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We propose a new antireflection (AR) design for organic photovoltaics (OPVs) to achieve broadband and omnidirectional enhancement of photocurrent. In the proposed design, a hybrid AR structure, which combines moth eye texturing and two-layer interference coating, is integrated with a glass substrate having a high refractive index (n). Using the optical simulation for OPV cells, we compare the performance of various AR configurations upon changing the refractive index of the glass substrate. We show that the short-circuit current density ($$J_{SC}$$ JSC ) is decreased by using the high-nglass substrate without AR coating, whereas $$J_{SC}$$ JSC is significantly increased by applying the high-nglass substrate with the hybrid AR structure, suggesting an importance of the integrated design. In addition, we demonstrate that the proposed AR configuration is quite effective to attain broad angle performance and is robust against the variations in geometric features of moth eye texture. Finally, the spectral dependence of photocurrent generation is experimentally measured for the verification of the effectiveness of the integrated AR design. These results provide a practical and efficient AR technique that can further expand the potential of OPVs as energy supply devices.

The SiO2layer fabricated by the atomic layer deposition (ALD) method was applied to control the efficiency of the fluorescence quenching by graphene oxide (GO) in supported lipid bilayers (SLBs). SLB was formed by the vesicle fusion method on the ALD-SiO2layer on GO deposited on thermally oxidized SiO2/Si substrates. Wide-field fluorescence observation of SLB on ALD-SiO2layers with various thicknesses showed that the ALD-SiO2layer varied the efficiency of fluorescence quenching with reasonable distance dependence expected from the equation of Förster resonance energy transfer. Fluorescence single molecular observation of dye-labeled lipids was achieved in SLB existing in the effective range of the quenching by GO. Quenching experiment using Co2+that selectively quenches the fluorescence from the upper leaflet of SLB revealed the difference in the fluorescence intensity between the upper and lower leaflets of SLB due to their distance from GO.

To improve the power conversion efficacy of organic photovoltaics (OPVs), it is required to design antireflection structures that could realize efficient and broadband light trapping. In this article, we perform global optimization of the textured pattern of moth eye antireflection surfaces to maximize the short-circuit current density (JSC) of OPVs with a poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM)-based bulk heterojunction. We introduce an optimization algorithm consisting of two steps: in the first step, the simple grid search is conducted to roughly estimate a globally optimal solution, while in the second step, the Hooke and Jeeves pattern search is executed to refine the solution. By combining the optimization algorithm with the optical simulation based on the finite-difference time-domain method, we find the optimal period and height of moth eye array with which the level of JSCcan be increased by 9.05% in the P3HT:PCBM-based organic solar cell. We also demonstrate that the optimized moth eye structure can significantly modify the light path at a long wavelength range to strengthen the electric field intensity and enhance energy absorption within the active layer.

We propose a hybrid antireflection structure (ARS), which integrates moth eye texturing and multilayer interference coating, to improve efficiency of organic photovoltaic (OPV) solar cells. We perform nearly global optimization of the geometric parameters characterizing the hybrid ARS, by using optical simulations based on the finite-difference time-domain method. The proposed optimization algorithm consists of two steps: in the first step, only the moth eye structure is globally optimized and, in the second step, the whole hybrid structure is optimized efficiently based on the results of the first step. Thus, the optimal moth eye structure is additionally obtained as an intermediate result. By applying this optimization method to an organic thin film solar cell, we show that the short-circuit current density (JSC) is increased by 8.90% with the moth eye structure and by 9.89% with the hybrid ARS. We also study the sensitivity of photocurrent to the geometric parameters of hybrid ARS, and the change in the spatial distribution of electric field intensity by the ARS. The results show that the hybridization of the two types of light trapping techniques is effective to reduce the inhomogeneity in the electric field distribution and obtain higher electric intensity in almost the whole active layer. The design concept of the hybrid ARS is quite useful for improving light trapping in OPVs and allows for extending the options available for broadband antireflection.

Metal-organic chemical vapor deposition (MOCVD) method has been applied to grow nanostructured ZnO films on Si (100) substrate at temperatures ranging from 200 to 550 °C. The as-prepared films were characterized by XRD, SEM, XPS analysis. The growth rate of ZnO films increases with increasing the deposition temperatures. The deposition temperatures have a drastic effect on the crystallinity and morphology of the nanostructured ZnO. Whisker shaped ZnO is formed at a temperature of 350 °C. The deposition time also affects the morphology of the particles. At 400 °C, sample with one hour deposition forms whisker shaped ZnO nanostructures whereas that of with two hours deposition forms flower-like nanostructures.

Degradation of N719 dye on TiO2 electrodes in dye-sensitive solar cells with high temperatures up to 80degC and a visible light exposure were investigated using infrared absorption spectroscopy (IRAS) with a multiple-internal-reflection (MIR) technique. In this study, we developed an in situ observation technique to measure structural changes in the N719-dye molecule on the TiO2 electrode even with a liquid iodine electrolyte. MIR-IRAS clearly indicates the structural changes in the N719 dye molecule such as degradation of NCS groups and hydrocarbon. Water generation was also detected on the TiO2 surface. Guanidine isothiocyanate addition into the electrolyte prohibits the degradation of NCS with the light exposure and the high temperature treatment. The degradations of dye, electrolyte, and TiO2 electrode in the dye sensitized solar cells with the light exposure and thermal treatments are discussed in this paper.

We have successfully fabricated nickelsilicide-metalgate MOS capacitors at a low temperature of 280aC by treating poly Si stacked SiO2/Si substrates with a Cl plasma containing NiCl. We have confirmed atomically sharp NiSi/oxide interfaces after the present process where any interface segregation can not be observed by cross-sectional TEM measurements. The present process allows a control of Ni concentration in the gate metal film and the work function in the gate metal is adjustable in the range from 4.3 to 4.9 eV, which is suitable for the Si CMOS process.

Degradation of N719 dye on TiO2electrodes in dye-sensitive solar cells with high temperatures up to 80°C and a visible light exposure were investigated using infrared absorption spectroscopy (IRAS) with a multiple-internal-reflection (MIR) technique. In this study, we developed an in situ observation technique to measure structural changes in the N719-dye molecule on the TiO2electrode even with a liquid iodine electrolyte. MIR-IRAS clearly indicates the structural changes in the N719 dye molecule such as degradation of NCS groups and hydrocarbon. Water generation was also detected on the TiO2surface. Guanidine isothiocyanate addition into the electrolyte prohibits the degradation of NCS with the light exposure and the high temperature treatment. The degradations of dye, electrolyte, and TiO2electrode in the dye sensitized solar cells with the light exposure and thermal treatments are discussed in this paper.

We have successfully fabricated nickelsilicide-metalgate MOS capacitors at a low temperature of 280åC by treating poly Si stacked SiO2/Si substrates with a Cl plasma containing NiCl. We have confirmed atomically sharp NiSi/oxide interfaces after the present process where any interface segregation can not be observed by cross-sectional TEM measurements. The present process allows a control of Ni concentration in the gate metal film and the work function in the gate metal is adjustable in the range from 4.3 to 4.9 eV, which is suitable for the Si CMOS process.