreactions when incorporated into a polymer film. One of interesting features is the spectral dependence of the…