P-dimethyl Aminostyryl Research Articles

Simultaneous enhancement of photocurrent and open circuit voltage in ternary organic solar cells by red fluorescent material as third component materials

Ternary organic solar cells (OSCs) were constructed using D18-Cl:Y6 as the host photoactive layer and the red fluorescent material [4-(dicyano-methylene)-2-methyl-6-(p-dimethyl aminostyryl)-4H-pyran] (DCM) as the third component material. The optimized ternary OSCs (optimized weight ratio of D18-Cl:Y6:DCM is 1:1.4:0.1) showed a power conversion efficiency (PCE) of 17.36 %, a short-circuit current density (JSC) of 26.79 mA cm−2, an open-circuit voltage (VOC) of 0.89 V, and a fill factor (FF) of 72.8 %. Since the absorption peak of DCM is located in the red light region and the photoluminescence peak of DCM is covered by the absorption peak of D18-Cl, DCM significantly improves the short-wavelength light absorption of the optimized ternary photoactive layer and facilitates the energy transfer from DCM to D18-Cl. While increasing the DCM content, the LUMO level of the blend acceptor is shifted upwards, which favors the VOC value. However, excessive amount of DCM would damage the phase separation, bulk and surface morphology of the ternary film. The results showed that the red fluorescent material DCM has great potential as a third component material for realizing highly efficient ternary OSCs.

White organic light-emitting devices with tunable color emission fabricated utilizing exciplex formation at heterointerfaces including m-MDATA

The electrical and the optical properties of organic light-emitting devices (OLEDs) fabricated utilizing a 4,4′,4″-tris(2-methylphenyl-phenylamino)triphenylamine (m-MTDATA) were investigated to clarify the effect of exciplex on their color stabilization and color purity. The electrons combined with the holes at heterointerfaces between the m-MTDATA layer and the 9,10-di(2-naphthyl)anthracene (MADN) and the 4-(dicyanomethylene)-2-methyl-6-(p-dimethyl aminostyryl)-4H-pyran (DCM1) emitting layer (EML) resulted in the formation of the exciplex. The emission peak of the electroluminescence spectra for the OLEDs fabricated utilizing the m-MTDATA layer shifted to a lower energy side in comparison with that of the EML. This was due to the interaction of the holes in the m-MTDATA layer and the electrons in the MADN EML. Carriers in white OLEDs (WOLEDs) with exciplex emissions existed at the heterointerfaces between the m-MTDATA and the EML because the DCM1 EML was too thin to affect the EL peak related to the m-MTDATA layer. The Commission Internationale de l'Eclairage coordinates of WOLEDs at 9.5 V were (0.33, 0.36), and their maximum current efficiency at 46 mA/cm 2 was 2.03 cd/A.

Undoped White Organic Light-Emitting Diodes Utilizing Two Sources of Excitons

We report two undoped white organic light-emitting diodes with the structures of ITO/m-MTDATA/Alq3/NPB/BCP/Alq3/Mg:Ag (device A), and ITO/NPB/DCM/NPB/Alq3/NPB/BCP/Alq3/Mg:Ag (device B), where ITO is indium tin oxide, m-MTDATA is 4,4',4''-tris{N,(3-methylphenyl)-N-phenylamino}-triphenylamine, Alq3 is tris(8-hydroxyquinoline) aluminum, NPB is N,N'-di(naphth-2-yl)-N,N'-diphenyl-benzidine, BCP is 2,9-dimethyl-4,7-diphenylphenanthroline, and DCM is 4-(dicyanomethylene)-2-methyl-6-(p-dimethyl aminostyryl)-4H-pyran. Red emission was harvested from the exciplex at the m-MTDATA/Alq3 interface and DCM (0.5 nm) for devices A and B, respectively, while green and blue emissions were from Alq3 and NPB respectively, for both devices. A maximum brightness of 1100 and 4500 cd/m2 was achieved at a current density of 270 mA/cm2 (12 V) for devices A and B, respectively. Device B showed a maximum external quantum efficiency of 0.89% photon/electron (2 cd/A), which is about four times of that of device A.

Efficient electrofluorescent organic light-emitting diodes by sequential doping

The authors reported a highly efficient electrofluorescent organic light-emitting diode fabricated by sequential doping. An archetypal device utilizing 4-(dicyanomethylene)-2-methyl-6-(p-dimethyl aminostyryl)-4H-pyran as dopant in a matrix of tris-(8-hydroxyquinoline) aluminum was investigated. The emission layer consists of a few repeating cells, similar to a multiple quantum well structure, which are made of sequentially evaporated host and dopant. An external quantum efficiency as high as 3.38% photons/electron was obtained. By avoiding coevaporation, sequential doping should render better control on device performance and day-to-day repeatability.

Wavelength dependence of irreversible photobleaching of dye-doped polymer waveguide materials

We report the irreversible bleaching characteristics of 4-(dicyanomethylene)-2-methyl-6-(p-dimethyl aminostyryl)-4H-pyran (DCM) doped into perfluorocyclobutene (PFCB) and a new material known as DH-6 doped into amorphous polycarbonate (APC) by a monochromatic bleaching source. The wavelength dependent rate constants for the irreversible bleaching process are found, and the experimental bleaching characteristics are compared to the theoretical bleaching characteristics determined from a kinetic model of the bleaching process.

Investigation of dye-doped red emitting organic electroluminescent devices with metal-mirror microcavity structure

Organic electroluminescent (EL) devices with planar microcavity structure, indium-tin-oxide/Ag∕N,N′-diphenyl-N , N ′-bis(3-methylphenyl)-1,1′-biphenyl-4 , 4′-diamine/tris(8-hydroxyquinoline)-aluminum (AlQ):4-(dicyanomethylene)-2-methyl-6-(p-dimethyl aminostyryl)-4H-pyran/AlQ∕LiF∕Al, were fabricated. The Ag and Al layers acted as not only hole-injection layer and cathode, respectively, but reflective mirrors, resulting in strong microcavity effects, such as spectral narrowing and directional emission. The effects of device parameters on the EL performance were studied in detail and were discussed in terms of conventional microcavity theory. On-axis light magnification with a coefficient (EL enhancement ratio between cavity and noncavity devices) of ∼5 was observed, which was consistent with the theoretical calculation. At the same time, optimized microcavity device with bright pure red emission showed maximum luminance of 5140cd∕m2, peak at 624nm, Commission International de I’Eclairage coordinates of x=0.663 and y=0.336, and high EL efficiency of 1.71cd∕A were obtained.

Kinetic model of irreversible photobleaching of dye-doped polymer waveguide materials

We consider the irreversible photobleaching of guest–host polymer combinations, those of benzocyclobutene and perfluorocyclobutene doped with 4-(dicyanomethylene)-2-methyl-6-(p-dimethyl aminostyryl)-4H-pyran. The time evolution of the absorption spectrum bleached by the 514-nm line of an Ar+-ion laser can be described by a change in amplitudes of the observed Gaussian-shaped absorption features as a function of the applied photobleaching dose. A phenomenological model that describes this time evolution compares favorably with the experimental data. A discussion of the reasons that so simple a model may be applicable to polymer systems doped with stilbenelike dyes is made.

A nondoped-type small molecule white organic light-emitting device

We fabricated a small molecule nondoped white organic light-emitting device whose structure included indium tin oxide glass substrate/50 nm N, N′-bis-(1-naphthyl)-N, N′-diphenyl-1,1′-biphenyl-4,4′-diamine hole transporting layer/0.05 nm 4-(dicyano-methylene)-2-methyl-6-(p-dimethyl aminostyryl)-4H-pyran/25 nm 4,4′-bis(2,2′ diphenyl vinyl)-1,1′-biphenyl/15 nm tris(8-hydroxyquinoline) aluminium electron transporting layer/0.5 nm lithium fluoride/aluminium. It showed a maximum power efficiency of 1.74 lm W−1 at 6 V (the brightness is 125 cd m−2 and the CIE 1931 chromaticity coordinates are (0.34, 0.36)). Its brightness reaches 3750 cd m−2 at 15 V. And the chromaticity coordinates, varying from (0.36, 0.38) to (0.30, 0.32) with increasing forward bias from 4 to 15 V, are well within the white region.

Design and development of organic light emitting diodes

A highly luminescent thiophene based conjugated polymer, i.e., poly[2-(3-thienyl) ethanol butoxy carbonyl–methyl urethane] (PURET) has been used for fabricating polymeric light emitting diodes in the present investigations. PURET has been doped with varying amount of (4-dicyano methylene-2 methyl-6-(p-dimethyl amino styryl)-4H-pyran) dye. Enhanced electroluminescence (EL) and quantum efficiency has been observed by incorporating small amount of dye. An attempt has been made to understand the mechanism of charge transport, which helped in the understanding of the possible reasons for enhancement of EL emission as a function of dye concentration and allowed for further optimization of device performance. Based on capacitance–voltage (C–V) analysis it is proposed that the devices in the present investigations, may be modeled as a resistance and capacitor in parallel for the frequency range of 20 Hz–1 MHz. The enhancement in EL intensity and external quantum efficiency of PURET has been observed in addition of small amount of dye which is attributed to the trapping of excitons and enhanced probability electron–hole recombination in EL layer. In addition, voltage tunable color emission has also been observed. This is attributed to the charge transport among the various layers depending upon the applied voltage.

Nondoped-type white organic electroluminescent devices utilizing complementary color and exciton diffusion

We fabricated nondoped white organic electroluminescent devices using vacuum-deposited thin films of blue-emitting 4,4′-bis[N-1-napthyl-N-phenyl-amino]biphenyl (α-NPD) and orange-emitting 4-(dicyanomethylene)-2-metyl-6-(p-dimethyl aminostyryl)-4H-pyran (DCM), a hole-blocking layer of 2-(4-biphenyl)-5-(p-tert-butylphenyl)-1,3,4-oxadiazole (tBu-PBD) and electron-transporting tris(8-quinolinolato) aluminum (III). Excitons formed at the α-NPD/tBu-PBD interface sequentially transfer their energy to α-NPD via the Förster mechanism. The exciton is captured by an ultrathin DCM layer located within the pure α-NPD layer. The position of the DCM determines the device spectrum, and enables a white emission to be achieved. The spectrum is not sensitive to the voltage applied, and the devices show maximum luminance of about 1000 cd/m2.

Bright small molecular white organic light-emitting devices with two emission zones

Bright multilayer organic light-emitting devices (OLEDs) containing both perylene-doped [4,4′-bis(9-carbazolyl) biphenyl (CBP)] and [4-(dicyano-methylene)-2-methyl-6-(p-dimethyl aminostyryl)-4H-pyran (DCM1)-doped tris-(8-hydroxy quinoline) Al (Alq3)] are described. The electroluminescence spectra consist of blue and green bands at 453, 487, and 524 nm due to perylene and a red band at 600 nm due to DCM1, although these two emitting layers are separated by a layer of [2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (Bu-PBD)]. As the thickness of the hole-injecting [N,N′-diphenyl-N,N′-bis(1-naphthyl-phenyl)-1, 1′-biphenyl-4,4′-diamine (NPB)] and perylene:CBP layers increases and that of the DCM1:Alq3 layer decreases the perylene emission intensifies strongly relative to the DCM1 emission. For 350 Å thick NPB, 350 Å thick perylene:CBP, 100 Å Bu-PBD, and 150 Å DCM1:Alq3, the brightness reaches 3750 Cd/m2 at 20 V, the efficiency is 2.4 Cd/A at 19 V, and the (x,y) CIE coordinates are well within the white region. However, as the bias is increased the intensity of the perylene emission increases relative to the DCM1 emission. Both the layer thickness and bias dependence are believed to result from changes in the recombination zone and in the field- and cathode-mirror-induced quenching of DCM1 singlet excitons.

Fluorescence and EPR studies on the collapse of poly( N-isopropyl acrylamide)- g-poly(ethylene oxide) in water

Studies on the thermal behaviour of copolymers, poly( N-isopropyl acrylamide), PNIPA, grafted with different amounts of poly(ethylene oxide), PEO, were conducted in aqueous solutions by fluorescence and EPR spectroscopies. The grafting reaction had been conducted under various reaction conditions and the number of PEO grafts per a PNIPA chain varied from 6 to 10. A fluorescence probe, 4-(dicyano methylene)-2-methyl-6-( p-dimethyl amino styryl)-4H-pyran (4HP) was observed to localise in the hydrophobic parts of the polymers. The changes in the polarity and microviscosity in the surroundings of 4HP upon the collapse of PNIPA depended in general on the amount of PEO in the polymer, polymer concentration, and sample-heating rate. However, fluorescence data revealed differences between the polymers, owing to the varying distribution of the PEO grafts along the PNIPA main chain. The polymer grafted in water at an elevated temperature ( T∼LCST) differed clearly from the others, those synthesised either in cold water or in an organic solvent. This particular polymer formed dense local hydrophobic domains inside the collapsed globule. Two ways of preparing the samples for EPR measurements resulted in a different localisation of a spin probe 5-doxyl stearic acid in the polymers. The probe resided either in the outer PEO shell close to the aqueous phase or in a less polar phase close to the PNIPA core of the polymer. The rate of the rotational diffusion of the radical increased discontinuously during the polymer collapse in the former case but in the latter, a typical linear activation of the thermal motion was observed. The results strongly suggest that the distribution of the PEO grafts along the PNIPA chains depends on the conformation of the functionalised PNIPA during the grafting, and this affects the behaviour of the graft copolymers.

４‐ジシアノメチレン‐２‐メチル‐６‐（ｐ‐ジメチルアミノスチリル）‐４Ｈ‐ピランとポリ（Ｎ‐ビニルピロリドン）との相互作用

We succeeded to solubilizing 4-dicyanomethylene-2-methyl-6-(p-dimeth ylaminostyryl)-4 Hpyran (DCM) in poly(N-vinylpyrrolidone) (PVP) aqueous solution, but its fluoresent intensity one hundredth decreased.From the equi librium constant between DCM and PVP, it was assumed that the interaction between DCM and PVP is due to the hydrogen bond between NH, group of DCM and C=0 group of PVP.The mechanica l properties and fluorescent wavelength of the film which was casted from the system of DCM-PVP aqueous solution differed from the film which was casted from the system of DCM-PVP DMSO solution.

Organic photoconductors: Dark and photoconduction studies in two p-dimethylamino styryl dyes derived from pyridine-2 and pyridine-4

Results of our experiments on the dark and photoconduction studies in two p-dimethylamino styryl dyes derived from pyridine-2 (PDMS-P2) and pyridine-4 (PDMS-P4) in their pure form without any dopant or additive are reported. Measurements on surface-type (raster pattern) cells show that the dark and photocurrents are dependent on the applied potential, temperature, and the photocurrent on the intensity of the incident radiation and the wavelength. Action spectra of the samples could not be recorded as the intensity of the monochromatic radiation from the monochromator reaching the sample was too low to induce any noticeable photocurrent. The compounds show a low dark conductivity. The dark and photocurrents show a perfect ohmic behaviour in the temperature range studied (288–328 K). Since photoconduction could only be observed in a vacuum, this clearly indicates that the compounds are n-type semiconductors. The observed rise and decay kinetics of the photocurrents indicate the presence of traps in the forbidden zone. The dyes show an enhanced photoconduction on illumination with visible radiation only. The marked open circuit voltage and the short-circuit current observed in these compounds indicate a possible application in solar photovoltaics.

Structural dependence on the photovoltaic and the photoconduction behaviour of some P-dimethylamino styryl dyes derived from different heterocyclic nuclei

The results on the structural dependence of the photovoltaic and the photoconduction behaviour of seven P-dimethylamino styryl dyes derived from different heterocyclic nuclei is reported. It has been confirmed that the plane-to-plane stacking of the molecules in the solid state enhances the π-electron overlap and hence to the higher photovoltaic and the photoconduction behaviour observed in these compounds.

The antiseptic and trypanocidal action of certain styryl and anil quinoline carboxylamides.*

In the case of quaternary compounds of the styryl quinoline series and of the analogous benzthiazole derivatives a powerful trypanocidal effect in vivo has been shown to depend on the presence in the substance of a free basic group in one of the nuclei, and anacylamino (especially acetyl) or urethane group in the other, and also on the styryl linkage—each playing a definite part in contributing to the action (Browning, Cohen, Ellingworth and Gulbransen, 1929, 1931). This is exemplified by 2( p -aminostyryl)-6 acetylamino quinoline methochloride (No. 8), 2( p -dimethylamino styryl)-6 acetylamino quinoline methochloride (No. 25), 2( p -acetylamino)-6 dimethylamino quinoline methochloride (No. 90) and 2( p -dimethylamino styryl) quinolyl (6) urethane (Me) methochloride (No. 125). The effect of acetylation of the amino group parallels that dis­covered by Ehrlich and his co-workers in the case of p -amino phenyl arsinic acid. Gough and King (1930) have recently made the important observation that in the latter series the introduction of an amide group converts the therapeutically inactive carboxylic and sulphonic acids into active compounds. Accordingly, the effect of substituting a carboxylamide group for the acylamino in compounds of the type of No. 25 and its anil analogue (No. 62) has been investigated. In addition, the position of the carboxylamide group has been varied. These substances were further examined for antiseptic action, the results being shown in the table. Trypanocidal properties have been tested on T. brucei infections in mice as in previous work. The striking observation has been made that only those compounds with the carboxylamide group in the 6 position are therapeutically active, the anils being only slightly less effective than the styryl analogues ( cf . Nos. 410, 409 and 385, 403). This contrasts with what is found in the acetylamino derivatives, since the styryl compounds of the latter are highly active as compared with the corresponding anils. The carboxy-ethylamides (420, 419) are more toxic and less trypanocidal than the corresponding amides and methylamides.