Electrodeposition of Cu_2O/g-C_3N_4 heterojunction film on an FTO substrate for enhancing visible light photoelectrochemical water splitting

An immobilized Cu2O/g-C3N4 heterojunction film was successfully made on an FTO substrate by electrophoretic deposition of g-C3N4 on a Cu2O thin film.The photoelectrochemical（PEC） performance for water splitting by the Cu2O/g-C3N4 film was better than pure g-C3N4 and pure Cu2O film.Under-0.4 V external bias and visible light irradiation,the photocurrent density and PEC hydrogen evolution efficiency of the optimized Cu2O/g-C3N4 film was-1.38 mA/cm^2 and 0.48 mL h^-1 cm^-2,respectively.The enhanced PEC performance of Cu2O/g-C3N4 was attributed to the synergistic effect of light coupling and a matching energy band structure between g-C3N4 and Cu2O as well as the external bias.

Light Simplified Cultivation Techniques of Wide Row and Double Ridge with Filming, Fertilizing and Sowing on One for Foxtail Millet

In view of the problems of completely depending on rain, low and unstable yield and complicated planting of dry land foxtail millet, the light simplified cultivation techniques of wide row and double ridge with filming, fertilizing and sowing on one for foxtail millet was formed through the integration of plastic film mulching technology and mechanized production technology by Institute of Millet crops of Hebei Academy of Agriculture and Forestry Sciences, and the techniques were introduced from the key technologies of pre-sowing preparation, sowing, supporting equipment, field management, harvesting, plastic film recycling.

Review of blue perovskite light emitting diodes with optimization strategies for perovskite film and device structure

Perovskite light emitting diodes(PeLEDs)have attracted considerable research attention because of their external quantum efficiency(EQE)of>20%and have potential scope for further improvement.However,compared to red and green PeLEDs,blue PeLEDs have not been extensively investigated,which limits their commercial applications in the fields of luminance and full-color displays.In this review,blue-PeLED-related research is categorized by the composition of perovskite.The main challenges and corresponding optimization strategies for perovskite films are summarized.Next,the novel strategies for the design of device structures of blue PeLEDs are reviewed from the perspective of transport layers and interfacial layers.Accordingly,future directions for blue PeLEDs are discussed.This review can be a guideline for optimizing perovskite film and device structure of blue PeLEDs,thereby enhancing their development and application scope.

Experimental studies of extraordinary light transmission through periodic arrays of subwavelength square and rectangular holes in metal films

We fabricate a series of periodic arrays of subwavelength square and rectangular air holes on gold films, and measure the transmission spectra of these metallic nanostructures. By changing some geometrical and physical parameters, such as array period, air hole size and shape, and the incident light polarization, we verify that both global surface plasmon resonance and localized waveguide mode resonance are influential on enhancing the transmission of light through nanostructured metal films. These two resonances induce different behaviours of transmission peak shift. The transmission through the rectangular air-hole structures exhibits an obvious polarization effect dependent on the morphology. Numerical simulations are also made by a plane-wave transfer-matrix method and in good consistency with the experimental results.

Formation and Gas Barrier Characteristics of Polysilazane-Derived Silica Coatings Formed by Excimer Light Irradiation on PET Films with Vacuum Evaporated Silica Coatings

The effects of excimer light irradiation on polysilazane coatings formed on PET films with vacuum-evaporated SiO2 coatings and the effects of these coatings on gas barrier characteristics have been investigated. The temperature during light irradiation has a large effect on the coating’s molecular structure and gas barrier characteristics. When irradiation was performed at 100℃, the polysilazane coating transformed into a silica coating, and a compact silica coating at a much lower temperature than with heat treatment alone was produced. Surface irregularities in the vapor-deposited silica coating were smoothed out by the formation of a polysilazane coating, which was transformed into a compact silica coating when irradiated with light, resulting in a significant improvement in the gas barrier characteristics. The water vapor permeability of the thin coating irradiated with excimer light at 100℃ showed only 0.04 g/m2•day (40℃, 90% RH). According to the results of investigation of temperature variation of water-vapor permeability, it is inferred that the developed film has an excellent gas barrier value, namely, 4.90 × 10–4 g/m2•day at 25℃. This gas barrier coated PET film is transparent and flexible, and can be used in the fabrication of flexible electronics. Also, the proposed fabrication method effectively provides a simple low-cost and low-temperature fabrication technique without the need for high vacuum facility.

THE LIGHT INDUCED CHANGE IN TRANSIENT PHOTOCONDUC-TIVITY OF POLYMORPHOUS SILICON FILMS

The decays of transient photoconductivity and their light-induced changes of polymorphous silicon (pm-Si:H) films were investigated. The decays can be fit fairly well by a sum of two exponential decay functions, which indicates that there are two kinds of traps contributing to the process. The light-induced changes of the concentration and energy level of the traps were estimated. The results show that the light-induced changes in trap energy position Et, trap concentration Nt as well as photoconductivity are markedly less for pm-Si:H than that for a-Si:H.

Efficiency analysis of a-SiC:H thin film light emitting diodes

The hole injection,the radiative recombination and the device luminescent efficiencies of amorphous silicon carbide thin film p-i-n junction light emitting diodes are quantitatively calculated,and the effect of the carrier(especially the hole) injection and recombination processes on the device luminescent characteristics are revealed.Without considering the device junction temperature,it is found that the device luminescent efficiency mainly depends on the hole injection efficiency at low field and the hole radiative recombination efficiency at high field respectively.The theoretical analyses are in well agreement with the experimental results.

Development of Dual-light Path Monitoring System of Optical Thin-film Thickness

The accurate monitoring of optical thin-film thickness is a key technique for depositing optical thin-film. For existing coating equipments, which are low precision and automation level on monitoring thin-film thickness, a new photoelectric control and analysis system has been developed. In the new system, main techniques include a photoelectric system with dual-light path, a dual-lock-phase circuit system and a comprehensive digital processing-control-analysis system.The test results of new system show that the static and dynamic stabilities and the control precision of thin-film thickness are extremely increased. The standard deviation of thin-film thickness, which indicates the duplication of thin-film thickness monitoring, is equal to or less than 0.72%. The display resolution limit on reflectivity is 0.02 %. In the system, the linearity of drift is very high, and the static drift ratio approaches zero.

Light scattering of nanocrystalline TiO_2 film used in dye-sensitized solar cells

This paper studies the light scattering and adsorption of nanocrystalline TiO2 porous films used in dye-sensitized solar cells composed of anatase and/or rutile particles by using an optical four-flux radiative transfer model. These light properties are difficult to measure directly on the functioning solar cells and they can not be calculated easily from the first-principle computational or quantitative theoretical evaluations. These simulation results indicate that the light scattering of 1 25 nm TiO2 particles is negligible, but it is effective in the range of 80 and 180 nm. A suitable mixture of small particles （10 nm radius）, which are resulted in a large effective surface, and of larger particles （150 nm radius）, which are effective light scatterers, have the potential to enhance solar absorption significantly. The futile crystals have a larger refractive index and thus the light harvest of the mixtures of such larger rutile and relatively small anatase particles is improved in comparison with that of pure anatase films. The light absorption of the 10μm double-layered films is also examined. A maximal light absorption of double-layered film is gotten when the thickness of the first layer of 10 urn-sized anatase particles is comparable to that of the second larger rutile layer.

The Application of Lights-Conversed Polyethylene Film for Agriculture

Lanthanum-rhodamine (6G and B) complexes were synthesized by Rheological Phase Reaction Method. Lanthanum-rhodamine (6G and B) complexes doped polyethylene films which have a function of lights-conversion were prepared. The emission and excitation spectra were measured. The experiments of growing seedling and culture were carried out in the shed built with doped and undoped polyethylene films. Lanthanum-rhodamine doped polyethylene films which have a function of lights-conversion can efficiently convert the green light in the sunlight to the red light for photosynthesis of crops, to promote the maturing of crops and raise the yield of crops.

Characteristic improvements of thin film AlGaInP red light emitting diodes on a metallic substrate

We report a type of thin film Al Ga In P red light emitting diode（RLED） on a metallic substrate by electroplating copper（Cu） to eliminate the absorption of Ga As grown substrate.The fabrication of the thin film RLED is presented in detail.Almost no degradations of epilayers properties are observed after this substrate transferred process.Photoluminescence and electroluminescence are measured to investigate the luminous characteristics.The thin film RLED shows a significant enhancement of light output power（LOP） by improving the injection efficiency and light extraction efficiency compared with the reference RLED on the Ga As parent substrate.The LOPs are specifically enhanced by 73.5% and 142% at typical injections of 2 A/cm^2 and 35 A/cm^2 respectively from electroluminescence.Moreover,reduced forward voltages,stable peak wavelengths and full widths at half maximum are obtained with the injected current increasing.These characteristic improvements are due to the Cu substrate with great current spreading and the back reflection by bottom electrodes.The substrate transferred technology based on electroplating provides an optional way to prepare high-performance optoelectronic devices,especially for thin film types.

Tandem organic light-emitting diode with a molybdenum tri-oxide thin film interconnector layer

A 10-nm-thick molybdenum tri-oxide（MoO3） thin film was used as the interconnector layer in tandem organic lightemitting devices（OLEDs）.The tandem OLEDs with two identical emissive units consisting of N,N-bis（naphthalen-1-yl）N,N-bis（phenyl）-benzidine（NPB） /tris（8-hydroxyquinoline） aluminum（Alq3） exhibited current efficiency-current density characteristics superior to the conventional single-unit devices.At 20 mA/cm2,the current efficiency of the tandem OLEDs using the interconnector layers of MoO3 thin film was about 4.0 cd/A,which is about twice that of the corresponding conventional single-unit device（1.8cd/A）.The tandem OLED showed a higher power efficiency than the conventional single-unit device for luminance over 1200cd/m2.The experimental results demonstrated that a MoO3 thin film with a proper thickness can be used as an effective interconnector layer in tandem OLEDs.Such an interconnector layer can be easily fabricated by simple thermal evaporation,greatly simplifying the device processing and fabrication processes required by previously reported interconnector layers.A possible explanation was proposed for the carrier generation of the MoO3 interconnector layer.

Light scattering effect of submicro-textured Ag/Al composite films prepared at lower substrate temperatures

We present a new and practical approach for preparing submicro-textured silver and aluminum （Ag/Al） double-structured layers at low substrate temperatures. The surface texturing of silver and aluminum double-structured layers was performed by increasing the deposition temperature of the Al layers to 270℃. The highly submicro-textured silver and aluminum double-structured layers were prepared by thermal evaporation on quartz glasses and their surface microstructure, light scattering properties, and thermal stability were investigated. Results showed that the highly submicro-textured Ag/Al composite films prepared at low substrate temperatures used as back reflectors not only can enhance the light scattering and have good thermal stability, but also have good adhesion properties. In addition, their fabrication is low cost and readily carried out.

Fabrication and optical properties of InGaN/GaN multiple quantum well light emitting diodes with amorphous BaTiO_3 ferroelectric film

BaTiO3 （BTO） ferroelectric thin films are prepared by the sol,el method. The fabrication and the optical properties of an InGaN/GaN multiple quantum well light emitting diode （LED） with amorphous BTO ferroelectric thin film are studied. The photolumineseence （PL） of the BTO ferroelectric film is attributed to the structure. The ferroeleetric film which annealed at 673 K for 8 h has the better PL property. The peak width is about 30 nm from 580 nm to 610 nm, towards the yellow region. The mixed electroluminescence （EL） spectrum of InGaN/GaN multiple quantum well LED with 150-nm thick amorphous BTO ferroelectric thin film displays the blue-white light. The Commission Internationale De L＇Eclairage （CIE） coordinate of EL is （0.2139, 0.1627）. EL wavelength and intensity depends on the composition, microstructure and thickness of the ferroelectric thin film. The transmittance of amorphous BTO thin film is about 93% at a wavelength of 450 nm-470 nm. This means the amorphous ferroelectrie thin films can output more blue-ray and emission lights. In addition, the amorphous ferroelectric thin films can be directly fabricated without a binder and used at higher temperatures （200 ℃-400 ℃）. It is very favourable to simplify the preparation process and reduce the heat dissipation requirements of an LED. This provides a new way to study LEDs.

Nanometer Thick Diffused Hafnium and Titanium Oxide Light Sensing Film Structures

We examine 10 nm thick film structures containing either Hf or Ti sandwiched between two respective oxide layers. The layers are deposited onto heated substrates to create a diffusion region. We observe a high degree of light sensitivity of the electric current through the film thickness for one polarity of an applied voltage. For the other polarity, the current is not affected by the light. We explain the observed phenomenology using the single-particle model based on the existence of interface states on the metal-oxide interfaces.

Low Temperature DC Sputtering Deposition on Indium-Tin Oxide Film and Its Application to Inverted Top-emitting Organic Light-emitting Diodes

Indium tin oxide （ITO） ultrathin films were prepared on glass substrate by DC （direct current） magnetron sputtering technique with the assistance of H2O vapor to avoid potential surface damage. The film properties were characterized by X-ray diffraction （XRD） technique, four-point probe method and spectrophotometer. The results show that the deposited ITO film with introduced H2O during sputtering process was almost amorphous. The average visible light transmission of 100 nm ITO film was around 85% and square resistivity was below 80 Ω/square. The film was used as the transparent anode to fabricate an inverted top-emitting organic light-emitting diodes （IT-OLEDs） with the structure of glass substrate/Alq3 （40 nm）/NPB （15 nm）/CuPc （x nm）/ITO anode （100 nm）, where the film thickness of CuPc was optimized. It was found that the luminance of this IT-OLEDs was improved from 25 cd/m^2 to more than 527 cd/m^2 by increasing the thickness of CuPc, and luminance efficiency of 0.24 lm/W at 100 cd/m^2 was obtained, which indicated that the optimized thickness of CuPc layer was around 15 nm.

Light focusing in linear arranged symmetric nanoparticle trimer on metal film system

Benefiting from the induced image charge on film surface,the nanoparticle aggregating on metal exhibits interesting optical properties.In this work,a linear metal nanoparticle trimer on metal film system has been investigated to explore the novel optical phenomenon.Both the electric field and surface charge distributions demonstrate the light is focused on film greatly by the nanoparticles at two sides,which could be strongly modulated by the wavelength of incident light.And the influence of nanoparticle in middle on this light focusing ability has also been studied here,which is explained by the plasmon hybridization theory.Our finding about light focusing in nanoparticle aggregating on metal film not only enlarges the novel phenomenon of surface plasmon but also has great application prospect in the field of surface-enhanced spectra,surface catalysis,solar cells,water splitting,etc.

Heat-Resistant Properties of a SiO₂-Coated PET Film Prepared by Irradiating a Polysilazane-Coated Film with Excimer Light

Flexible electronics have been recently paid much attention. A flexible substrate (Organic resin film) is indispensable component for flexible devices. Though PET film is low-cost organic film, low heat-resistance of PET film limits its application as a flexible device substrate. We have developed heat-resistant PET which does not deteriorate even at 190°C heat treatment for one hour. An excimer light was irradiated onto a polysi-lazane (PHPS: perhydropolysilane)-coated film to form a dense silicon-dioxide (SiO2) layer on a PET film, and the heat-resistance property of the formed film was examined. Changes of surface state and cross-sectional structure of the formed film due to heat treatment were investigated by scanning electron microscope (SEM) and transmission electron microscope (TEM). Compared to normal PET, which is deteriorated and whitened by heat treatment of about 110°C - 120°C, the SiO2-coated PET film maintains transparency and does not deteriorate after heat treatment at 180°C - 190°C for one hour. This high heat resistance is due to a dense SiO2 film formed on the surface that prevents surface precipitation and crystallization of low-molecular-weight oligomers (which are the cause of thermal degradation of PET). It is expected that enhancing the heat resistance of PET—which has high versatility and low cost—to about 180°C to 190°C will allow SiO2-film-coated PET to be developed as a film substrate for flexible devices.

New Preparation Method of Visible Light Responsive Titanium Dioxide Photocatalytic Films

We report a new and simple preparation method of the visible light responsive Titanium dioxide (TiO2) photocatalytic films using sol-gel method and ultraviolet light (UV) irradiation. Proposed films were prepared on fused silica plates using titanium tetra-isopropoxide, urea, 2-methoxyethanol, water and UV irradiation. The 650°C-annealed films were carbon-containing anatase type TiO2, not carbon-doped ones. The prepared films absorbed visible light with wavelengths longer than 400 nm. Also, organic dyes were effectively photodegradated by visible light irradiation in the presence of these films.

Light-Induced Charge Transfer at Interface Between Lipid-Free RhTSPc Film and p-Si(111)

The present paper covers the lipid-free rhodium tetrasulfonato-phthalocyanine (RhTSPc) films prepared on p-Si(111) by using Langmuir-Blodgett technique. Their surface photovoltage spectra were measured. It was found that there is a strong interaction at the interface between the RhTSPc film and p-Si (111) and that the surface photovoltaic effect of the film system is maximum when only one monolayer of RhTSPc molecules coats p-Si(111), which is similar to that of CuTSPc films on p-Si(111) reported previously. These results confirm that only the monolayer of dye molecules being adjacent to the semiconductor surface plays a key role in the light-induced interfacial charge transfer process.