One-step Fabrication of Nanoporous Black Silicon Surfaces for Solar Cells using Modified Etching Solution

Currently, a conventional two-step method has been used to generate black silicon （BS） surfaces on silicon substrates for solar cell manufacturing. However, the performances of the solar cell made with such surface generation method are poor, because of the high surface recombination caused by deep etching in the conventional surface generation method for BS. In this work, a modified wet chemical etching solution with additives was developed. A homogeneous BS layer with random porous structure was obtained from the modified solution in only one step at room temperature. The BS layer had low reflectivity and shallow etching depth. The additive in the etch solution performs the function of pH-modulation. After 16-min etching, the etching depth in the samples was approximately 200 nm, and the spectrum-weighted-reflectivity in the range from 300 nm to 1200 nm was below 5%. BS solar cells were fabricated in the production line. The decreased etching depth can improve the electrical performance of solar cells because of the decrease in surface recombination. An efficiency of 15.63% for the modified etching BS solar cells was achieved on a large area, p- type single crystalline silicon substrate with a 624.32-mV open circuit voltage and a 77.88% fill factor.

Realization of conformal doping on multicrystalline silicon solar cells and black silicon solar cells by plasma immersion ion implantation

Emitted multi-crystalline silicon and black silicon solar cells are conformal doped by ion implantation using the plasma immersion ion implantation （PⅢ） technique. The non-uniformity of emitter doping is lower than 5 %. The secondary ion mass spectrometer profile indicates that the PⅢ technique obtained 100-rim shallow emitter and the emitter depth could be impelled by furnace annealing to 220 nm and 330 nm at 850 ℃ with one and two hours, respectively. Furnace annealing at 850 ℃ could effectively electrically activate the dopants in the silicon. The efficiency of the black silicon solar cell is 14.84% higher than that of the mc-silicon solar cell due to more incident light being absorbed.

Optically induced abnormal terahertz absorption in black silicon

The absorption responses of blank silicon and black silicon（silicon with micro/nano-conical surface structures） wafers to an 808-nm continuous-wave（CW） laser are investigated at room temperature by terahertz time-domain spectroscopy. The transmission of the blank silicon shows an appreciable change, from ground state to the pump state, with amplitude varying up to 50%, while that of the black silicon（BS） with different cone sizes is observed to be more stable. Furthermore,the terahertz transmission through BS is observed to be strongly dependent on the size of the conical structure geometry.The conductivities of blank silicon and BS are extracted from the experimental data with and without pumping. The non-photo-excited conductivities increase with increasing frequency and agree well with the Lorentz model, whereas the photo-excited conductivities decrease with increasing frequency and fit well with the Drude–Smith model. Indeed, for BS, the conductivity, electron density and mobility are found to correlate closely with the size of the conical structure.This is attributed to the influence of space confinement on the carrier excitation, that is, the carriers excited at the BS conical structure surface have a stronger localization effect with a backscattering behavior in small-sized microstructures and a higher recombination rate due to increased electron interaction and collision with electrons, interfaces and grain boundaries.

Subtle Variations in Surface Properties of Black Silicon Surfaces Influence the Degree of Bactericidal Efficiency

One of the major challenges faced by the biomedical industry is the development of robust synthetic surfaces that can resist bacterial colonization. Much inspiration has been drawn recently from naturally occurring mechano-bactericidal surfaces such as the wings of cicada(Psaltoda claripennis) and dragonfly(Diplacodes bipunctata) species in fabricating their synthetic analogs. However,the bactericidal activity of nanostructured surfaces is observed in a particular range of parameters reflecting the geometry of nanostructures and surface wettability. Here,several of the nanometer-scale characteristics of black silicon(bSi) surfaces including the density and height of the nanopillars that have the potential to influence the bactericidal efficiency of these nanostructured surfaces have been investigated. The results provide important evidence that minor variations in the nanoarchitecture of substrata can substantially alter their performance as bactericidal surfaces.

Challenges in Processing Diamond Wire Cut and Black Silicon Wafers in Large-Scale Manufacturing of High Efficiency Solar Cells

Texturing of diamond wire cut wafers using a standard wafer etch process chemistry has always been a challenge in solar cell manufacturing industry. This is due to the change in surface morphology of diamond wire cut wafers and the abundant presence of amorphous silicon content, which are introduced from wafer manufacturing industry during sawing of multi-crystalline wafers using ultra-thin diamond wires. The industry standard texturing process for multi-crystalline wafers cannot deliver a homogeneous etched silicon surface, thereby requiring an additive compound, which acts like a surfactant in the acidic etch bath to enhance the texturing quality on diamond wire cut wafers. Black silicon wafers on the other hand require completely a different process chemistry and are normally textured using a metal catalyst assisted etching technique or by plasma reactive ion etching technique. In this paper, various challenges associated with cell processing steps using diamond wire cut and black silicon wafers along with cell electrical results using each of these wafer types are discussed.

High-dielectric loss black silicon decorated with multi-nanostructure for wide-band mid-infrared absorption

Because of the excellent light-trapping ability of black silicon,it has emerged as a versatile substrate for photothermic applications.In this paper,multi-nanostructured black silicon with wide-band mid-infrared absorption properties for application in pyroelectric detectors is reported.Black silicon is fabricated on a substrate surface masked by Ag nanoparticle arrays using single-step etching of C_(4)F_(8)and SF_(6)plasma.The low absorption of black silicon in the mid-infrared region is improved when a secondary nanostructure with Pt nanoparticles and SiO_(2)thin films is deposited on the surface of the prepared black silicon by microelectromechanical system(MEMS)processes.Electrons are scattered at particle boundary,resulting in dielectric loss to incident infrared(IR)region.Compared to single black silicon,the structure decorated with the multi-nanostructure can achieve higher infrared absorption,which is contributed to the high-dielectric loss properties of the Pt nanoparticles.Simulations and experiments show that the thickness of black silicon and number of layers of platinum particles contribute to mid-infrared absorption,with wavelength ranging from 2.5 to 20.0μm,and the absorption reaches~90%.The proposed absorber provides a promising solution for thermal detectors.

Formation mechanism of multi-functional black silicon based on optimized deep reactive ion etching technique with SF_6/C_4F_8

This paper reports a controllable multi-functional black silicon surface with nanocone-forest structures fabricated by an optimized deep reactive ion etching(DRIE)technique using SF6/C4F8 in cyclic etching-passivation process,which is maskless,effective and controllable.The process conditions are investigated by systematically comparative experiments and core parameters have been figured out,including etching process parameters,pre-treatment,patterned silicon etching and inclined surface etching.Based on the experimental data,the formation mechanism of nanocone shape is developed,which provides a novel view for in-depth understanding of abnormal phenomena observed in the experiments under different process situations.After the optimization of the process parameters,the black silicon surfaces exhibit superhydrophobicity with tunable reflectance.Additionally,the quantitative relationship between nanocones aspect ratio and surface reflectance and static contact angle is obtained,which demonstrates that black silicon surfaces with unique functional properties(i.e.,cross-combination of reflectance and wettability)can be achieved by controlling the morphology of nanostructures.

INFLUENCES OF MODIFIERS ON SURFACE PROPERTIES OF WHITE CARBON BLACK AND MECHANICAL PROPERTIES OF SILICONE RUBBER

Various of modifiers were used to modify the surface activity of white carbon black. The oil absorption, viscosity, hydrophobic rate and burning loss of white carbon black and the mechanical propertiess of silicone rubber were measured. The influences of the modifiers on the properties of white carbon black and the mechanical properties of silicone rubber were discussed.

Electrochemical behavior of insulin on pretreated carbon black electrode enhanced with silicon carbide nanostructure

We previously reported the direct electrochemical detection of insulin at bare carbon electrodes. Here a novel modified acetylene carbon black paste electrode(SiC/CB-CPE), based on the outstanding characteristics of silicon carbide nanostructure,was developed for the electrooxidation of insulin in alkaline solution and it was characterized by cyclic voltammetry(CV) and electrochemical impedance spectroscopy(EIS) in 5 mmol/L Fe(CN)63-/4- solution. It is found that silicon carbide nanostructure doped into the CB-CPE greatly facilitates the redox electrochemistry of Fe(CN)63-/4- probe and the electrochemical oxidation of insulin. The electrooxidation of insulin is a one-electron and one-proton reaction and an irreversible adsorption-controlled electrode process. The anodic oxidation current increases linearly with the concentration of insulin from 1×10-7mol/L to1.2×10-6mol/L in 0.1 mol/L Na2CO3-NaHCO3 buffer solution(pH 10.0) and the detection limit was 50 nmol/L. In addition, the SiC/CB-CPE shows good sensitivity, reproducibility, renewability and capacity of resisting disturbance.

Sunlight loss for femtosecond microstructured silicon with two impurity bands

Black silicon, produced by irradiating the surface of a silicon wafer with femtosecond laser pulses in the presence of a sulfur-bearing gas, is widely believed to be a potential material for efficient multi-intermediate-band silicon solar cells. Taking chalcogen as an example, we analyse the loss of sunlight for silicon with two impurity bands and we find that loss of the sunlight can be minimized to 0.332 when Te^0（0.307 eV） and Te＋（0.411 eV） are doped into microstructured silicon. Finally, problems needed to be resolved in analysing the relationship between conversion efficiency of the ideal four-band silicon solar cell and the position of the introduced two intermediated bands in silicon according to detailed balance theory are pointed out with great emphasis.

Modeling of the impurity-induced silicon nanocone growth by low energy helium plasma irradiation

The formation mechanism of nanocone structure on silicon(Si)surface irradiated by helium plasma has been investigated by experiments and simulations.Impurity(molybdenum)aggregated as shields on Si was found to be a key factor to form a high density of nanocone in our previous study.Here to concrete this theory,a simulation work has been developed with SURO code based on the impurity concentration measurement of the nanocones by using electron dispersive x-ray spectroscopy.The formation process of the nanocone from a flat surface was presented.The modeling structure under an inclining ion incident direction was in good agreement with the experimental result.Moreover,the redeposition effect was proposed as another important process of nanocone formation based on results from the comparison of the cone diameter and sputtering yield between cases with and without the redeposition effect.

Study on Synthesis of Nanometer SiC Precursors with Sol-Gel of SiO_2-Lignin in the Pulp Black Liquor

In the process of synthesis of nanometer SiC precursors with sol-gel of SiO2 and lignin , the products of all sizes required can be controlled by the concentration of reac-t ants , pH, temperature, reaction and ageing time , and so on . The best conditions in this research are : the concentration of Na2SiO3 and organic matters are 4. 50% and 26.4% respectively, pH = 3.3 , T = 65℃ , ageing time is 30min , dried at 150 ℃ , the size of SiC precursors is about 2.0μm .

圆珠笔笔芯脂的设计开发与性能评价

随着我国圆珠笔产能的不断提升,我国已逐渐成为世界公认的制笔大国。在国家有关部门及相关政策的大力扶持下,圆珠笔墨水和配件加工技术等阻碍我国圆珠笔行业自主化发展的技术壁垒逐步被打破,然而现阶段国内关于笔芯脂的研究仍处于起步阶段,中高端笔芯脂产品仍主要依赖于国外进口。为此,采用无机稠化剂和硅油基础油为原料,并辅以一定的改性剂增强其稳定性,研制出一款高性能笔芯脂产品,相较于国外某高端笔芯脂产品具有更好的高低温性、抗挥发性、黏温性和储存稳定性,通过装笔测试对其使用性能进行全面评价,研制的笔芯脂表现出良好的高低温稳定性、耐冲击性和书写随动性,能够全面满足圆珠笔的使用要求.

纳秒脉冲激光制备黑硅及其光学性能的研究

利用纳秒脉冲激光器在常温常压室内环境下扫描刻蚀单晶硅片,通过改变扫描方式和扫描的线间距制备了各种不同结构的黑硅样品,重点研究了扫描方式、扫描间隔、高温吹氧退火时间等对黑硅光致发光(PL)特性的影响,以及不同参量制备的硅表面微结构对光吸收率的影响。利用透射电子显微镜、扫描电子显微镜、光学显微镜、拉曼和荧光光谱仪、吸收光谱仪等对制备的黑硅样品形貌、光吸收和PL发光特性进行了检测与表征,获得了吸收率高于90%且具有良好发光性能的黑硅结构样品。研究发现,采用线性扫描方式制备的黑硅样品的PL光谱主要分布在红光波段,而采用正交扫描方式制备的黑硅样品的PL光谱中在近红外900 nm附近有稳定的发光峰;此外,在黑硅样品中还观察到630 nm附近的电子局域态发光,并通过建立对应的物理模型解释了其发光机理。

正交试验法优化铂催化液体硅橡胶导电发泡材料

液体硅橡胶(LSR)除了具有硅橡胶的优势,还具有良好的流动性,易于加工,绝缘性限制了其在电子领域的应用。目前已有许多导电固体硅橡胶的研究,但国内关于导电LSR的研究较少,且都有一些共性问题,比如导电填料过多、硬度太高、密度过大等。为了降低铂催化LSR的导电填料添加量,并降低其密度和硬度,采用乙炔炭黑(CB)作为导电填料并将材料进行发泡,制备LSR导电发泡材料。但是,铂催化LSR还有无法使用常规含氮有机发泡剂以避免铂中毒的问题,因此需要采用其他发泡方法。因而采用羟基硅油(Si-OH)和水作为化学及物理发泡剂,蒙脱土(MMT)作为补强剂,为了得到综合性能良好的硅橡胶导电发泡材料,利用正交试验法,并进行单因素方差分析,研究了Si-OH,CB,MMT和水对材料发泡和力学性能及电导率的影响。结果表明,正交试验法可快速得到CB/LSR导电发泡最优配比:当LSR质量分数为56.1%,Si-OH为28.1%,CB为7%,MMT的质量分数为5.3%,水的质量分数为3.5%时,制备的发泡材料电导率为3.36×10^(-6)S/m,液体硅橡胶比纯LSR提高了9个数量级,密度为0.67 g/cm^(3),相比纯LSR降低了43%,邵C硬度为36,比纯LSR降低了33%。

积雪变化对东北农田黑土盐基离子及有效硅铝含量的影响

[目的]为探究冬季积雪深度变化下东北农田黑土盐基离子及有效硅铝含量的季节性变化特征。[方法]采用人工控制积雪深度的方法,通过测定除雪处理组(SR)、减雪处理组(SL)、自然积雪对照组(C)、增雪处理组(SA)的东北农田黑土环境因子(温湿度、含水率、pH、总有机碳)、盐基离子、有效硅以及活性铝,分析土壤盐基离子及有效硅铝的含量变化过程,以及两者对土壤环境因子的响应关系。[结果]积雪深度的降低使季节性雪被覆盖下黑土受到积雪的保温作用减弱,0-30 cm土壤温度及湿度(未冻水含量)显著下降,使水盐运移过程中未冻水携带的HCO_(3)^(-)含量减少,土壤平均pH受HCO _(3)^(-)含量影响分别变化-0.06,-0.04,-0.02,0.01。土壤的碱性降低,低价阳离子对高价阳离子在土壤胶体吸附电位的置换能力增强,使得交换态一价阳离子(Na^(+)、K^(+))含量升高,同时使交换态及碳酸盐态二价阳离子(Ca ^(2+)、Mg^(2+))含量降低。碳酸盐态二价阳离子与交换态Na+分别对TOC含量构成正向和负向的影响,使土壤平均总有机碳(TOC)含量随积雪深度的降低分别增长0.87,1.09,1.32,1.48 g/kg。盐基离子与土壤pH、TOC的相互影响关系使在积雪深度降低的条件下土壤pH与TOC含量降低,进而对土壤有效硅铝含量构成间接影响。TOC含量的降低削弱了土壤对低活性腐殖酸铝(Al-HA)的固持作用,pH的降低促进低活性铝向高活性交换态铝(Ex-Al)与单聚体羟基铝(Hy-Al)的转化,土壤铝毒性提升,同时促进有效硅的溶解,造成土壤硅的流失。[结论]气候变暖引起的中高纬度地区季节性积雪覆盖面积减少将影响冬季东北地区农田黑土的物质能量分布状态,并由此改变生长季节农作物的生长发育环境,研究提示为冬季东北黑土区土壤矿质元素的季节性变化过程提供了一定的科学依据。

基体模量对用于柔性传感器的导电聚合物复合材料电阻黏弹性的影响

导电聚合物复合材料(CPC)被广泛用于柔性电阻式传感器的制备。然而由于聚合物基体的黏弹性,导致其电阻响应呈现松弛、滞后等黏弹性现象,这将会对制备的传感器精确表征造成不利影响,故在材料制备阶段减小电阻黏弹性对基于CPC的柔性电阻式传感器具有重要意义。选择了常用的零维炭黑(CB)及一维多壁碳纳米管(MWCNT)为导电填料,并通过在质量分数3%~7%间改变硅橡胶(SR)固化剂质量分数来调节基体模量,研究了基体模量及纳米填料维数对CPC电阻黏弹性的影响。研究结果显示,纳米填料质量分数为3%时,随着基体模量的增加,CB/SR的电阻松弛比从15%增加到34%,多壁碳纳米管/硅橡胶(MWCNT/SR)的电阻松弛比从40%增加到47%;动态循环加载下的应变灵敏度也随基体模量的增加而下降。相同固化剂质量分数即相同基体模量时,与MWCNT/SR相比,CB/SR的电阻松弛比、动态循环加载下的应变灵敏度下降程度和“肩峰”更小。因此,在制备过程中减小基体模量、使用零维导电纳米填料CB,均可减小CPC的电阻黏弹性。

填料改性低黏度耐高温硅橡胶胶粘剂的制备与性能研究

针对硅橡胶胶粘剂高温烧蚀环境的使用性能和工艺性需求,合成了低黏度的苯基硅橡胶基础胶,并表征基础胶分子量分布、苯基含量和黏度。所制备的基础胶苯基含量22.5%~23.8%,黏度6530~11500mPa·s,挥发分0.30%~0.37%,说明基础胶的黏度和挥发分均处于较低水平,具有良好的工艺性。然后采用苯基硅橡胶基础胶与白炭黑、铁红、短切碳纤维混炼,制备室温硫化硅橡胶胶粘剂。采用三因素三水平正交试验考察了无机填料对硅橡胶胶粘剂黏度、拉剪强度、耐温性能的影响。研究结果表明:(1)从黏度和拉剪强度的极差分析可以看出,对黏度影响最大的为白炭黑,其次为短切碳纤维。添加白炭黑,会使拉剪强度与黏度同时增加,因此在黏度许可的范围内,提高白炭黑用量,可以提高拉剪强度。(2)对残碳率进行极差分析,铁红对于残碳率的影响远大于白炭黑、短切碳纤维。铁红能够显著提高硅橡胶胶粘剂的热稳定性,当铁红添加量为10份时,加温过程中的鼓胀和排气被明显抑制。

改性自流平硅酮密封胶材在戈壁机场跑道灌缝中的应用

为有效提高混凝土道面接缝的寿命、弹性、耐候性,本试验在不同黏度复配聚硅氧烷基础上,制备一种自流平硅酮密封胶材料,并探究白炭黑添加量、甲基三丁酮肟基硅烷交联剂添加量对硅酮密封胶体系性能的影响,以及该密封胶材料在机场跑道砼灌缝修补的应用。结果表明,当白炭黑添加量为5%、交联剂添加量为6%时,自流平硅酮密封胶拥有良好的自流平性能和力学性能,此时自流平厚度为3.59 mm,自流平时间为116 s,拉伸强度为0.54 MPa,拉伸断裂伸长率为238%。所制备的自流平硅酮密封胶材料具有良好的性能,可用于戈壁机场跑道砼灌缝修补。