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We report the effect of a poly[(9,9-bis(3′-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctyl fluorene)] (PFN) interlayer on the performance of PTB7:PC71BM-based organic thin-film solar cells (OTFSCs) prepared using the spray-coating method. The active layer shows a broad absorption, but the effective contact area in the bulk hetrojunction (BHJ) is small because of the formation of aggregates on the surface. The surface aggregates dissolved by the addition of 1,8-diiodooctane (DIO) to the PTB7:PC71BM matrix, which results in an increase in the contact area between the donor and acceptor in the active layer and, thereby , an improvement in the device performance. The PFN interlayer enhances the charge-transport properties and suppresses exciton-recombination processes. This results in increases in the short-circuit current density (Jsc = 13.87 mA/cm2), open-circuit voltage (Voc = 0.747 V), and fill factor (FF = 57.97%), as a result of a high power conversion efficiency (PCE, η = 6.01%) compared ...

The PTB7 : PC71BM polymer based solar cells have been successfully fabricated by spin and spray coating technique using chlorine-free solvent (xylene), which are desirable to reduce environmental issues. The surface morphology of fabricated film characterized by AFM reveals that the surface morphology of the film is uniform and smooth when xylene is used as compared with chlorobenzene. The highest power conversion efficiency (PCE) (5.07 ± 0.6) was achieved using spray-coating technique than that of spin coating technique (PCE of 4.47 ± 0.6). The enhancement in the performance of the polymer solar cell could be attributed to the improved charge carrier transportation due to additive. The combination of chlorine-free solvent and spray-coating method minimize the waste material and reduce the environmental problem in large-area production of organic solar cells (OSCs).

Organic single crystal of benzyl carbamate was grown by transparent vertical Bridgman technique. The grown crystal was subjected to single-crystal XRD, optical transmittance analysis, second harmonic generation analysis, laser damage threshold and photoconductivity analysis. The grown crystal cell parameters were confirmed by single-crystal X-ray diffraction analysis. From the UV–Vis–NIR transmittance spectrum analysis the cut off wavelength was found to be 275 nm. The second harmonic generation property of the powdered benzyl carbamate was confirmed by the emission of green light. The powder density value of benzyl carbamate crystal was found to be 0.955 GW/cm2. Benzyl carbamate showed positive photoconductivity nature and the calculated photosensitivity value was 2.84.

Fluorine doped ZnO nanopowders were synthesized from starting solutions having different doping levels of F (0, 5, … , 20 at.%) using a simple soft chemical route and the effects of the doping level on the structural, optical, surface morphological and antibacterial properties were investigated. The XRD studies reveal that all the products have preferential orientation along the (1 0 1) plane. The PL studies show that all the samples exhibit strong visible emission with a peak at 425 nm. The enhancement in the visible emission indicates an increasing number of surface defects caused by the doping of F. The obtained FTIR spectra confirm the incorporation of F into ZnO lattice. From the SEM studies, it is observed that the ZnO nanowires formed at 10 at.% of F doping level exhibit excellent antibacterial activities. Antibacterial activity of F doped ZnO nanopowders against Staphylococcus aureus was found to be significantly higher than that against the Escherichia coli and Pseudomonas aeruginosa micro-organisms. All the physical properties were corroborated well with the findings related to antibacterial activity. Finally, we conclude that, the analysis of all the results shows that F doping level of 10 at.% is optimal in all respects and is suitable for antibacterial applications.

Organic thin film solar cells (OTFSCs) were fabricated with blended active layers of poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl]] (PTB7)/[6,6]-phenyl-C71-butyric (PC71BM). The performances of active layers are prepared in chlorobenzene (CB) with different additives of 1-chloronaphthalene (CN) and 1,8-Diiodooctane (DIO) by a wet process with spin coating technique. The effects of different solvent additives on photovoltaic parameters such as fill factor, short circuit current density, and power conversion efficiency of active layers are reported. The absorption and surface morphology of the active layers are investigated using UV-visible spectroscopy and atomic force microscopy, respectively. The results indicate that structural and morphological changes were induced by the additives with solvent. The current density-voltage (J-V) characteristics of photovoltaic cells were measured under the illumination of simulated solar light with 100 mW/cm2(AM 1.5 G) by an Oriel 1000 W solar simulator. The OTFSCs of PTB7/PC71BM prepared with organic solvent additives of DIO+CN show more improved PCE of 4.96% by spin coating method.

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), a conducting polymer, has been receiving a great deal of attention for next generation optoelectronic organic devices. In this report, we discuss the effect of additives along with the thickness of PEDOT:PSS layers on the power conversion efficiency of organic solar cell devices. PEDOT:PSS films treated with high boiling point solvents of dimethyl sulfoxide (DMSO) and ethylene glycol (EG) show a significant enhancement in electrical conductivity without compromising flexibility or optical transparency. The conductivity increased from 0.5 to 517 and 724 S/cm after once and thrice treatment with 4 vol. % EG, respectively. The as-prepared and additives-treated PEDOT:PSS films deposited on glass substrates have been investigated by optical spectroscopy, micro-Raman spectroscopy and atomic force microscopy (AFM). The results indicate that structural and morphological changes were induced by the additive processes. By using DMSO and EG treated PEDOT:PSS as a hole transport layer, organic solar cells with a Poly[[9-(1-octylnonyl)-9H-carbazole-2,7-diyl]-2,5-thiophenediyl-2,1,3-benzothiadiazole-4,7-diyl-2,5-thiophenediyl]:[6,6]-phenyl-C71-butyric acid methyl esters (PCDTBT:PC71BM) bulk heterojunction have been fabricated on indium-tin-oxide (ITO) coated glass substrates. The high power conversion efficiency (PCE) of 5.17%, and 5.69%, were observed for PEDOT:PSS hole transport layers treated with DMSO and EG respectively, even though the devices were prepared in air atmosphere.

In the present work, we have demonstrated high-performance organic solar cells with spray coated active layers. The influence of the nanomorphology on the power conversion efficiency of poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl] [3-fluoro-2-[(2-ethylhexyl)carbonyl] thieno[3,4-b]thiophenediyl]] (PTB7):[6,6]-phenyl-C71-butyric acid (PC71BM) methyl ester bulk heterojunction solar cells is presented. Active layers were prepared using a chlorobenzene solvent containing a small volume of 1,8-diiodooctane as an additive by spray coating with conventional handheld airbrushes. The surface morphology of the active layers deposited for various spray-coating times was examined using atomic force microscopy. The resulting devices were measured under AM 1.5G (100 mW/cm2) conditions in an ambient atmosphere. The optimized spray-coated PTB7:PC71BM film showed a high solar cell performance with a short-circuit current density of 14.20 ± 0.41 mA/cm2, a fill factor of 56.00 ± 0.02% and a power conversion efficiency of 5.96 ± 0.15%.

Organic solar cells have been significantly attracted due to the need to develop an inexpensive clean and sustainable renewable energy source. We report on the fabrication of poly [N-9″-hepta-decanyl-2,7-carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)]/[6, 6]-phenyl-C71-butyric acid methyl ester blend active layer using airbrush spray-coating method in mixed solvents. Optical absorption of the active layers was analyzed using UV–visible spectral studies in the wavelength range from 300 to 800 nm. The surface morphology of the active layers deposited with different parameters (spraying time and substrate-nozzle distance) was examined using atomic force microscopy. The current density–voltage (J–V) characteristics of photovoltaic cells were measured under the illumination of simulated solar light with 100 mW cm−2 (AM 1.5G) by an Oriel 1000 W solar simulator. The power conversion efficiency of the solar cell is more than 5 %.

We investigated the effect of additives on the morphology of a poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b′]dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)] (PCPDTBT):(6,6)-phenyl C71-butyric acid methyl ester (PC71BM) blended onto a surface of poly (3, 4-ethylendioxythiophene): poly(styrensulfonate)(PEDOT:PSS) to form photoactive films. Films of PCPDTBT: PC71-BM bulk heterojunctions were prepared by spin-coating from a solution in chlorobenzene (CB) and were processed with and without the addition of 2%, 4%, and 6 vol% 1-chloro naphthalene (CN) or 1, 8-octanedithiol (ODT) as additives. For all samples, the PCPDTBT:PC71BM molar ratio was 1:2 (wt%), and the additives in 1 ml were prepared with a concentration of 30 mg of PCPDTBT:PC71BM. Optical absorption spectroscopy measurements of the films indicated shifts in the absorption peaks in the range from 500–800 nm which was attributed to PCPDTBT. XRay diffraction (XRD) was used to investigate the nature of the molecular stacking in the polymer thin films. Topographic images which were obtained by using an atomic force microscope, of the PCPDTBT:PC71BM layers with 2 vol% ODT additive, were found to have the highest surface roughness. The best performing device shows a power conversion efficiency of 2.15% for a 2-vol% ODT additive.

Fluorinated copper-phthalocyanine (F16CuPc) thin films were prepared by using a vacuum evaporation technique and were applied to n-type organic field-effect transistors (OFETs) as active channel layers combined with a spin-coated polycarbonate thin-film gate insulator. The output characteristics of the resulting n-type OFET devices with bottom-gate/bottom-contact structures were investigated to evaluate the performances such as the field effect mobility (µFE), the on/off current ratio (Ion/off), and the threshold voltage (Vth). A relatively high field effect mobility of 6.0 × 10−3 cm2/Vs was obtained for the n-type semiconductor under atmospheric conditions with an on/off current ratio of 1 × 104 and a threshold voltage of 5 V. The electron mobility of the n-type semiconductor was found to depend strongly on the growth temperature of the F16CuPc thin films. X-ray diffraction profiles showed that the crystallinity and the orientation of the F16CuPc on a polycarbonate thin film were enhanced with increasing growth temperature. Atomic force microscopy studies revealed various surface morphologies of the active layer. The field effect mobility of the F16CuPc-OFET was closely related to the crystallinity and the orientation of the F16CuPc thin film.

Organic solar cell devices were fabricated using poly[9-(1-octylnonyl)-9H-carbazole-2.7-diyl]-2.5-thiophenediyl-2.1.3-benzothiadiazole-4.7-diyl-2.5-thiophenediyl] PCDTBT/ [6,6]-phenyl butyric acid methyl ester (PC71BM) active layer deposited by spin coating. Moreover, the relationship between solar cell performance and buffer layer thickness was investigated by spin coating speed and AFM imaging of the buffer layer surface. The performance of the organic solar cell with spin-coated active layer was then evaluated, and the power conversion efficiency of the solar cell was determined to be > 5%.

Bulk heterojunction organic solar cell devices were fabricated using the spray deposited poly [N-9″-hepta-decanyl-2,7-carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)]/[6,6]-phenyl-C61-butyric acid methyl ester blend active layer. The spray coating parameters such as spraying time, substrate-nozzle distance for the deposition of active layers were analyzed. Optical absorption of the active layers was analyzed using UV–visible spectral studies in the wavelength range from 300 to 800 nm. The surface morphology of the active layers deposited with different parameters was examined using atomic force microscopy. Surface morphology of the active layers deposited with the substrate-nozzle distance of 20 cm and for 20 s shows smooth morphology with peak-valley value of 4 nm. The devices fabricated using the selected active layer show overall power conversion efficiency of 1.08%.

Vanadyl phthalocyanine (VOPc) thin films are fabricated using molecular beam epitaxy (MBE) technique on KBr (001) substrate preheated at different temperatures under vacuum. VOPc thin films on the KBr substrate cleaved in air and then preheated in vacuum are investigated using scanning electron microscopy (SEM) images and UV-vis absorption spectra. VOPc thin films depend upon preheating temperature of KBr substrate. Large VOPc grains appear in the background of small crystals on the substrate preheated at low temperatures, while more small grains appear on the substrate preheated at higher temperatures and the film is smoothly and epitaxially grown. The preheating at high temperatures removes adsorbed gasses from the substrate. The effecs of preheating indicate that gas molecules adsorbed on the KBr substrate strongly affect the morphology of the VOPc thin film. The third-order nonlinear optical susceptibilities χ(3) (-3ω; ω, ω, ω) of the epitaxial and pseudomorphic VOPc films were determined using the Maker fringe technique.

Poly(3-octylthiophene)/polymethylmethacrylate (P3OT/PMMA) composite thin films were prepared by spin coating as composing a prism-coupling waveguide. The optical absorption property of the composite thin film was evaluated using UV-visible spectra in the range 300-900 nm. The optical bistable characteristics of the prism-coupling waveguide composed of P3OT/PMMA composite film was measured for different input laser power intensities using optical bistable measuring equipment. The optical bistability of the waveguide was measured using a Nd:YAG laser with a wavelength of 1,064 nm, pulse width of 5 ns and a repetition frequency of 10 Hz. The optical bistable characteristics of P3OT/PMMA composite waveguides for different input power intensities shows good stability and hysteresis characteristics. However, in terms of the input laser power dependence of optical bistability, the switching on-off position shifts with the increase in input power intensity. In addition, the effect of organic gas treatment and PMMA molecular weight on the optical bistable characteristics of P3OT/PMMA composite waveguides was investigated.

Regioregular poly(3-hexylthiophene) [RR-P3HT] thin films were prepared on fused quartz glasses by spin-coating and drop-casting from the chloroform solutions. Film structures and morphologies were characterized by UV-visible absorption spectra, out-of-plane X-ray diffraction (XRD) and atomic force microscopy (AFM). Drop-cast films showed increased χ(3) of about three times higher than that of the spin-coated ones when the film thicknesses were both around 140 nm, and the magnitude of the increase was different for different thickness. The magnitudes of χ(3) for drop-cast RR-P3HT films were calculated in the range of 10-11 esu, and the phases of χ(3) lay in the range from 230 to 300° which were consistent with the contributions from two-photon absorptions (TPA). Hexamethyldisilazane (HMDS) treatment of the glass substrates could increase the χ(3) of drop-cast films further from about ten percent to several times higher. This also depended on the film thickness. These results revealed the deposition method and surface modification effects on the self-assembled RR-P3HT film structures, and the importance of higher-ordering and increased crystallinity for the enhancement of the χ(3) of the polymeric films for their applications in NLO devices.

Organic field-effect transistors (OFETs) were fabricated with a high-dielectric-constant and high-permittivity titanium dioxide (TiO2) as a gate insulator and regioregular poly(3-hexylthiophene-2,5-diyl) (RR-P3HT) as the electronically active semiconductor. Positive OFET characteristics were obtained with a low threshold voltage (+3 V) and high field-effect mobility (3.73 ×10-3 cm2 V-1 s-1). The dielectric material (TiO2) was prepared by the sol–gel technique and the gate insulator layer was fabricated by spin coating. The RR-P3HT thin films were fabricated by drop casting with different solution concentrations. The thickness of the thin films was measured using the surface profile measuring system. The fabricated thin film structure was analyzed by atomic force microscopy (AFM), X-ray diffraction (XRD), and UV–visible absorption spectra. The X-ray result shows that the drop-cast RR-P3HT thin film has a high crystallinity on the TiO2 surface, which leads to the high field-effect mobility of the OFET. The results show that the OFET performances are not only dependent on the orientation and crystallinity of the polymer semiconductor, but that also the gate dielectric properties, surface roughness, and interface properties between the gate and semiconductor layers are very important for the efficient performance of the OFET.

Owing to advancing large-scale optical communications technology, all-optical devices have attracted attention in high-speed data communication systems. We measured the characteristics of the optical bistability of elements fabricated using a terthiophene/poly(methyl methacrylate) (PMMA) composite film and a prism, and investigated the origin of the optical bistability. The measured optical bistabilities revealed excellent hysteresis characteristics. The shift of the on-off position of the optical bistability decreased with the composite film with a large third-order nonlinear optical susceptibility.

In this paper, we report on the third-order nonlinear optical properties of poly(3-hexylthiophene) (P3HT) thin films prepared using solution methods. The third-order optical susceptibilities χ(3)(-3ω;ω,ω,ω) of P3HT thin films spin-coated and drop-cast on quartz glass substrates were estimated from optical third harmonics measured using the Maker-fringe method. The orientation, alignment, and crystallinity of the P3HT thin films obtained were evaluated using atomic force microscopy (AFM), X-ray diffraction (XRD) analysis, and UV–visible absorption spectra. The maximum nonlinear optical susceptibility χ(3) (NLOS), as estimated from the drop-cast film, was 1.55×10-8 esu, which was higher than that of a spin-coated film by one order. The enhancement of χ(3) is associated with the orientation and crystallinity of the P3HT molecule on the substrate.

Regioregular poly(3-hexylthiophene) [RR-P3HT] thin films were prepared on fused quartz glasses by spin-coating and drop-casting from the chloroform solutions. The effect of surface modification of quartz glass by hexamethyldisilazane (HMDS) on the RR-P3HT film structures was investigated. Film structures and morphologies were characterized by UV-visible absorption spectra, out-of-plane X-ray diffraction (XRD) and atomic force microscopy (AFM). The third-order nonlinear optical (NLO) susceptibilities Χ(3)(-3ω; ω, ω, ω) of the RR-P3HT films were determined by the third harmonic generation (THG) technique with an incident wavelength of 1064 nm. The drop-cast film shows enhanced Χ(3) of about three times of that of the spin-coated one, and HMDS treatment can increase the Χ(3) further to about 30 percent higher than the untreated one, keeping all the film thicknesses around 140 nm These results revealed the deposition method and surface modification effects on the RR-P3HT film structures, and the importance of higher ordering (enhanced inter-molecular interactions through π-π stacking) and increased crystallinity to the enhancement of the Χ(3) of the polymeric films for their applications in NLO devices.

In the present work, Poly(3-hexylthiophene)/Polymethylmethacrylate [P3HT/PMMA] composite thin film was prepared using spin coating method on the top of triangular prism as composing a prism coupling waveguide. The optical bistable characteristics of prism coupling waveguide comprising with P3HT/PMMA composite film was measured for different input laser power intensity using optical bistable measuring equipment. Also the effect of organic gas treatment on the optical bistable behavior of P3HT/PMMA quasi-waveguide has been investigated. The measured optical bistabilities have excellent stability and hysteresis characteristics. In the input laser power dependence of optical bistability, the on-off position shifts with the increase of input laser power intensity. A Nd:YAG laser with a wavelength of 1064 nm, a pulse width of 5 ns and a repetition frequency of 10 Hz was used for this measurement.

Vanadyl-phthalocyanine (VOPc) thin films deposited on a KBr substrate by molecular beam epitaxy (MBE) consist of nano-VOPc crystals epitaxially grown. The nano-VOPc crystals acquire a square shape as a result of annealing at 150°C. The size of the nano-crystals is controllable by changing the conditions of MBE deposition and thermal treatment. The growth processes of nano-crystals on the KBr substrate are elucidated experimentally and are shown to be closely related to strong interaction between the VOPc molecules and the KBr substrate. Their mechanisms can be explained in terms of surface diffusion of the VOPc molecules on the KBr substrate. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 163(2): 41–48, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20645

Organic field-effect transistors (OFETs) with water-soluble and crosslinkable poly(vinyl alcohol) (PVA) as a gate insulator and poly(3-hexylthiophene) (P3HT) as an active semiconductor were fabricated, and the device performances were investigated. Heat-crosslinked PVA displays better dielectric properties because it contains less water and the OFETs show enhanced on/off ratios and improved stability. P3HT films were fabricated by spin-coating and drop-casting methods and characterized by atomic force microscopy (AFM) and UV–visible absorption spectra. The mobilities of drop-cast P3HT films are one order higher than those of the spin-coated films, which is ascribed to the slower drying of the solvent and more-ordered structure in the films. However, OFETs with drop-cast P3HT show inferior saturation characteristics and lower on/off ratios. This is probably due to higher roughness and thickness of the drop-cast film and nonnegligible carrier transportation in the bulk, which can be demonstrated by the conductance measurements.

The organic thin film solar cells (OTFSCs) have been successfully fabricated using PCDTBT : PC71BM with different mixing ratios (1 : 1 to 1 : 8) and the influence of hole transport layer thickness (PEDOT : PSS). The active layers with different mixing ratios of PCDTBT : PC71BM have been fabricated using o-dichlorobenzene (o-DCB). The surface morphology of the active layers and PEDOT : PSS layer with different thicknesses were characterized by AFM analysis. Here, we report that the OTFSCs with high performance have been optimized with 1 : 4 ratios of PCDTBT : PC71BM. The power conversion efficiency (PCE = 5.17%) of the solar cells was significantly improved by changing thickness of PEDOT : PSS layer. The thickness of the PEDOT : PSS layer was found to be of significant importance; the thickness of the PEDOT : PSS layer at 45 nm (higher spin speed 5000 rpm) shows higher short circuit current density (Jsc) and lower series resistance (Rs) and higher PCE.

Highly oriented Vanadyl-Phthalocyanine (VOPc) thin film fabricated on Au (111) substrate has recently been attracting much attention in the fields of nanoelectronics and optoelectronics. Orientation control of VOPc thin film prepared on Au (111) substrate was performed by annealing treatment. The deposition process of VOPc thin film fabricated on Au (111) substrate involves three different phases. The initial deposition layer is epitaxially grown on Au (111), the next layer is the quasiepitaxial layer (pseudomorphic layer) and the final layer is the monoclinic layer (bulk layer). The quasiepitaxial layer treated with annealing transforms from the quasiepitaxial layer to the epitaxial layer. However, the morphology of the monoclinic layer is not changed by the annealing treatment.

Orientation control of vanadylphthalocyanine (VOPc) thin films deposited with different thicknesses on Pt (111) substrate were investigated by Vis/UV spectra measured by Vis/UV spectroscopy, XRD profiles analyzed by X-ray diffractometry (XRD), XPS spectra analyzed by a X-ray photoelectron spectroscopy (XPS) and AFM images observed using an atomic force microscope. The orientation of VOPc molecules deposited on a Pt (111) single crystal substrate is influenced by the oxidization on the surface of Pt (111) single crystal substrate, and the interaction between VOPc molecules and the surface of substrate is weak. Therefore, the interaction between VOPc molecules and the surface of substrate is only Van der Waals force.

The host-guest thin film using nonlinear optical material was fabricated by the spin coat method on the bottom face of a right-angled prism dropped down the solution of tershari-Butyl Vanadyl-phthalocyanine ((t-Bu)nVOPc) and PMMA. To improve the nonlinear optical characteristics, the host-guest thin film was treated with organic gas. Optical bistable characteristics were evaluated by using the optical quasi-waveguide prepared with host-guest thin film after and before organic gas treatment. After and before organic gas treatment, optical bistable characteristics were observed by changing the incident angles of laser beam to prism. Optical bistable characteristics after organic gas treatment were compared with before treatment. After treatment, optical bistable behavior is more sensitive than that before treatment. Moreover, the organic gas treating time dependences of optical bistability were investigated by using the measuring equipment of optical bistability.

Vanadyl-phthalocyanine (VOPc) thin films were prepared on two kinds of substrates by molecular beam epitaxy (MBE). Their characterization was carried out by scanning electron microscopy (SEM), reflection high-energy diffraction (RHEED) and atomic force microscopy (AFM). The desorption energy and mean residence time of VOPc molecules deposited on two kinds of substrates were also investigated using a Vis/UV spectroscope. The relationship between the morphology of VOPc thin film and the desorption energy of VOPc molecules deposited was discussed.

Orientation control of vanadylphthalocyanine (VOPc) thin films deposited on Au (111) substrate and Au substrate deposited on a microslide glass was studied with Vis/UV spectra, XRD profiles, XPS spectra and AFM images. Some of the VOPc molecules deposited on the Au substrate evaporated on the microslide glass epitaxially grow with the increase of substrate temperature during evaporating and it preheated before evaporating but others are inclined on the substrate. On the other hand, the VOPc thin film deposited on Au (111) substrate epitaxially grow with the increase of substrate temperature and it preheated. These are explained in terms of VOPc molecular diffusion on the substrate, the interaction between VOPc molecule and Au (111) substrate surface and the image force between the V-0 dipole and Au (111) substrate surface.

Vanadyl-phthalocyanine (VOPc) thick films were prepared by an organic molecular beam deposition (OMBD) method on KBr substrate. The morphologies and nonlinear optical properties of VOPc films were investigated with VIS/UV spectra, the incident angle dependence of third harmonic (TH) intensity measured by Marker fringe, SEM, and AFM images. The morphology of VOPc thick film prepared at the substrate temperature of 200°C is a pseudoepitaxy. Cracks and wrinkly parts on the film surface are observed from SEM and AFM images. The VOPc thick film exposed for 25 and 50hrs to 1.8 atm organic gas changes from pseudoepitaxy to epitaxy. Cracks and wrinkly parts on the film surface disappear due to the molecular diffusion during the gas treatment. It depends upon time exposed in organic gas. A VOPc thick film treated for 75hrs in 1.8 atm organic gas almost perfectly changes from pseudoepitaxy to epitaxy because it is impregnated with organic gas.

Vanadyl-Phthalocyanine (VOPc) thin films are prepared by a molecular beam epitaxy on KCl substrate. The nonlinear optical properties, VOPc molecular orientation and growing mechanism on KCl substrate of VOPc thin film are investigated with UV/VIS spectra, the images observed by SEM and AFM and the second-order harmonic (SH) and third-order harmonic (TH) intensities measured by Maker-fringe. The VOPc thin film treated with a thermal treatment changes from pseudo-epitaxy to epitaxy. Moreover, the surface of the thin film is a plate-like-crystal and smooth. These suggest that the VOPc molecules on KCl substrate are parallel to KCl substrate. The SH and TH intensities of VOPc thin films are increased with thermal treatment. It is closely related to the phase-morpholpgy of VOPc thin film. Therefore, the VOPc thin film epitaxially grown improves the SH and TH intensities.

Vanadyl phthalocyanine (VOPc) crystal thin films were prepared on poly(ethylene terephthalate) (PET) film. The VOPc film prepared on PET substrate at 120 °C had Phase II. The third harmonic (TH) intensity of the VOPc film was measured by the marker fringe method. The third optical susceptibility (χ(3)) estimated from TH intensity is 3.5 × 10−9 esu. The transition from Phase I to Phase II of the VOPc film was enhanced with corona charging. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 140(2): 36–43, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10022

Poly(3-octylthiophene)/Polymethylmethacrylate (P3OT/PMMA) composite waveguides were prepared by spin coating method as composing a prism-coupling waveguide. The UV-vis spectrum of P3OT/PMMA thin film was recorded in the range 300-900 nm using spectrophotometer to determine the optical absorption property of the composite thin film. The prepared P3OT/PMMA waveguide was treated with organic gas for 25 hrs to smoothing the surface of the thin film. An Nd: YAG laser with a wavelength of 1064 nm, a pulse width of 5 ns and a repetition frequency of 10 Hz was used for optical bistability measurement. The optical bistable characteristics of prism coupling waveguide comprising with P3OT/PMMA composite thin film was measured for different laser power intensities using optical bistable measuring equipment. The measured optical bistability displaced good stability and hysteresis characteristics. The input power dependence of optical bistability was observed and the switching on-off position shifted with the increase of input power intensity. In addition, the effects of organic gas treatment on the optical bistability of P3OT/PMMA composite waveguides were analyzed.

Vanadyl-phthalocyanine (VOPc) thin films were prepared on Polyethylene-terephthalate (PET) substrate by a molecular beam epitaxy (MBE). Dependence of morphologies and nonlinear optical properties of the VOPc films on preparing conditions was investigated using UV/VIS spectroscopy and third harmonic generation measurements. VOPc films prepared on the substrate of different temperatures (60°C120°C) showed two structures of a phase I and phase II. We suggested that the threshold temperature for structure changing from phase I to phase II existed at the vicinity of 80°C and also indicated that the TH intensity of VOPc thin film having phase II was more larger than that having phase I.

An organic field-effect transistor (OFET) was prepared with thin film fabricated by soluble pentacene as the semiconductor layer, polyimide thin film as the gate insulating layer, and Au as the drain, source and gate electrodes. The pentacene and polyimide thin films were fabricated by the cast and spin coat methods. The carrier mobility of the organic field-effect transistor was 1.2×10-2 cm2/Vs. The ON/OFF ratio was 3×102. As compared with the carrier mobility of OFET prepared by the evaporation method, their values were the same as that of the spin-coating method. However, the ON/OFF ratio obtained was lower. This indicates that it is either the leakage current in polyimide thin film that is large or it is that of the off-current of the pentacene thin film.

Vanadyl-phthalocyanine (VOPc) single crystals were prepared on KBr (1 0 0) substrate by molecular beam epitaxy (MBE). The second and third-harmonic generations of nonlinear optical thin films are proportional to the square of the thickness. Therefore, it is important to prepare a large nonlinear optical single crystal. However, the conditions to prepare a large nonlinear optical single crystal are not well understood yet. In this paper, we succeeded to prepare a large nonlinear single crystal. It was obtained with the control of substrate temp., evap. time and annealing time. The orientation and nonlinear property of VOPc single crystal prepared by the MBE method were also studied. The size of maximum single crystal prepared on KBr is 4×9×0.16 μm. The absorption spectrum of sample has an absorption peak at 790 nm. It reveals that the growth of single crystal gradually grow to a large crystal merging small crystals and also suggest that the VOPc single crystal is monoclinically grown from the results of RHEED pattern and UV/VIS spectrum. We estimated the third-order nonlinear optical susceptibility χ (3) from the TH intensity for VOPc single crystal monoclinically grown on KBr. Its χ (3) value estimated is 8.5×10 −10 esu. The value is 3 times higher than the value reported recently.

Vanadyl-phthalocyanine (VOPc) films were prepared on KBr substrate by MBE. They were characterized with RHEED, optical absorption spectra in visible and infrared regions (UV/VIS) and SEM. The thickness of prepared films is above 100 nm. The second and third harmonic generations (SHG and THG) of films were also measured by a Maker fringe method using a Nd·YAG laser. From these results, it was concluded that films are epitaxy films. We also estimated that the SH intensity of VOPc films are about 20 times higher than that of a Y cut quartz crystal and the third-order susceptibility χ(3) of VOPc film is about 3 times greater than the value reported recently by Fang et al.

We report the characterization and comparison of organic field-effect transistors (OFETs) based on vapor-deposited pentacene and a soluble pentacene precursor 13,6-N-Sulfinylacetamidopentacene in solution. The gate insulator, poly (4-vinylphenol) (PVP), was crosslinked by heat or UV irradiation. Spin-coated pentacene precursor film changed to pentacene film after heating in vacuum or nitrogen; and the film structure was characterized by the UV-visible absorption spectra and X-ray diffraction (XRD). Results show that the film structure of heated pentacene precursor is similar to that of the vapor-deposited pentacene but not exactly the same. Soluble pentacene precursor shows easier processability for fabrication of high-performance solution-processable OFETs. The determined carrier mobility for vapor-deposited pentacene film is in the order of 10-1 cm2/Vs, and for soluble pentacene precursor is in the order of 10-2 cm2/Vs.