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Porous silicon based visible light photodetectors with the characteristic structures of Al/porous silicon/Si were developed by evaporating aluminum contact onto the top surface of porous silicon films to form metal-semiconductor-metal Schottky junctions. The spongy nanostructures of the porous silicon film were characterized with the scanning electron microscopy. The current-voltage characteristics, the biased voltage dependent photocurrents and the illumination intensity dependent photocurrents were measured for the Al/porous silicon/Si visible light photodetectors. It is found that the photocurrents as large as 4 mA/cm2 can be achieved for the porous silicon based visible light photodetectors under the normal illumination of one 500 W tungsten lamp

Metal-semiconductor Zn/ZnO core-shell structures are fabricated by a simple ultrasonic process of raw Zn particles in water. The crystal structure, morphologies and fluorescence of the Zn/ZnO core-shell particles are characterized with X-ray diffraction (XRD), scanning electronic microscopy (SEM) and fluorescence spectrophotometer. The XRD pattern confirms that the shells of the Zn/ZnO core-shell particles are composed of Wurtzite ZnO crystals. The SEM study clearly exhibits the formation of ZnO on the surface of Zn spheres. The room-temperature fluorescence spectra have been observed a strong ultraviolet (UV)-visible emission at 381 nm and a yellow-green deep-level emission at about 534 nm. It is noted that the very broad green emission at 510 nm appears in the ZnO crystals with increasing the content of ZnO shell on the surface of Zn spheres. Furthermore, a possible formed mechanism of ZnO shells on the Zn core is discussed.

Zn/ZnO core-shell structured composites were firstly synthesized by water-boiling method using induction cooker and electric cooker. The synthesized Zn/ZnO core-shell structures were characterized with X-ray diffraction (XRD), scanning electronic microscopy (SEM) and photoluminescence (PL) spectrophotometer, respectively. The XRD pattern confirms that the shells of the Zn/ZnO core-shell composites are composed of wurtzite ZnO crystals. Based on SEM analysis, the Zn/ZnO core-shell structures formed by intermittent boiling under induction cooker show a tendency for spherical morphology with stacked and bending ZnO shells while the ones formed by continuous boiling under electric cooker exhibit a spherical morphology with the irregular ZnO nanorods on the surface of Zn spheres, and the continuous boiling under electric cooker can promote the peeling and regeneration of ZnO shells on the surface of Zn cores. The PL spectra of the Zn/ZnO core-shell structures have been recorded at room temperature and observed two peaks around 379 nm and 538 nm. However, the defect emission is much stronger than the UV emission in the Zn/ZnO core-shell structures synthesized under electric cooker.

A polyvinyl alcohol (PVA) nanocomposite thin film embedded with zinc sulfide (ZnS) quantum dots was fabricated by a drop-casting method. The ZnS-embedded PVA films were characterized with polarized optical microscopy (POM), ultraviolet-visible (UV-vis) spectroscopy and photoluminescence (PL) spectroscopy. The POM study clearly exhibits the photo-elasticity effects of the ZnS/PVA film when stress is added. Optical absorption spectra showed strong red shift for the ZnS quantum dots in the PVA matrix. Room-temperature PL spectra demonstrated that the pure ZnS quantum dots show cyan emission at 517 nm while ZnS/PVA thin film gives off blue PL with a strong broad peak at 478 nm and a shoulder peak at 536 nm.

Porous silicon (PS) is usually prepared by means of the anodization under constant current density, and fabrication of PS is a key step towards the realization of all-silicon electronic devices. It is a general belief that the photoluminescent properties of electrochemically etched PS depend on the anodization current density. In this work, we electrochemically prepared a series of PS films in the electrolyte of hydrofluoric acid by varying anodizing current density in the range of 1-70 mA/cm2. In spite of the different anodizing current density, the peak wavelength of the photoluminescence spectrum of the electrochemically anodized PS does not depend on the anodization current density. SEM has been utilized to characterize the morphology of the prepared PS films, and the mechanism is discussed for the anodization current independent photoluminescence of PS.

Zinc sulfide (ZnS) quantum dots (QDs) were encapsulated in ultraviolet (UV)-curable sealant upon the UV irradiation of the 365 nm. The QDs-sealant films were characterized with scanning electron microscopy (SEM), UV-visible spectroscopy and photoluminescence (PL) spectroscopy. Based on SEM analysis, the QDs encapsulated in UV-cured sealant clearly exhibited the formation of different size aggregates with a strong chemical bondage between the QDs and sealant. Optical absorption spectra showed strong red-shift for the QDs encapsulated in the UV sealant due to the aggregates of the QD nanoparticles. Room-temperature PL spectra have demonstrated that the pure QDs showed green emission at 517 nm while QDs-sealant film gave off cyan-blue PL with a strong and broad peak at 485 nm. Our results have demonstrated that the PL efficiency of QDs encapsulated in UV sealant matrix is higher than that of the QDs or UV sealant due to passivation of surfaces.

Trivalent Eu and Dy ions co-doped amorphous strontium aluminate oxide (SrAl2O4:Eu3+Dy3+) were synthesized through solution combustion route. The phase of the synthesized compound was examined with the X-ray diffractometry. The photoluminescence spectra of the amorphous SrAl2O4:Eu3+Dy3+ has shown that the sharp blue emission of Dy3+ at 483 nm, the sharp yellow emission of Dy3+ at 570 nm and the sharp red emission of Eu3+ at 615 nm can be integrated into the broad blue background emission of the amorphous host. The results indicate that the amorphous SrAl2O4 host can provide good environment to tune the emission color for the SrAl2O4:Eu3+Dy3+.

The synthesis of ZnO nanocrystals is carried out in alkaline alcoholic solution of zinc acetate dihydrate by sol-gel method. Effects of thermal annealing in nitrogen on photoluminescence (PL) properties of the sol-gel derived ZnO nanocrystals were investigated by PL spectroscopy. With increasing annealing temperature in nitrogen, UV emissions of the ZnO nanocrystals red-shifted from 378 nm to 388 nm while deep-level luminescent bands ranging from 450 to 700 nm with three emission centers at about 502 nm, 538 nm and 602 nm are enhanced, and the green luminescent band gains its intensity at the expense of the yellow and orange luminescent bands. Our results have demonstrated that the origin yellow-green color PL was tuned towards the cyan color PL with increasing the thermal annealing temperature in nitrogen from 344 oC to 813 oC.

By the control of the reducing atmospheres in the one-pot combustion reactions, Eu2+, Eu3+ and Dy3+ co-activated strontium aluminate oxide were synthesized. X-ray diffraction confirmed the formation of monoclinic SrAl2O4 nanocrystals. The photoluminescence spectra of the phosphors were measured. It is found that three sharp emissions at 483, 570 and 615 nm were superimposed onto the broad green emission band at about 520 nm. The origins of the broad green luminescent band, the sharp blue at 483 nm, and sharp yellow emissions at 570 nm and the sharp red emissions at 615 nm can be attributed to the 4f65d1→4f7 transitions of Eu2+ ions, the 4F9/2→6H15/2 transition of Dy3+ ions, the 4F9/2→6H13/2 transition of Dy3+ ions, and the 5D0–7F2 transition of Eu3+ ions in the SrAl2O4 nanocrystals, respectively. The results indicate that the white light emitting phosphors are possible by tuning the relative molar percentages of Eu2+, Eu3+ and Dy3+ in the phosphors.

ZnO/porous silicon nanocomposites were fabricated by spin-coating the sol–gels of zinc acetate onto the top surface of porous silicon films. The photoluminescent properties of ZnO/porous silicon nanocomposites were investigated as a function of the concentration of zinc cations in the sol–gels. Characterizations with scanning electron microscopy, X-ray diffractometry and photospectroscopy indicated that ZnO nanocrystals were embedded into the spongy nanostructures of porous silicon after heat treatment at 245 °C for 20 min in air. The recorded photoluminescence exhibited that orange to green–blue emissions were achieved for the ZnO/porous silicon nanocomposites as the concentration of zinc cations in the sol–gels increased from 4 to 260 mM. The mechanisms on the tunability of the photoluminescence were discussed for the ZnO/porous silicon nanocomposites. Our results have demonstrated that the incorporation of green–blue phosphors into the porous matrix of porous silicon represents one endeavor to tune the photoluminescence of porous silicon across the visible spectral region.

With polarizing optical microscopy we have investigated the electro-optic properties of a nematic liquid crystal 4-n-pentyl-4′-cyanobipheny confined in the microchannels of porous silicon. Experimental study shows clearly that the liquid crystal molecules tend to align parallel to the direction of the pore columns in porous silicon. Schlieren textures with S = +1 and +2 disclinations were recorded. Our experimental investigations show that uniaxial alignment, the planar radial and the escaped radial configurations exist around the given microchannels of porous silicon.

A rod-like liquid crystal (LC) N,N-(terephthalaldehyde) bis (4-n-hexadecyloxyaniline) (TBO16A) was synthesized and investigated by nuclear magnetic resonance (NMR), fourier transform infrared (FTIR), differential scanning calorimetry (DSC), polarizing optical microscopy (POM) and ultraviolet-visible (UV-vis) spectrophotometry. The FTIR,1H NMR and UV-vis absorption data confirmed the molecular structure of TBO16A. Our results demonstrated that the TBO16A can form enantiotropic smectic A phase.

The effect of sodium chloride on the sol-gel synthesized silica colloidal particles has been investigated. The silica colloidal particles in the size range of 420-800 nm were synthesized from the hydrolysis and condensation of tetraethyl orthosilicate by varying the amount of sodium chloride from 15 to 30 mg while keeping the tetraethyl orthosilicate (20 ml), ethanol (125 ml), ammonia (6 ml) and distilled water (18 ml) fixed. Scanning electron microscopy (SEM) was employed to analyze the morphology of the synthesized silica particles. Our results demonstrated that: (1) sticky and spongy silica spheroids were resulted if the amount of sodium chloride was less than 15 mg; (2) spherical silica particles were resulted with good monodispersity when the amount of sodium chloride was in the range of 22-24 mg; and (3) silica spheres were obtained but with a wide size distribution when the amount of sodium chloride was more than 26 mg.

Rod-like liquid crystals N-(4-methoxybenzylidene)-4-n-alkoxybenzenamine (MBnBA,n= 1, 2, 10) were synthesized and then were investigated by differential scanning calorimetry, polarizing optical microscopy, ultraviolet-visible spectrophotometry and fluorescence spectroscopy. Our results demonstrated that the dilute tetrahydrofuran solutions of each member in the family of MBnBA could give off blue fluorescence under the 325 nm excitation. The calculated electronic structures revealed that the fluorescence recorded at 469 nm (2.65 eV) was the result ofπ* →ntransitions in the molecules of the synthesized liquid crystals MBnBA.

A rod-like liquid crystal (LC) N,N-(terephthalylidene) bis (4-n-butylaniline) (TB4A) was synthesized by one step at room temperature. The synthesized TB4A were investigated with nuclear magnetic resonance, fourier transform infrared spectrometer and ultraviolet-visible spectrophotometry, differential scanning calorimetry and polarizing optical microscopy. Our results demonstrated that the TB4A can form nematic, smectic A, smectic C, smectic F and smectic G LC phases.

A liquid crystal (LC) N,N-(terephthalylidene) bis (4-octyloxyaniline) (TBO10A) was synthesized at room temperature. The LC TBO10A were investigated by differential scanning calorimetry (DSC), polarizing optical microscopy (POM), ultraviolet-visible spectrophotometry, photoluminecence (PL) spectroscopy and electronic structure calculations. In tetrahydrofuran solutions, two optical absorption bands were recorded for TBO10A at about 298 and 379 nm, respectively. Under the 325 nm excitation, dilute tetrahydrofuran solutions of the TBO10A can give off weak blue PL. With Hückel tight-binding method, the electronic structures of the TBO10A were calculated. Our results demonstrated that two absorptions can be attributed to theπ→π* andn→π* transitions in the rigid core of the TBO10A while the PL observed at about 481 nm (2.58 eV) can be assigned to theπ* →ntransition.

A typical liquid crystal (LC) N,N-(terephthalylidene) bis (4-decylbenzenamine) (TB10A) was firstly synthesized at room temperature. The synthesized LC TB10A were investigated by differential scanning calorimetry (DSC), polarizing optical microscopy (POM), ultraviolet-visible (UV-vis) spectrophotometry, photoluminecence (PL) spectroscopy and electronic structure calculations. Upon the 325 nm excitation, the dilute tetrahydrofuran solutions of TB10A could give off blue PL. With Hückel tight-binding method, the electronic structures of the TB10A were calculated. Our results demonstrated that the deep-blue PL observed at about 489 nm (2.54 eV) can be assigned to theπ* →ntransition for the TB10A.

Electrochemical deposition of copper from copper chloride aqueous electrolyte on porous silicon (PS) substrate was investigated in the current density range of 5 mA/cm2to 35 mA/cm2. Scanning electron microscopy (SEM) was utilized to characterize the surface morphology of as-electrodeposited PS. SEM images illustrate that the applied current density has a profound influence on the shape of copper crystal electrodeposited on the top surface of PS films. When the applied current density was fixed at 5mA/cm2, most of the copper crystals are in the shape of cube along with a small number of cuboid-shape. With the increasing current density, cuboid-shaped copper crystals gradually vanished. When the current density is up to the 35mA/cm2, we surprisingly observe that the cube shape predominates simultaneously with the emergence of truncated tetrahedron. A tentative explanation for the growth mechanism of copper crystal having various shapes is explored.

On the basis of the photoluminescence spectra, a spectrophotometric methodology is developed to determine the color coordinates of luminescent materials such as the red light-emitting porous silicon film, the green light-emitting aluminate-based phosphor and the blue light-emitting liquid crystal.

Soluble polypyrrole was obtained by naturally oxidizing pyrrole in air at room temperature for one to four years. Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy and ultraviolet-visible absorption spectroscopy were employed to characterize the chemical structures of the naturally oxidized polypyrrole. The electroluminescence from the naturally oxidized polypyrrole was recorded. The electroluminescence of the naturally oxidized polypyrrole was broad with its peak located at about 480 nm. Prototyped thin-film display panels were developed using the naturally oxidized polypyrrole as active medium.

Cobblestone-like CoSb3 nanoparticle films have been achieved via a catalyst-free vapor transport growth technique. The thermoelectric properties of the nanoparticle films were measured from room temperature to around 500 oC. The resultant CoSb3 nanoparticle films show high electrical conductivities due to clean particle surfaces. A maximum power factor reaches 1.848×10−4 W/mK2 at 440 oC. The discussed approach is promising for realizing new types of highly efficient thermoelectric semiconductors.

The photoluminescence (PL) of porous silicon films has been investigated as a function of the amount of liquid crystal molecules that are infiltrated into the constricted geometry of the porous silicon films. A typical nematic liquid crystal 4-pentyl-4′-cyanobiphenyl was employed in our experiment as the filler to modify the PL of porous silicon. It is found that the originally red PL of porous silicon films can be tuned to blue by simply adjusting the amount of liquid crystal molecules in the microchannels of the porous films. The chromaticity coordinates are calculated for the recorded PL spectra. The mechanism of the tunable PL is discussed. Our results have demonstrated that the luminescent properties of porous silicon films can be efficiently tuned by liquid crystal infiltration.

The transmittance spectra of one-dimensional photonic crystals (1-D PCs) with single defect in different location have been calculated. Defined the parameter N as the number of the layers located to the left of the single defect, set 13 as the number of the total layers of the 1-D PCs included the defect, during the course of the number of N increased from 0 to 12, as it upped to 3, there occurred defect band gap in the stop band gap, and when N upped to 12, the defect band gap disappeared; besides, the defect band gap is at frequencies between 0.3000~0.3090, most of them are at the frequencies around 0.3020. In addition, the transmittance has a turning point at the parameter N=7, that is to say, there has an approximate symmetry in transmittance when the parameter N increased from 3 to 11.

A novel linear conjugated polymer, poly(cyclopenta-1,3-diene), is designed. The electronic structures of poly(cyclopenta-1,3-diene) is calculated with extended Hückel tight binding program. The calculated band gap of the polymer is about 1.1 eV, which suggests this kind of conjugated polymer can be used in infrared optoelectronic devices.

Polymer dispersed liquid crystal (PDLC) devices were prepared by the method of polymerization induced phase separation. The transmittances and textures of the PDLC devices in OFF state and ON state were characterized by an ultraviolet-visible spectrometer and a polarized optical microscope, respectively. Our results demonstrated that the transmittances of our PDLC devices can be up to 95% when it is in ON state and that the transmittances of our PDLC devices is only about 20% when it is in OFF state.

Fractal features of branch-like structures grown from isotropic melt of a cholesterol liquid crystal were investigated with differential scanning calorimetry, polarized optical microscope and computer-aided simulation, respectively. With box-counting method, we have calculated the fractal dimension to be about 2.558-2.604 for the branch-like aggregates. Our growth simulation and the calculated value of the fractal dimension suggests that the cluster-cluster aggregation model can be applied to the growing processes of branch-like structures from isotropic melt of a cholesterol liquid crystal.

The effects of dopant 5-sulfosalicylic acid on the conductivity of polypyrrole were investigated. Under the condition of fixed molar ratio of oxidant-to-monomer (0.75: 1.00), a dozen of polypyrrole samples were made from chemical polymerizing the monomer pyrrole in aqueous medium by varying the dopant-to-monomer molar ratio. It was found that the dopant affected the conductivity and particle size of the synthesized polypyrrole. A maximum value for electrical conductivity of 5575 S/m was achieved when the molar ratio of dopant: oxidant: monomer is 2.25:0.75:1.00.

During the chemical synthesis nanometer-sized particles of ferrous iron oxide were in situ infiltrated into the mesopores in a porous silicon film. The microstructures of porous silicon and the magnetic properties of the nanometer-sized particles of the ferrous iron oxide were characterized with scanning electron microscopy, X-ray diffractometry, and the hysteresis loop measurement, respectively. Our results have demonstrated that the magnetic properties of the nanometer-sized Fe3O4 particles can be dramatically modified when they are confined into the mesopores of the porous silicon film.

We report here a series of polypyrrole/C60-H3PO4 two-layer photovoltaic cells fabricated by varying the C60 ratio with regard to polypyrrole. It is found that a slight amount of C60 can remarkably improve photovoltaic properties by four orders of magnitude; with C60 ratio the open-circuit voltage and short-circuit current increase, and at higher C60 ratio the photovoltaic working threshold is lowered too, the cell can even work efficiently in dark, more approaching the efficiency under strong illumination. The optimized device yields 1.2 V open-circuit voltage and 14 μA/cm2 short-circuit current, and a power conversion efficiency 0.01%. Our results show that polypyrrole is a potentially good material for photovoltaic cells. The effect of C60 in combination with polypyrrole is discussed.

Amphiphilic molecules self-assemble lamellar phase process in lyotropic liquid crystal formed by liquid dishwash was investigated with optical microscopy as concentration increases from its isotropic phase to its lamellar phase. We demonstrated that liquid dishwash molecules could assemble themselves into lamellar phase when their concentration increases between one pieces of glass substrate. We discussed the formative processes of Maltese-cross structure and phase transition from isotropic to lamellar phase.

A bent-core liquid crystal compound N,N-bis (4-propoxybenzylidene)benzene- 1,3-diamine was synthesized. Phase transition properties of the synthesized compound with the deferent heating rate were characterized with differential scanning calorimetry and polarized optical microscopy. , respectively. Our results demonstrated that the bent-core compound exhibited the completely undivided multi-phases in heating-rate ranges from 1oC/min to 6oC/min while it showed a broad-peak crystal phase in higher heating-rate ranges of 7-10oC/min for the first heating.

A series of long persistent phosphors Sr0.985-x Al2O4 : Eu2+0.015Dy3+x (X=0.000, 0.010, 0.020, 0.030, 0.040) were prepared through a combustion method at 600oC. We found that all the series of samples have good long afterglow properties by the naked eye. Then we use the laser to stimulate phosphors at 325nm, and their emission spectrums were tested by a spectrograph. We can found that the main emission peaks of all samples are all results from the 4f65d  4f7 (8S7/2) transition of Eu2+ instead of the 4f7 (6P7/2)  4f7 (8S7/2) transition of Eu2+ ions located about 515nm. In addition, the afterglow characteristic of all samples was investigated. Our results show that each decay curve consists of a rapid decay part followed by a long slow one and all samples have the same afterglow mechanism. And the Dy ions play an important role on the afterglow process.

We have investigated the photoluminescence (PL) of a porous silicon film in which a typical nematic liquid crystal 4-pentyl-4’-cyanobiphenyl infiltrated. Before the liquid crystal filtration, the PL spectrum of the porous silicon film is comprised of two luminescent bands, one of which is located at about 600 nm whereas the other of which is located at about 450 nm. After the liquid crystal filtration, the porous silicon film gives off intense deep-blue PL with its peak located at about 400 nm at the cost of the complete quenching of the PL from the original porous silicon film. Our results have demonstrated that the luminescent properties of porous silicon films can be dramatically modified by liquid crystal infiltration.

The model of the one-dimensional photonic crystals (1-D PCs) with a centered defect with increasing number of layers was considered, and characteristic matrix method was used to calculate the transmittance spectra of the 1-D PCs. From the transmittance spectra, it shown that during the course of the number N of the layers of 1-D PCs’ one side symmetrical increased from 2 to 16, there occurred defect band gap in the stop band gap, when N upped to 16 , the defect band gap disappeared; besides, the defect band gap is at the frequencies around 0.30. In addition, in the progress of N increased from 3 to 16, the defect band gap reduced from the frequency range 0.0570 to 0.00, and the transmittance declined from 73.59% to 13.94% in the defect band gap.

In this article, we report on the observations that in the aqueous electrolyte of aluminum nitrate, the thin metallic conducting films on both internal and external surface of porous silicon (PS) thin films that emit visible photoluminescence at room temperature prior to electrochemical deposition have been obtained under electrochemical deposition condition. Add to this high surface-to-volume ratio and these make it a good candidate for the catalyst supporter. We have investigated the surface morphology of PS after the interval of about 30 hours of electrochemically deposited aluminum by means of scanning electron microscopy (SEM). It has been shown from SEM images that not only micrometer-sized pores are smoothed by deposition of aluminum microcrystal, but also the presences of semi-sphere aluminum microcrystal which rooted in the tip of micrometer-sized pores are observed. On the one hand, this extremely interesting phenomenon which the micrometer-sized pores are smoothed may be explained in terms of principle of electrochemical deposition; on the other hand, we have laid the formation mechanism of semi-spherical aluminum microcrystal at the door of Gibbs free energy.

A series of long persistent phosphors Sr1-3x Al2O4 : Eu2+xDy3+2x (X=0.005, 0.010, 0.015, 0.020, 0.025)were prepared through a combustion method at 600oC. We found that all the series of samples have good long afterglow properties by the naked eye. Then we use the laser to stimulate phosphors at 325nm, and their emission spectrums were tested by a spectrograph. We can found that the emission peaks of all samples are all results from the 4f65d  4f7 (8S7/2) transition of Eu2+ instead of the 4f7 (6P7/2)  4f7 (8S7/2) transition of Eu2+ ions. In addition, the afterglow characteristic of the various samples and the same sample at different wavelengths was investigated. Our results show that each decay curve consists of a rapid decay part followed by a long slow one and all samples have the same afterglow mechanism.

By varying the antimony dopant level in the sol-gel solutions, we prepared a series of antimony-doped SnO2 films on slide glass with the sol-gel technique. The transmission, absorption, photoexcitation and photoemission spectra were measured for the sol-gel derived antimony-doped SnO2 films. Under the 300 nm excitation, near untraviolet emission at 390nm and blue emission at 460 nm were recorded from thermally annealed antimony-doped SnO2 films. The effect of the ionic dopant on the photoluminescent properties of the antimony-doped SnO2 films are discussed.

A series of cholesterol liquid crystal compounds was synthesized. Phase-transition temperatures and mesomorphic textures of these synthesized compounds were characterized with differential scanning calorimetry and polarized optical microscopy, respectively. In these molecules the terminal ester chains CnH2n-1COO-, where n was the number of carbon atoms in the terminal ester chains, were linked to the cholesterol core. All of the synthesized cholesterol compounds exhibited mesophases for the first heating. However, as temperature decreased from their clearing points, their micrographs can also be divided into two categories, the first category exhibits branch-like mesophase textures for n in the range of 1-10 while the second category exhibits branch-like crystal textures for n in the range of 11-18.

The primary aim of this communication is to introduce a novel approach of preparation of solar cell, viz. PS based solar cell, which is on the basis of the basic principle of the well established photovoltaic effect. We carefully investigate the current-voltage characteristics of the PS-based solar cell by virtue of performing the measurement of both current and voltage of PS-based solar cell under the condition of the sunlight irradiation and priori to sunlight irradiation in the purpose of observing clearly the photovoltaic effect possessed by the PS based solar cell. Judging by the results obtained in this paper, we can safely draw the conclusion that porous silicon is a good candidate material for the preparation of solar cell, that is to say that our study is giving high hope for the industrial production of high efficient PS-based thin film solar cells.

Polymer dispersed liquid crystal device was prepared by the method of polymerization induced phase separation. The phase separation in our PDLC device was characterized by a polarized optical microscope. Our results demonstrated that the phase-separated droplets in our PDLC device presented the four-brush radial, bipolar and axial configurations. Furthermore, these configurations were simulated by mathematica tool

The effects of dopant 5-sulfosalicylic acid on the conductivity of polypyrrole were investigated. Being nonhygroscopic, ammonium persulfate was used as the oxidant. Under the condition of fixed molar ratio of oxidant-to-monomer (0.375:1.00), a dozen of polypyrrole samples were made from chemical polymerizing the monomer pyrrole in aqueous medium by varying the dopant-to-monomer molar ratio. It was found that the dopant affected the conductivity and particle size of the synthesized polypyrrole. A maximum value for electrical conductivity of 5575 S/m was achieved when the molar ratio of dopant: oxidant: monomer is 2.25:0.375:1.00.

In this letter, characteristic matrix method was used to calculate the transmittance spectra of the one-dimensional photonic crystals (1-DPCs) with single defects in the center. From altering the refractive indexes n2’ and n3’ respectively for the defect, the transmittance spectra were calculated. From them, it shown that for the certain numerical value n3’=5.0, during the course of n2’ increased from 1.1 to 3.5, when it upped to 2.0, there occurred defect band gap in the stop band gap, and the defect band gap is at frequencies between 0.24~0.30. Besides, for n2’ =2.0, when n3’ increased from 1.1 to 3.5, there also occurred defect band gap in the stop band gap, and the defect band gap is at frequencies between 0.26~0.32. In addition, in these two progresses, the transmittance increased firstly and then decreased in the defect band gap.

The electronic structures of oligomers of pyrrole have been calculated using the extended Hückel tight-binding program. The energy diagrams are shown for oligomers as the number of the repeating unit in the oligomers increases from 1 to 16. The relationship between the energy gap of the oligomers and the number of the repeating unit in the oligomers is established. Blue-green photoluminescence and electroluminescence from one-dimensional polypyrrole are predicted.

Polymer dispersed liquid crystal film was prepared by the method of polymerization induced phase separation. The optical morphologies of the PDLC film were characterized by polarized optical microscope with a hot stage. Our results demonstrated that the morphology of the PDLC film depended on temperature of PDLC system.

By doping three complex dopants in different molar ratio, a series of polypyrroles doped with 9, 10-anthraquinone-2-sulfonic acid sodium, 5-sulfosalicylic acid and toluene-4-sulfonic acid were synthesized by polymerizing the monomer pyrrole in aqueous solution of ferric chloride. The resulting polypyrroles were characterized with the four-probe and laser light scattering, respectively. Our results indicate that optimized value of conductivity reached to 6683 S/m when the molar ratio of anthraquinone-2-sulfonic acid sodium to 5-sulfosalicylic acid to toluene-4-sulfonic acid was 2:1:3. For applications of polymer in optoelectronics, in lithium-ion battery and in electromagnetic shielding, to obtain optimized value of conductivity has great significance for us.

Characteristic matrix method was used to calculate the transmittance spectra of the one-dimensional photonic crystals (1-D PCs). By theoretical calculations, the transmittance spectra of time-harmonic electromagnetic wave in the 1-D PCs with various incident angles were derived. From the transmittance spectra, it shown that along with the incident angle increased from 0o to 85o, the frequency range of stop band gap also increased from 0.085 to 0.119 for the certain periodicity N=16 of the 1-D PCs. In addition, for a certain incident angle (in this letter, the incident angle 30o was used), the transmittance spectra for different periodicity (N=2, 4, 8 and 16 respectively) were also calculated, it demonstrated that different incident angles could influence the stop band gap range markedly, but on the transmittance was minimal.

A soluble polypyrrole without any substituent groups was obtained by controlling the oxidation level of polypyrrole in the presence of oxygen. Upon the exposure to the 325 nm ultraviolet excitation from a helium-cadmium laser, thin films of the non-substituted polypyrrole could give off strong photoluminescence with its peak at about 530 nm. To elucidate the origin of the recorded strong photoluminescence, we measured the absorption spectra of the polypyrrole thin films with ultraviolet-visible absorption spectroscopy and our data indicated the appropriately oxidized polypyrrole are free of polarons. With the help of the electronic structures calculated with Hückel tight-binding method, the intense photoluminescence is interpreted in terms of the direct electronic transitions from the conduction band to valence band of the conjugated polymer.

The optical absorption and photoluminescence (PL) of 5-(2-pyrrolyl)-2-pyrrolidinone were investigated with ultra-visible absorption spectroscopy and photoluminescence spectrscopy. Upon the 325 nm excitation from a helium-cadmium laser, strong blue PL was recorded for the 5-(2-pyrrolyl)-2-pyrrolidinone. The peak of the PL was located at about 425 nm (2.92 eV). The origin of the strong PL can be assigned to isolated carbonyl group.

In the present paper, we have not only investigated the top surface and cross-section morphology, but also measured photoluminescence spectra characteristic of porous silicon after deposition of metallic ions by electrochemical deposition employing scanning electron microscopy (SEM) and spectrometer, respectively. It is apparent from the SEM images that the microstructure of porous silicon is seriously ruined by the metallic ions deposited by electrochemical deposition. Most interesting is the finding that in the photoluminescence spectrum of porous silicon after the deposition of metallic ions such as AL3+ and Cu2+, the luminescence band gradually is quenched as the electrochemical deposition progressed. A careful consideration of the results obtained show that according to the basic theory of well-established quantum confinement model, the quenching of photoluminescence spectra of porous silicon may well be attributed to the microstructure fell into ruin. On the other side of the fence, we can interpret the physical origin of the phenomenon in view of the presence of metallic ions which give rise a series of energy level deep in the band gap of porous silicon.

A series of polypyrrole samples were synthesized by oxidizing pyrrole in the aqueous medium of ferric chloride, and the relation between oxidant/monomer ratio and the electrical conductivity of polypyrrole was studied by increasing the ratio from 0.25:1 to 2.5:1. Our results showed that the conductivity of polypyrrole was dependent on the mole ratio of the oxidant to pyrrole, and a maximum value for electrical conductivity of 1500 S/m was achieved for a ratio of 0.75:1.