多晶硅表面陷阱坑形貌对表面光反射率的影响

利用光学傅里叶变换研究多晶硅绒面微结构形貌与反射率之间的关系。理论分析表明:多晶硅绒面反射率与表面微结构形貌、单位面积上陷阱坑数量有关。如绒面由V字型槽或坑构成,则绒面反射率比较高;如多晶硅表面上密集布满U字形坑或槽、内表面绒面化,这种结构构成的绒面反射率低。实验上用不同比例的酸液刻蚀多晶体表面,用扫描电镜(SEM)观察多晶硅表面SEM图,测量了其表面反射率,分析表面结构形貌与反射率的关系。实验结果与理论分析相吻合。     

Large-scale black multi-crystalline silicon solar cell with conversion efficiency over 18 %

In this paper, large area multi-crystalline silicon (mc-Si) solar cells of 156 mm × 156 mm were fabricated by the combination of Ag-assisted etching and sodium hydroxide (NaOH) treatment. Scanning electron microscope, UV–Vis–NIR spectrophotometer, external quantum efficiency measurement system, and current–voltage test were used to characterize the etched black silicon wafers and the fabricated solar cells. It was found that, though the black mc-Si without NaOH treatment showed a lowest reflectance of 2.03 % in the wavelength of 400–900 nm, the maximum conversion efficiency came from the mc-Si solar cells produced by combination of Ag-assisted etching and NaOH treatment. Though the solar cell with additional NaOH treatment for 30 s presented a reflectance of 5.45 %, it presented the highest conversion efficiency of 18.03 %, which is 0.64 % higher than the traditional mc-Si solar cell (17.39 %) and much higher than that of the black mc-Si solar cell without NaOH treatment (16.24 %).     

表面钝化对多晶硅绒面形貌的影响

多晶硅表面制绒技术是太阳能光伏产业亟待突破的一个关键技术.本文根据多晶硅强酸制绒的基本原理,提出了表面活性剂钝化多晶硅表面以降低硅原子与酸反应速度从而改善多晶硅绒面形貌的方法.实验研究了不同含量的添加剂对酸液刻蚀多晶硅绒面形貌的影响,用扫描电镜观察对应的绒面结构,用积分反射仪测量其绒面的表面反射率.实验结果表明:加入活性剂后酸液能使多晶硅表面陷阱坑分布更加均匀,并且能有效消除产生漏电流的缺陷性深沟槽,样品表面反射率比较低,其表面反射率降低到21.5%.与传统酸液腐蚀的多晶硅绒面结构相比,陷阱坑密度明显增加,这种方法在多晶硅太阳电池的生产中是有价值的.     

超声驻波场粒子二维运动控制机理与模型研究*

为了将正交超声驻波技术用于多晶硅陷光结构网格化微加工,以达到均匀加工的目的,本文从理论、模拟和实验等方面研究了粒子由无规则排列到超声作用后形成二维网格状排列的运动过程,网格化控制机理,并建立了二维运动方程。计算机仿真结果与实验结果一致,表明应用超声驻波进行网格化微纳加工设想是可行的。     

Mass production technology for multicrystalline Si solar cells

The worldwide shipments of the PV modules in the last 10 years show an increase of about 20% per year. The worldwide PV modules shipments were 201 MW in 1999. About 85% modules have made from crystalline silicon. The multicrystalline silicon (mc-Si) modules shipments have showed substantial increase. PV market would be expected to increase by the development of low cost and high technologies of mc-Si solar cells. This paper reviews recent progress in mass production technologies of mc-Si solar cells.     

Hydrogen passivation of multi—crystalline silicon solar cells

The effects of hydrogen passivation on multi-crystalline silicon (mc-Si) solar cells are reported in this paper. Hydrogen plasma was generated by means of ac glow discharge in a hydrogen atmosphere. Hydrogen passivation was carried out with three different groups of mc-Si solar cells after finishing contacts. The experimental results demonstrated that the photovoltaic performances of the solar cell samples have been improved after hydrogen plasma treatment, with a relative increase in conversion efficiency up to 10.6\%. A calculation modelling has been performed to interpret the experimental results using the model for analysis of microelectronic and photonic structures developed at Pennsylvania State University.     

薄膜层状外延生长的光学原位实时监测方法

综述了几种用于监控薄膜外延生长的光学原位实时监测方法的进展。其中光反射差法／光反射各向异性谱（ＲＤＳ／ＲＡＳ）和ｐ偏振反射谱（ＰＲＳ），表面光吸收（ＳＰＡ），椭偏仪（ＳＥ）等。在外延过程中已观测到了薄膜层状外延周期振荡。     

Spectral selectivity of nickel and chromium rough surfaces

The reflectance of metal surfaces with sinusoidal roughness of different periods and depths has been investigated experimentally. The results show clearly that the surface structure can be used to modify the optical properties of metal surfaces at different wavelengths. With a proper choice of groove depth to period ratio, nickel or chromium coatings on gratings have low reflectance in the short wavelength region, but achieve high reflectance in the infrared region. A solar absorptance as high as 93% has been obtained from such a surface. The surfaces are thought to be representative for randomly rough surfaces provided proper correlation length and height variation are chosen. Further, as the absorber is made of a single metal surface, it could be highly temperature resistant.     

基于多角度偏振载荷数据的中国典型地物偏振特性研究

相对于传统的光学遥感, 多角度偏振遥感不仅可以获取辐射强度信息, 而且可以获取偏振强度信息. 基于多角度偏振卫星载荷观测的中国典型地物的偏振反射率数据, 获取了地表偏振双向反射模型——Nadal模型的中国区域模型参数值. 在此基础上, 基于修正的Nadal模型研究了中国区域森林、草地、沙漠三种典型地物的多角度偏振特性. 研究表明: 1)各地物的偏振反射率均随着散射角的增大而减小, 随着太阳天顶角和卫星观测天顶角的增大而增大; 2)森林、草地和沙漠三种典型地表偏振反射率存在明显差别, 森林的偏振反射率最低, 草地的偏振反射率次之, 沙漠的偏振反射率大约为森林的两倍; 3)不同地物之间的偏振反射率差值均随着卫星观测天顶角和太阳天顶角的增大而增大. 研究结果可为基于多角度偏振遥感数据探测地表偏振特性和反演气溶胶参数提供先验知识.     

气溶胶垂直非均一分布对天空背景亮度的影响

对白天天空背景亮度进行了数值实验;模拟了不同标高下的气溶胶垂直分布对天空背景亮度的影响;比较了不同垂直分层和整层均匀气溶胶分布下,天空背景亮度的相对偏差,并分析了天空背景亮度对地表反射率的敏感性。结果表明:给定气溶胶光学厚度下,不同标高的垂直分布得到的天空背景亮度差别很大;天空背景亮度对地表反射率和气溶胶总光学厚度都比较敏感,敏感程度受太阳-观测几何的影响。     

Consistency of the Surface Roughness Determined from Soft-X-Ray Reflectance and Surface Profiles Measured Using a Scanning Tunnelling Microscope: Coherence Length of the Soft X-Rays

There exists serious inconsistency between the rms surface roughness determined from the Debye-Waller factor for the soft-x-ray reflectance analysis and that measured with an optical surface profiler. We have measured the surface profile of evaporated films using a scanning tunnelling microscope, and reproduce the profile with the Fourier components whose spatial wavelength is shorter than the coherence length of the incident soft x-rays in the reflectance measurement. The rms surface roughness derived from the high-pass filtered profile agrees well with that determined using the reflectance measurement. This result explains straightforwardly the photon-energy dependence of the surface roughness estimated by the soft-x-ray reflectance method.     

Scanning infrared microscopy investigation of copper precipitation in cast multicrystalline silicon

The behavior of copper precipitation in cast multicrystalline silicon (mc-Si) annealed at different temperatures under air cooling (30 K/s) or slow cooling (0.3 K/s) was investigated by scanning infrared microscopy (SIRM). Comparing to Czochralski-grown silicon (Cz-Si), copper precipitated more easily in mc-Si, and the lowest temperature of copper precipitation in mc-Si was about 700 °C, lower than that in Cz-Si. It was also observed that copper preferably precipitated on grain boundaries so that near the grain boundaries the denuded zone formed. The results indicate that the defects including dislocations, grain boundaries and microdefects, as the heteronucleation sites, enhanced copper precipitation. Moreover, cooling rates had a great influence on the copper precipitation, especially at lower annealing temperatures. Generally air cooling led to the formation of high density of copper-precipitate colonies.     

Nucleation and growth studies of gold films prepared by evaporation and ion-assisted deposition

Thin gold films have been deposited onto glass substrates by electron-beam evaporation and by oxygen and argon ion-assisted deposition. The nucleation and growth of the films have been monitored in situ by ellipsometry and spectral reflectance and transmittance measurements. The composition of the film surface has been characterized by ion-scattering spectroscopy. These techniques show that the thickness at which coalescence of gold islands occurs is less for both ion-assisted films than for the evaporated film deposited on a clean substrate. Monitoring of coalesced films during sputter-etching combined with measurements of reflectance from both sides of the coated surface indicate that all films have a layer of density less than bulk near the air-film interface, and for evaporated and argon ion-assisted films, another near the gold-substrate interface. Oxygen ion-assisted films showed no evidence of an interfacial layer near the substrate and it is concluded that these films had a much greater area of contact with the substrate than evaporated or argon ion-assisted films.     

Effect of surface roughness on surface plasmon resonance absorption

The absorption of light by surface plasmons has been studied using the method of attenuated total reflection. The reflectance from a quartz-Ag interface has been measured as a function of angle and surface structure for the wavelength region from 3600 to 6000 . It is shown that the reflectance minimum for a smooth Ag film is changed in both angular position and spectral half-width by roughening the Ag surface with CaF₂ underlayers. Dispersion curves are presented which show that the wave vector of a surface plasmon propagating on an irregular surface is greater than that of an equally energetic surface plasmon propagating on a planar surface.     

Photocatalytic mineralization study of malachite green on the surface of Mn-doped BiOCl activated by visible light under ambient condition

Manganese doped BiOCl has been synthesized by hydrolysis method and characterized by X-ray diffraction (XRD), scanning electron micrographs (SEM) and diffusive reflectance spectra (DRS) methods. Interesting results have been obtained from diffusive reflectance spectra. XRD results show a decrease in the lattice parameter for Mn-doped BiOCl and UV-vis measurement reveals that there is a shift in the optical absorption edge toward higher wavelength, which indicates a decrease in the band gap upon Mn doping. The increased photocatalytic activity in degradation of malachite green dye by Mn-doped BiOCl might be due to increase in life time of photogenerated electrons and holes due to scavenging of electrons by Mn, charging the particle surface due to electron on the surface, which enhances the adsorption of dye molecules, or/and decreased crystallite size. The effect of key operating parameters have also been investigated. Complete mineralization has been confirmed by COD analysis. An assumptive reaction mechanism has also been proposed.     

A PCA study to determine how features in meteorite reflectance spectra vary with the samples’ physical properties

Meteorites have advanced our knowledge of processes in the Solar System with the application of high precision instruments here on Earth. The study of asteroids, the source of most meteorites, has in turn given us knowledge regarding the large scale evolution of the Solar System. Using the complementary information that asteroids and meteorites give us the story of our cosmic backyard can be more easily read. One efficient way to link meteorites to asteroids is by matching their respective reflectance spectra. There have been few convincing matches because of observational and scale differences as well as an incomplete knowledge of the light scattering physics involved. To better interpret the reflectance data we need to know the dependencies of the reflectance on physical properties and develop techniques for better comparisons of data sets. For these purposes we utilise our own measurements of 26 different meteorites together with spectra available on the NASA PDS.We find that normalisation of reflectance at a wavelength between 1.1 and 1.3 μm gives the closest match of spectra from meteorites common to both data sets. The depth of the spectra bands deepens by similar amounts for different types of surface texture alterations i.e. rock to sawn surface, rock to polished surface and rock to powdered surface. Principal Component Analysis (PCA) is able to easily place carbonaceous chondrites, ordinary chondrites and achondrites into distinct groups using their reflectance spectra. We track the variation of spectral features in principal component space by using a set of meteorite spectra synthesised from mineral and elemental spectra. A spectral agent that reduces the reflectance at all wavelengths is required, in addition to olivine, pyroxene and carbon, to generate a set of synthesised spectra to match the distribution of measured spectra, in principal component space.     

利用地表土壤的反射光谱勘探油气的方法研究

反射光谱分析提供了一种高效和低成本的鉴别物质成分和结构的方法,油气微渗漏理论则建立了油气藏与其上部地表特定蚀变之间的因果关系,因此,可以通过检测地表蚀变的反射光谱来勘探油气。野外实地测量和高光谱遥感均能够实现反射光谱的检测。文章首先提出了典型含气区测点的光谱曲线的宏观特征;然后,给出了一种基于野外测量的反射光谱来确定特定蚀变的地表分布(即分类)的方法。将本方法应用于青海××地区野外测量的反射光谱的分析中,得到的蚀变异常区与该地区的已有气田成功吻合。本方法的鲁棒性实验表明,当分类过程中选用不同的参数组合(例如：分类样本,研究波段范围和相似度阈值)时,均能得到较好的分类结果。为该地区进行中的Hyperion高光谱遥感油气勘探项目提供了有效的分类样本和参考算法。     

黑硅材料的制备及其光学特性

采用金催化化学腐蚀和钝化两个过程成功制备了黑硅。利用原子力显微镜、分光光度计、红外光谱仪和光致发光光谱仪分别对黑硅的微观结构、反射率、表面状态和发光性能进行了研究。结果表明:黑硅表面呈现山峰状的微观结构,其平均反射率可低至3.31%。光致发光光谱上出现了3个发光峰,分别由量子限制效应、硅氧烯、杂质和缺陷引起。