摘要:

Dried oriented Purple-Membrane (PM)-films were fabricated by electrosedimentation of aqueous PM-suspensions on ITO-covered slides. The photoelectric signals of illuminated films were used to switch twisted-nematic (TN)- and ferroelectric (FE) liquid-crystal (LC) cells. Due to the quasi differential behaviour of the photocurrent with respect to illumination intensity, a PM/TN system represents an inherent novelty filter. The use of FE-LC cells for permanent data display is demonstrated and a prototype of a pixelated BR-LC-OASLM is presented.

ISSN:1058-725X    

DOI:10.1080/10587259808044323

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

We synthesized some aromatic ester oligomers consisting of repeating units of oxy-1,4-phenylenecarbonyl group (ArESn, n=2∼4) as novel nonlinear optical (NLO) active chromophores and their methacrylate derivatives (ArESn-MA, n=2∼3). Some second-order NLO properties for poled polymer films of poly(methyl methacrylate) doped with 10 or 5wt%ArESn(ArESn/PMMA) andArESn-MAhomopolymers(poly(ArESn-MA))as well as copolymers with MMA(poly(ArESn-MA-co-MMA))were estimated by the second harmonic generation (SHG) measurement using Nd-YAG laser as light source. Comparison of thed33value at the chromophore molar concentration (d33(M)) forArESn/PMMAfilms indicated that thed33(M) value ofArESnincreases with increase in n andArESnwith n more than 3 reveal higherd33(M) value than that ofpNA, in addition, everyArESnhas cutoff wavelength (λco) of about 300nm, which is much snorter than the case ofpNA (λco=ca. 450nm). Moreover,poly(ArESn-MA)films exhibited much largerd33values than those ofArESn/PMMAfilms since the formers contain the chromophores in high concentration, however, when the comparison is made by using thed33(M) value the values become less than 1/2 of those in the cases ofArESn/PMMAfilms. This might be caused by a strong interaction acting among the chromophore side chains. Copolymerization ofArESn-MAwith MMA which is capable of relieving the interaction improved the chromophore orientation considerably.

ISSN:1058-725X    

DOI:10.1080/10587259808044324

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Emissive behaviors from the systems with the sizes of the order of visible wavelength are described. Control of electrically-pumped emission from thin-film electroluminescent devices by use of one-dimensional planer cavities is demonstrated. Photoluminescence behaviors from organic dielectric stacks with buried emissive centers prepared by vacuum-vapor deposition were examined. Photoluminescence from self-organized three-dimensional ordered arrays of polystyrene small particles with luminescent dyes is also studied. In both systems, inhibition of spontaneous emission due to photonic gaps were observed.

ISSN:1058-725X    

DOI:10.1080/10587259808044325

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Photoactiveorganicthin films are attracting rapidly growing attention. Model investigations are aiming at establishing a new era of electronics, based on molecular materials – with the potential of miniaturization down to the molecular level (“molecular electronics”). As a fundamental difficulty, however, electric, photoelectric and optoelectronic properties of organic thin film samples are often found to vary considerably with the preparation parameters. – Using vapor-deposited 3,4,9,10-perylene-tetracaboxylic- dianhydride (PTCDA) thin films and measuring the electron time-of-flignt mobility we prove that, what appears as poor reproducibility, largely is a consequence of a wide scatter of structural parameters, such as the degree of cystallinity and orientational order. We find that the electron mobility – over orders of magnitude – is (anti-)correlated with the width of the X-ray rocking curve of the respective sample, reaching 3×10-2cm2/Vs for our presently best one.

ISSN:1058-725X    

DOI:10.1080/10587259808044326

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Results are presented of a study on luminescence quenching, by an applied electric field, of x-form metal-free phthalocyanine and type II chlorogallium phthalocyanine, both of which are highly efficient photocarrier generating material. Experimental results, especially the time dependence, indicate that the quenching of the fluorescence seems to be the effect of photogenerated charges, rather than induced by an electric field. An irreversible decrease of the fluorescence intensity occurs under prolonged illumination with electric field applied.

ISSN:1058-725X    

DOI:10.1080/10587259808044327

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Intense white photoluminescence from C60composite films observed under green laser irradiation is found to be closely connected with local defective structures incidentally formed during the film fabrication process. On the basis of the finding, we succeeded in introducing such emissive structures by intentional mechanical scratching. White electroluminescence was also observed at such modified structures. A possible mechanism of such unusual light emission is discussed.

ISSN:1058-725X    

DOI:10.1080/10587259808044328

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Photoinduced inter- and intramolecular electron transfer reactions of methylene-linked (n) carbazole and terephthalic acid methyl ester (abbreviated as D-(n)-A, n=4 and 12) have been examined by using external electro-modulated fluorescence spectroscopy and photocurrent measurement, which allow one to obtain information about the Stark shift and the efficiency of fluorescence quenching as well as photocarrier generation induced by an electric field. The action spectra of the photocurrent could be successfully measured at various concentrations in the absorption region of carbazole (240–365 nm). The obtained action spectra agree well with the simultaneously measured fluorescence excitation spectra, indicating that photocarrier generation occurs following the relaxations including internal conversion to S1and excitation energy migration among carbazole chromophores. Furthermore, the efficiency of photocarrier generation of D-(12)-A is higher than that of D-(4)-A, indicating that an intramolecular recombination process plays an important role in charge recombination of a photogenerated ion-pair state.

ISSN:1058-725X    

DOI:10.1080/10587259808044329

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Exciplex formation at the organic solid-state interface in an organic electroluminescent device has been studied. A new multilayer device consisting of the electron-transport layer of 1,3,5-tris(4-tert−butylphenyl-1,3,4-oxiadiazolyl)benzene (TPOB) and double hole-transport layers of 4,4′,4′-tris(3-methylphenylphenylamino)triphenylamine (m−MTDATA) andN,N′−bis-(3-methylphenyl)-N,N′−diphenyl-[1,l′-biphenyl]-4,4′-diamine (TPD) sandwiched between the electrodes of an alloy of magnesium and silver and indium tin oxide (ITO) emitted bright bluish-green light resulting from the exciplex formed at the interface between TPOB and TPD. The exciplex formation is evidenced by the measurement of the photoluminescence spectra of spin-coated films of TPOB, TPD, and a mixture of TPOB and TPD and their photoluminescence lifetimes.

ISSN:1058-725X    

DOI:10.1080/10587259808044330

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Dynamics of formation and deactivation processes was discussed for extremely long-lived (>8h) charge-separated states following photo-induced electron transfer in carbazolyl vinyl polymers, poly(N-vinylcarbazole), poly(7-vinylbenzo[c]carbazole, and poly(5-vinylbenzo[b]carbazole), coadsorbed with 1,2,4,5-tetracyanobenzene as an electron acceptor on a macroreticular resin, Amberlite XAD-8, at room temperature.

ISSN:1058-725X    

DOI:10.1080/10587259808044331

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The electron injection process was investigated for poly(methylphenylsilane) (PMPS) in two-layer light-emitting diodes (TL-LEDs) composed of a PMPS film and a vacuum-deposited film of oxadiazole molecules (OXDs). The latter acts as an electron injection layer. The basic characteristics of the TL-LEDs were markedly better than those of single-layer LEDs. The magnitude of the accompanying red-shift in the EL spectrum coincides with the energy difference between the conduction band and/or the one-dimensional exciton level of PMPS, and the conduction band of an OXD layer. This study has revealed that electron injection in PMPS is an energy selective process occurring via surface defect levels which exist below the conduction band of the OXD layer in terms of energy, and that the electron-hole recombination takes place in the PMPS layer near the interface with the OXD layer.

ISSN:1058-725X    

DOI:10.1080/10587259808044332

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor