一种新型腐蚀剂——醋酸钠溶液对单晶硅太阳电池表面织构化的作用

对晶向为(100)的p型单晶硅片进行表面刻蚀,制作减反射绒面。选用了一种新型的腐蚀剂,即醋酸钠(CH3COONa)溶液,用来腐蚀单晶硅太阳电池。通过分别改变醋酸钠溶液的浓度、温度以及腐蚀时间对硅片表面进行腐蚀发现,经醋酸钠溶液腐蚀后在硅片表面形成腐蚀坑大小适中、分布均匀的绒面结构。在醋酸钠溶液的质量分数为20%、温度为95℃、时间为40min的条件下腐蚀单晶硅片,在波长为700～1000nm之间获得较低的平均表面反射率,且最佳平均反射率为12.14%。从实验结果和成本因素考虑,这种腐蚀剂的成本很低,不易污染环境且重复性好,有利于大规模工业化制绒。     

乙二胺在单晶硅太阳能电池表面制绒中的应用

利用乙二胺(Ethylenediamine anhydrous,EDA)/异丙醇(Isopropyl alcohol,IPA)体系对单晶硅(100)面进行了各向异性腐蚀,研究了不同温度、不同反应时间条件下单晶硅表面的绒面结构和表面反射率。利用EDA/IPA体系得到的金字塔结构尺寸为8μm左右,但均匀性较差。在1.5%EDA、5%IPA体系中添加5%Na2SiO3,80℃反应15min后获得了平均反射率为11%、表面金字塔结构均匀且尺寸较小的单晶硅绒面。实验结果表明,Na2SiO3的引入使金字塔的尺寸从8μm左右降低至3μm左右,并且均匀度也得到改善。     

不同醇类对单晶硅绒面特性的影响

在单晶硅太阳电池的绒面制作过程中分别采用一元醇(乙醇、异丙醇)和二元醇(乙二醇、丙二醇)作为添加剂,比较它们对单晶硅绒面特性的影响.实验表明,一元醇可以降低化学反应速率,而二元醇可以加快反应速率,缩短制绒时间.二元醇相比一元醇具有更高的沸点,在制绒过程中挥发更少,可以减少药品的损耗.降低成本,然而二元醇的消泡效果比一元醇差,制绒时需要采用更大的初始浓度.扫描电子显微镜(sEM)结果表明,一元醇趋向于使绒面金字塔更均匀,而二元醇则容易导致绒面金字塔不均匀.反射谱的测试结果表明,采用二元醇作为添加剂进行制绒,相比一元醇,可以获得更低的硅片表面反射率.     

单晶硅小金字塔绒面及其对太阳电池性能的影响

研究了TMAH(四甲基氢氧化铵)和NaOH腐蚀液在制作单晶硅片小绒面中的应用,制作出平均尺寸小于2μm的金字塔绒面;比较了不同硅片预处理(酸减薄、碱减薄、原片)对金字塔绒面尺寸、均匀性、覆盖率以及反射率的影响以及电池的I-V性能,分析了不同绒面结构对接触电阻的影响;指出单晶硅小金字塔绒面是使用激光制备高效晶体硅太阳电池的关键.     

电化学刻蚀参数对高阻厚壁宏孔硅阵列表面形貌的影响

采用光电化学刻蚀方法,在电阻率为4～5 kΩ·cm的n-型[100]单晶硅片上制备了厚壁有序宏孔硅阵列。通过对比有限元法模拟诱导坑周围的电场分布,研究了刻蚀参数(电解液、光照、电压)对阵列表面形貌的影响。在刻蚀成孔的过程中,诱导坑对孔的限制受电场分布和实验条件的共同影响,出现刻蚀偏离的现象。模拟结果显示,诱导坑上的电场强度沿着单晶硅的[100]和[110]晶向的分布。这种分布的结果是,随着光照强度的提高和刻蚀溶液表面自由能的降低刻蚀由原光刻图形的(110)面向(100)面偏离。提高刻蚀电压可抑制刻蚀偏离,有利于诱导坑快速刻蚀成孔,从而形成规整的厚壁宏孔硅阵列。     

利用金属辅助化学腐蚀法在硅表面获得纳米绒面结构以提升多晶硅太阳电池效率

在硅片表面制备绒面结构能够有效降低太阳光在硅片表面的反射损失,是提高太阳能电池转换效率的一条重要途径。通过真空热蒸发法在多晶硅片上沉积纳米银颗粒,利用金属辅助化学腐蚀(MACE)法,制备了不同腐蚀时间下的纳米绒面结构,其中,腐蚀时间为60s的纳米绒面的平均反射率低至4.66%(300~1100nm)。同时,对腐蚀时间为60s的纳米绒面用KOH溶液进行优化处理,将KOH处理前后的多晶硅片采用常规电池工艺进行电池制备研究。对比发现,经过KOH处理后的电池效率比未经KOH处理的电池效率提高了0.43%。     

多晶硅太阳电池表面激光织构工艺研究

采用激光刻蚀,辅以化学溶液腐蚀对多晶硅片进行了表面织构.利用扫描电镜(SEM)、Helios LAB-rc反射率测试仪和Semilab WT2000少子寿命仪对样品进行了表征.结果表明,多晶硅表面经激光织构后表现出很好的陷光效果,反射率降低为8.0％.激光织构使硅片的少子寿命缩短,通过沉积Al2O3钝化薄膜可改善多晶硅片的电学性能.     

磁场方向对碱腐蚀构建多晶硅绒面结构的影响

在零磁场和2T、4T磁场中用NaOH溶液腐蚀制备多晶硅绒面结构,样品板平面分别平行和垂直于磁场放置。用电子天平称重表征硅片的腐蚀程度、用奥林巴斯LEXT OLS4100共聚焦显微镜观察多晶硅片形貌、用Ocean Optics USB4000光谱仪测量多晶硅片的反射率、用WT-1200硅片测试仪测量样品的少子寿命,研究了磁场方向对碱腐蚀构建多晶硅绒面结构的影响。结果表明：随着磁感应强度的提高多晶硅片的腐蚀程度严重,绒面结构变得均匀和细腻,反射率降低;在磁感应强度相同的条件下碱液中沿着磁场方向运动的OH^-离子不受磁场力作用,而运动方向与磁场方向不完全一致的OH^-离子受磁场产生的Lorenz力作用。Lorenz力使板平面垂直于磁场方向的硅片样品腐蚀程度更加严重、绒面和断层状结构细腻程度更加显著、少子的寿命更长、反射率更低。磁感应强度为4T时反射率降低到14.5%,在用碱液腐蚀制备多晶硅绒面结构过程中施加强磁场,板平面垂直磁场方向放置硅片减反射效果更加显著。     

湿法腐蚀硅片并生长氧化锌纳米棒作为太阳能电池减反层研究

在硅基太阳能电池表面制备减反层可以有效降低硅表面的反射率, 提高吸收率, 从而提高硅基太阳能电池的光电转换效率。本研究利用四甲基氢氧化铵(Tetramethyl Ammonium Hydroxide TMAH)溶液对(100)单晶硅进行各向异性腐蚀, 在表面腐蚀出金字塔结构, 得到了最低为6%左右的反射率。然后采用水热法在该衬底生长氧化锌纳米棒, 得到了最低小于3%的反射率, 比单采用腐蚀或者ZnO纳米棒生长的硅表面的反射率更低。这种减反方法工艺简单、高效, 有望得到应用。     

纳米金属银、铜辅助化学刻蚀制绒金刚线切割多晶硅的研究

以金刚线切割多晶硅为原料,研究不同纳米金属催化剂(银、铜)辅助化学刻蚀对纳米结构引入及多晶硅片表面制绒效果的影响。研究结果表明:不同纳米金属物种诱导刻蚀对硅片表面形貌结构的影响巨大,相比于纳米银辅助刻蚀形成的硅纳米线阵列结构而言,纳米铜辅助刻蚀形成的倒金字塔结构在各方面的性能均比较突出,大面积微尺度的倒金字塔阵列结构可以更完美地融合表面低反射率和钝化不佳之间的矛盾,且硅片表面切割纹去除效果明显。当金属铜辅助化学刻蚀制绒15 min时,倒金字塔结构最规则、均匀,且在300~1 100 nm波段范围内,反射率由原片的41.8%降低至5.8%。同时倒金字塔形貌具有优越的减反效果和去除切割纹能力,使得制绒金刚线切割多晶硅片有望用来制备高效率的太阳能电池。     

Optimization of textured structure on crystalline silicon wafer for heterojunction solar cell

Increasing the light scattering in monocrystalline silicon solar cells by surface texturing is an emerging field of practice in modern silicon photovoltaic. In this article, the surface micro-textures were performed on the monocrystalline silicon surface in potassium hydroxide solution without adding isopropyl alcohol. The parameters of the etching process such as concentration, time duration and temperature were examined to study the effects on shape and geometry of the microstructure. In addition, ray-tracing simulations of the light trapping were performed on these textured structures. The textured surfaces resemble the structures of uniform pyramids, mostly small pyramids, and mostly big pyramids. The simulation technique was applied in order to evaluate the light trapping effect by textured surfaces based on above pyramidal shape models. Afterwards, theoretical and experimental values of reflection data were compared. Such a simulation model was perceived as an effective tool for optimizing the micro structural shape, thus improving the light trapping. In this study, for solar cell applications, the double-side heterojunction solar cell with mostly big pyramids shape yielded an active area conversion efficiency of 16.3% with an open circuit voltage of 0.645 V, a short circuit current of 34.8 mA cm⁻² and a fill factor of 0.73.     

Nanostructure formation and passivation of large-area black silicon for solar cell applications

Nanoscale textured silicon and its passivation are explored by simple low-cost metal-assisted chemical etching and thermal oxidation, and large-area black silicon was fabricated both on single-crystalline Si and multicrystalline Si for solar cell applications. When the Si surface was etched by HF/AgNO(3) solution for 4 or 5 min, nanopores formed in the Si surface, 50-100 nm in diameter and 200-300 nm deep. The nanoscale textured silicon surface turns into an effective medium with a gradually varying refractive index, which leads to the low reflectivity and black appearance of the samples. Mean reflectance was reduced to as low as 2% for crystalline Si and 4% for multicrystalline Si from 300 to 1000 nm, with no antireflective (AR) coating. A black-etched multicrystalline-Si of 156 mm × 156 mm was used to fabricate a primary solar cell with no surface passivation or AR coating. Its conversion efficiency (η) was 11.5%. The cell conversion efficiency was increased greatly by using surface passivation process, which proved very useful in suppressing excess carrier recombination on the nanostructured surface. Finally, a black m-Si cell with efficiency of 15.8% was achieved by using SiO(2) and SiN(X) bilayer passivation structure, indicating that passivation plays a key role in large-scale manufacture of black silicon solar cells.     

不同形貌α-Fe2O3的水热法制备及性能研究

以Fe(NO_3)_3·9H_2O为原料,聚乙烯吡咯烷酮作为表面活性剂,NaOH、Na_2CO_3、CH_3COONa为形貌改变剂,采用水热法制备出不同形貌的α-Fe_2O_3,并研究了不同因素对产物形貌的影响。利用SEM、EDS、XRD、FTIR等手段对其物相及微观形貌进行表征,并探讨其生长机理。通过光催化降解酸性大红模拟废水考察不同形貌α-Fe_2O_3的光催化性能,实验结果表明,类桑葚状α-Fe_2O_3对酸性大红模拟废水的降解效果最好,降解率高达99.01%,具有潜在的光催化应用前景。     

Influence of stain etching on low minority carrier lifetime areas of multicrystalline silicon for solar cells

In this work the use of HF/HNO₃ solutions for texturing silicon-based solar cell substrates by stain etching and the influence of texturing on minority carrier lifetimes are studied. Stain etching is currently used to decrease the reflectance and, subsequently improve the photogenerated current of the cells, but also produces nanostructures on the silicon surface. In the textured samples it has been observed that an improvement on the minority carrier lifetime with respect to the samples treated with a conventional saw damage etching process is produced on grain boundaries and defects, and the origin of this effect has been discussed.     

Optical reflectance and transmission of a textured surface

The reflectivity of a solar thermal or solar electric device is a key parameter in efficiency. In the recent solar device literature, highly “textured” surfaces have been shown to reduce the reflectivity appreciably. The theoretical model used to describe this phenomenon is light trapping by multiple reflections. Surface roughness has also been considered by others through statistical scattering theory. The range of validity of either model is limited to a scale of texture larger than the wavelength of the light. For the micron scaled texture which is of interest, however, both approaches fall into the category of approximate solutions to approximate models of the surface.We approached the problem differently. We obtained the effects of texture on reflectivity and transmission through an exact calculation of a boundary layer whose complex dielectric constant is an appropriate average of the bulk dielectric constant of the material and air. The calculations were made for arbitrary angles of incidence, polarization and wavelength, as well as for arbitrary spatial variation of the dielectric constant through the boundary layer. We developed the spatial variation through effective medium models for a discontinuous surface layer. Finally, we compared the computer calculation with an exact analytic treatment for normal incidence, as well as with experimental reflectivities on several textured surfaces.     

The modulation of surface texture for single-crystalline Si solar cells using calibrated silver nanoparticles as a catalyst

We have employed Ag nanoparticles with calibrated size as catalysts to modulate the surface texture of single-crystalline Si surfaces for reducing sunlight reflectivity. Both experiments and theoretical analysis have proved that a well-organized microporous structure on the pyramids can be obtained by optimizing the size of Ag nanoparticles and the texturing time, and the Si wafer with such structures can effectively reduce the reflectivity of sunlight. However, based on the conventional cell fabrication process, the performance of silicon solar cells with such microporous structures gets degraded. It is closely associated with the strong surface recombination and the high phosphorus diffusion barrier induced by the microporous textures. These results are interesting for us to understand the application of nanotechnology on the silicon solar cell.     

Effect of laser surface texturing on Si3N4/TiC ceramic sliding against steel under dry friction

In efforts to investigate the influence of the surface texturing on the Si₃N₄/TiC ceramic, laser surface texturing (LST) was performed on the Si₃N₄/TiC ceramic by an Nd:YAG laser and different geometrical characteristics of regular-arranged micro-grooved textures were fabricated on the surfaces. The tribological properties of the textured and smooth samples were investigated by carrying out sliding wear tests against steel balls under dry condition using a ball-on-disk tribometer. Effect of surface texturing on the stress distribution was studied by finite element method (FEM). Results show that the textured surfaces exhibited lower friction coefficient and excellent anti-wear properties compared with smooth surfaces. The tribological characteristics depended greatly on the size and density of the micro-grooves, and the geometrical characteristics of the surface textures have a significant effect on the tribological behavior. Among the patterns investigated, the wavy-grooved samples exhibit the lowest friction coefficient and wear rate; and a large texture density may be the best for reduction of friction and wear of textured samples. While, the wear rate of balls sliding against textured surfaces is larger than that of balls sliding against smooth surfaces. FEM results show that surface texturing can improve the stress distribution of contact interfaces and reduce stress concentration.     

以石英为原料制备白炭黑的实验研究

为研究白炭黑的制备工艺,以石英原矿、浓硫酸、Na2CO3和NaOH为原料,利用煅烧-淬冷-硫酸酸洗工艺制备质量分数大于99%的高纯石英粉,并利用煅烧-沉淀法制备非晶白炭黑。采用X射线荧光(XRF)和X射线衍射(XRD)等手段研究钠源(Na2CO3)与石英比例、不同钠源(NaOH)等对白炭黑品质的影响。结果表明:将石英与Na2CO3或NaOH混合煅烧后制成溶液,通入CO2气体后可生成非晶白炭黑,最佳工艺条件为:n(Na2CO3)∶n(SiO2)=1∶1,混合物在1 250℃下煅烧2.5 h。     

微量Si在W－7Ni－3Fe重合金中的行为

研究了掺到原料Ｗ粉中微量Ｓｉ（４００ｐｐｍ）在Ｗ－７Ｎｉ－３Ｆｅ重合金中的分布及在液相烧结过程中的行为．结果表明，Ｓｉ主要以固溶形式分布在Ｗ晶粒中．Ｘ射线光电子能谱（ＸＰＳ）分析发现，在掺杂Ｓｉ的Ｗ－Ｗ及Ｗ－基体相界面富集ＳｉＯ２和Ｎａ２ＳｉＯ３在未掺杂试样的断口表面发现了较弱的ＷＯ２的ＸＰＳ谱，而在掺杂合金中未发现ＷＯ２．