Light trapping effect of patterned back surface reflectors in substrate-type single and tandem junction thin-film silicon solar cells

Light trapping is a key issue to boost the efficiency of thin-film Si solar cells including μc-Si:H. In this paper, effect of textured back reflectors on light trapping in μc-Si:H cells has been investigated with self-orderly patterned Al substrates obtained by anodic oxidation. With increase in the period of the patterned substrates from 0 to 1.1 μm, the short circuit current densities of 1-μm-thick μc-Si:H cells on the patterned substrates significantly increase from 18 to over 24 mA/cm², which is attributed to the improved light trapping in the infrared region. It has been clarified that this enhanced light-trapping effect in longer wavelengths is mainly attributed to the improved light scattering at the rear side by comparing μc-Si:H solar cells with polished and as-deposited front surfaces. The effectiveness of the patterned Al substrates has also been demonstrated in an a-Si:H/μc-Si:H tandem cell with a bottom cell thickness of 1 μm, showing a higher conversion efficiency than the reference cell.     

一种新的纹理合成算法

现有纹理合成算法并不能保证合成物体的完整性,也不能使其分布与样本纹理保持一致。提出了一 种分层纹理合成算法。首先,采用归一化图像分割算法提取样本纹理中的视觉显著性前景物体,继而采用图像修复 算法修复背景,然后统计前景物体在样本纹理中的分布共生矩阵,以此作为约束,在背景图像上确定前景物体的分 布位置。实验结果表明,不仅可以对前景物体独立进行各种变换,得到任意分布的合成纹理,而且可以保证前景物 体的完整性。     

Structural characteristics of sorghum kernel: Effects of temperature

In this study, the effect of cold water, hot water, and steam tempering on sorghum kernel physical and mechanical properties was studied. Single kernel characteristics (SKCS), abrasive hardness, structural changes, and texture of kernels were evaluated as an effect of temperature. At the same moisture level, cold water tempered sorghum had both higher SKCS hardness and abrasive hardness than hot water and steam tempered sorghum kernels. The increase in abrasive hardness, SKCS-hardness index was highly correlated with the moisture content of kernel. The abrasive hardness index, which represents the pericarp properties, did not show any correlation with moisture content but had correlation to the structural changes. The SEM images indicated the structural changes in pericarp after hot water and steam treatment. Steam tempering methods made the pericarp tougher than the cold water and hot water tempering methods and, meanwhile, softened the endosperm by adding moisture to the kernel.     

Spectroscopic ellipsometry characterization of SiNx antireflection films on textured multicrystalline and monocrystalline silicon solar cells

We present a spectroscopic ellipsometry study of silicon nitride based antireflection films deposited on chemically textured multi- and monocrystalline silicon wafers. The ellipsometric parameters were measured from the near infrared to the ultra violet spectral region. We report the effective thickness and complex index of refraction parameters of the antireflection films from all studied surfaces, regardless of their microscopic morphology. We report on a method to make ellipsometric measurements of the effective optical constants and thickness parameters of thin films deposited on alkaline etched (100)-oriented monocrystalline silicon. The effect of the texture on the complex index of refraction can be described within an effective medium approximation approach. The optical properties are consistent with those obtained from a series of reference films deposited on flat silicon surfaces.     

Reactive chemical vapor deposition of Ti3SiC2 with and without pressure pulses: Effect on the ternary carbide texture

Ti₃SiC₂ layers were grown by reactive chemical vapor deposition (RCVD) of a H₂/TiCl₄ gaseous mixture on previously deposited SiC layers. A comparison was made between classical RCVD in which the gases continuously flow at a constant low pressure during several minutes in the reactor and pressure-pulsed RCVD (P-RCVD) in which the reactor is (periodically) (re)filled with the H₂/TiCl₄ gas and (re)emptied every few seconds. Long duration single treatments resulted in similar thick multi-phased coatings growing by solid state diffusion with both RCVD and P-RCVD methods. Conversely, in relation with the steps of nucleation and growth by surface reaction, the repetition of short duration SiC deposition/RCVD sequences with or without pressure pulses gave rise to Ti₃SiC₂ coatings with different textures.     

Improvement of ductility in magnesium alloy sheet using laser scanning treatment

This paper suggests a novel method for improving the ductility of magnesium alloy sheets using a laser scanning treatment combined with a defocusing technique. The crystallographic orientation on both surface regions of the AZ31B magnesium alloy sheet processed using this method was changed from a strong basal texture to an almost random texture. The laser-scanned magnesium alloy sheet showed enhanced tensile elongation of up to 50% with a similar a tensile strength.     

Optimization of the structural, microstructural and optical properties of nanostructured Cr:ZnSe films deposited by magnetron co-sputtering for mid-infrared applications

In order to obtain optimally adherent films having the highest mid-infrared photoluminescence efficiency, nanostructured Cr²⁺:ZnSe films were deposited at room temperature on various substrates by magnetron radiofrequency co-sputtering of a SiO₂ target covered by a given number of ZnSe and Cr chips, at different Argon pressures and radiofrequency powers. The deposition parameter effect on the compositional, structural, microstructural and optical properties of the films has been investigated using X-ray reflectivity and diffraction, optical transmission spectroscopy, transmission electron microscopy, and photoluminescence studies. The corresponding films are composed by highly textured cubic and hexagonal ZnSe phases and exhibit strong tensile in-plane residual stresses. The evolution of the tensile residual stress and porosity values are consistent with the optical properties of the layers, and in particular the evolutions of both optical gap and refractive index. The room temperature mid-infrared (2-3 μm) photoluminescence measurements under direct excitation (1850 nm) revealed that chromium has been incorporated in the Cr²⁺ active state, and the corresponding fluorescence efficiency for an optimized thin film is only two times smaller than the one of a Cr²⁺:ZnSe reference bulk single crystal.     

Performance evaluation of a novel sampling-based texture synthesis technique using different sized patches

We propose a novel sampling-based texture synthesis algorithm called Multipatch, which improves on the results of previous sampling-based algorithms by using patches of different size, and by minimizing global pasting errors. A key feature of the proposed algorithm is that it always converges to a local minimum. Multipatch, the patchwork algorithm, and Wei and Levoy’s multi-resolution texture synthesis algorithm, which is based on a tree-structured vector quantization method, are statistically analyzed and subjectively evaluated. The results of simulations show that the patchwork algorithm yields a perceptually acceptable texture in a shorter expected running time than the other two algorithms; however, Multipatch is the most efficient in terms of obtaining a good quality texture image.     

Impact of the acidification process, hydrocolloids and protein fortifiers on the physical and sensory properties of frozen yogurt

In our study, two acidification procedures, three stabilizers (guar gum, xanthan and carboxymethylcellulose) and two protein-fortifying agents (skim milk powder and whey powder) were evaluated based on their impact on the quality characteristics of frozen yogurts. Indirect acidification (blending of plain acidified milk with ice cream mix) was found to favour texture while direct acidification (fermentation of ice cream mix with starter culture), although it improved viscosity of mixes, did not enhance the sensory acceptance of frozen yogurts. The addition of 0.2% xanthan gum and the partial substitution (at the ratio of 3 : 1) of skim milk powder by whey powder increased overall acceptance and creaminess.     

Toasting of corn flakes: Product characteristics as a function of processing conditions

Toasting of corn flake is an important processing step that dictates the attributes of the finished product with particular reference to consumer acceptability. The effect of important toasting variables such as moisture content, temperature and time of toasting of corn flakes on quality attributes has been investigated employing response surface methodology (RSM). A central composite experimental design consisting of five coded levels (−1.682, −1, 0, 1 and 1.682) of each independent variables has been employed. The response functions are thickness of flake, bulk density, puncture force, colour parameters and the sensory overall acceptability. Further, the changes in the microstructure of the flakes have been monitored. The energy expenditure during the toasting process was also determined, and 721–746 J g⁻¹ of energy was required to have properly toasted flakes. These response functions can be correlated (r  0.82, p  0.01) with the independent variables by second order polynomials consisting of linear, quadratic and interaction terms. The effect of temperature and time usually dominates over the moisture content for toasting of corn flakes. Optimum conditions for achieving best puffing and overall acceptability have been obtained.