Applied Mechanics and Materials Vol. 311

Abstract: Small molecule organic solar cell with an optimized structure of indium tin oxide (ITO)/copper phthalocyanine (CuPc) (10nm)/CuPc: C₆₀ mixed (20nm)/fullerene (C₆₀) (20nm)/bathocuproine (BCP) (10nm)/Al) was fabricated. With optimizing the hybrid planar-mixed molecular heterojunction (PM-HJ) from the double layer heterojunction (HJ) and the bulk heterojunction (BHJ), the short-circuit current density (J_sc) increased from 3.09 to 5.11mA/cm2, the open-circuit voltage (Voc) increased from 0.40 to 0.47V, and the power conversion efficiency (η_p) increased from 0.66 to 1.28% under 100mW/cm2 AM1.5G illumination. These improvements were attributed to reach the optimal balance among the light absorption efficiency, the exciton dissociation efficiency and the carrier collection efficiency of the device, resulting in enhancement of J_sc without affecting the value of fill factor (FF) and the reduction of the dark current. Furthermore a decrease of dark current is caused to the higher V_oc.

Abstract: A blue organic light-emitting diode (OLED) with a double hole-transporting (DHT) structure has been developed. The blue color purity was improved by modulation the thickness of CBP layer. When the thicknesses of left CBP and right CBP are respectively 8 nm and 2 nm, the more pure blue coordinates are (0.155, 0.079), which are very close to the blue coordinates of the national television system committee (NTSC) standard (0.14, 0.08). Furthermore the current density, brightness and the luminous efficiency of device with the left CBP of 8 nm and the right CBP of 2 nm are respectively 144.7 mA/cm2, 1065 cd/m2 and 0.93 cd/A.

Abstract: The cubic and rod-shaped powders of indium tin oxide were synthesized at a stable temperature reaction for 18h using the surfactant aid hydrothermal method under various conditions. The cubic and rod-shaped powder size changes with the concentration of the precursor. The finished products of indium tin oxide can be obtained by calcination at 500°C for 2h in air. Characterization was conducted using scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), X-ray diffractometry (XRD), thermogravimetric analyzer/differential thermal analysis (TG/DTA) and the Brunauer-Emmett-Teller (BET). XRD analysis shows that the conditions of this experiment can produce pure ITO powders. The characterization of cubic and rod-shaped ITO powders is also discussed.

Abstract: In this study, nano-crystallized TiO₂ photoelectrodes prepared by doctor-blade method on ITO-PEN substrate applied on flexible tandem dye sensitized solar cells (DSSCs) have been investigated by field emission scanning electron microscopy (FE-SEM), UV-Vis spectrophotometer (UV-Vis), and I-V characteristics analyses. In the analysis of FE-SEM, TiO₂ thin films prepared by doctor-blade method have the porous structure. The analyses of UV-Vis show that N3 and black dye could be adsorbed on the TiO₂ thin films, and the absorption wavelength of TiO₂ photoelectrodes could be obviously promoted from the ultraviolet ray to the visible light scope with N3 and Black dye adsorbed. It is great help for conversion efficiency of DSSCs. Under the irradiation of the sunlight simulator (AM 1.5,100 mW/cm²), the flexible dye-sensitized solar cell with double sensitized layers has the best conversion efficiency η =5.59 %.

Abstract: Antidot arrays of various diameters were patterned in permalloy thin films to explore their magnetic behavior. Porous anodic alumina had been used as a template to fabricate magnetic films with antidot array. Permalloy had been fabricated by depositing Ni₈₀Fe₂₀ onto anodic alumina membrane templates. The film thickness was 30 and 40 nm and the diameters of antidot varied from 200 to 350 nm. The coercivity of the antidot arrays is greater than that of unpatterned films and shows weak dependence on antidot diameter. The increase of the pore diameter was suggested to enhance domain wall pinning. The coercivity reaches a maximum value for the antidot array with the smallest pore diameter and reduces to an almost constant value for the antidot arrays with larger pore diameters.

Abstract: In this study, the flexible dye-sensitized solar cell is fabricated by pressurization-transfer technique, which involves assembling TiO₂ films on ITO/PEN flexible substrates via high temperature sintering. During the experiment, we change not only the film thickness and structure of TiO₂ but also the dye of working electrodes. The surface morphology of TiO₂ films are examined by field emission scanning electron microscopy (FE-SEM). The analyses of UV-Vis show that N3 dye could be adsorbed on the TiO₂ thin films, and the TiO₂ thin film with scattering layer has better absorption than that of without scattering layer. The current-voltage of the DSSC is illuminated by the solar simulator whose incident light intensity was 1000 W/m². These results indicate that the best efficiency of flexible dye-sensitized solar cell with high-temperature sintering TiO₂ film and scattering layer is 6.13%.

Abstract: This paper is based on theoretical methods to study the computer simulation and analysis of the growth of semiconductor thin films. First, according to the traditional theory of thin-film growth, the relationship between the growth morphology and the physical parameters are discussed. Then, fractal theory has been applied to improve the diffusion-limited aggregation (DLA) model. And the simulations of the two-dimensional and three-dimensional thin-film growth are proposed. A computer program of the simulation of the thin-film growth is developed with help of MATLAB. Finally, the results of the simulation of the thin-film growth have been analyzed by the fractal dimension and multifractal spectra. The results of this paper can be applied to the dynamic simulation of nanometer thin-film growth, and an effective simulation tool is to provide the semiconductor process.

Abstract: A numerical investigation is conducted to understand the factors of influence on a pool boiling in a micro system. The nucleation activities within microlayer were captured clearly to provide details of phase change process. Boiling curve of water under ambient pressure at 1atm is obtained, numerically, which makes good agreements with several experimental results. The effects of ambient pressure, contact angle and surface roughness on heat transfer were also studied, systematically

Abstract: Hole drilling strain gage method is a semi-destructive measurement. The method is most commonly used to measure residual stresses. The relieved strains are measured around the drilled hole, and the residual stresses are estimated by the mechanical relationship between relieved strains and residual stresses as well calibration coefficients. The calibration coefficients indicate the relieved strains due to unit stresses within the hole depth. Finite element method is always used to determine the calibration coefficients, and the analytical model is based on the infinite plate. But the geometrical shape and size of cylindrical part are different from the infinite plate. The relieved strains around the drilled hole are different too. Finite element model of the cylindrical part is constructed to obtain the hole drilling calibration coefficients. The measurement of residual stresses in a cylindrical part subject to axial loading calculated by calibration coefficients of both infinite plate and cylindrical part model are compared to show the difference.

Abstract: The effects of isothermal aging and the thermal cycling loading on the shear toughness of different solder materials and ball sizes have been explored. The difference between shear toughness values of traditional Sn/37Pb eutectic solder ball joints and the lead free Sn/3.0Ag/0.5Cu solders are chosen for discussion. The experiment measurements under the ball shear test (BST) have been compared and studied for both solder joints. The fracture behaviors of the solder joints under the high temperature aging and thermal cycling testing are examined by scanning electron microscope (SEM). The variation of shear toughness of different ball joints reveals that the high temperature aging and thermal cyclic loading reduce the shear toughness significantly. The measured shear toughness values indicate that the Sn/3.0Ag/0.5Cu solder joints have better ductility for the joints undergoing the high temperature aging and the thermal cycle loadings. Based on the measured results, the better reliability for the Sn/3.0Ag/0.5Cu ball joints is expected, due to the aging and cycling load testing.