纳秒级宽带KrF激光时间脉冲整形

对纳秒级宽带KrF激光脉冲的时间整形进行了研究。采用受激布里渊散射(SBS)脉冲压缩KrF激光获得短脉冲,通过脉冲堆积获得KrF激光时间整形脉冲。利用激光放大器对整形脉冲进行放大,对KrF激光整形脉冲的形状影响较大。通过对放大前整形脉冲形状的调整,在放大后可以得到所需形状的整形脉冲,一次放大能量输出可达50 mJ,二次放大能量输出可达300 mJ。理论分析与实验结果一致。研究表明,短脉冲堆积和放大器放大的组合方案具有较强的整形能力。     

多晶硅片少子寿命的影响因素研究与分析

为了提高多晶硅片的转换效率,提高多晶硅片少子寿命是一个重要的方法和途径,然而在生产过程中影响多晶硅片少子寿命的因素有很多,主要有杂质含量,硅片厚度及晶粒尺寸均匀性等。通过对分凝原理的研究,利用微波光电导测试原理对多晶硅锭少子寿命的分布做了分析,并对硅片厚度及晶粒尺寸进行研究,经过研究发现,多晶硅片少子寿命主要受原料金属杂质含量的大小,硅片厚度及晶粒尺寸均匀性等因素的影响。     

脉冲数目和重复频率对纳秒激光推进的影响

以抛物形点聚焦激光推进器模型为研究对象,数值模拟了脉冲重复频率在2~50Hz范围内吸气式多脉冲纳秒激光推进的流场演变过程,分析了脉冲数目和重复频率对推进性能的影响。结果表明:随着脉冲数目的增加,喷管内气体密度减小、温度升高,导致平均冲量耦合系数下降,但纳秒脉冲激光作用获得的平均冲量耦合系数明显高于微秒脉冲激光;相同脉冲数目条件下,随着脉冲重复频率的增大,流场恢复时间缩短,使得流场状态不能及时恢复,导致平均冲量耦合系数下降,其中脉冲重复频率f10 Hz时的下降趋势明显大于f10 Hz。     

离焦量对空气中纳秒激光打孔效率的影响

用波长1.06μm,脉冲半峰全宽(FWHM)约10 ns的Nd∶YAG激光照射在薄铜靶上,研究了打孔效率同离焦量之间的关系。实验中脉冲能量分别为26 mJ,52 mJ,85 mJ,204 mJ和274 mJ,在各脉冲能量下,改变离焦量,测出相应的打孔效率。结果表明,离焦量是影响打孔效率的重要因素;实际打孔过程中,采用较低的激光功率密度和 3~ 4 mm的离焦量是合理的选择。当离焦量d<0时,打孔效率主要由激光照射产生的热烧蚀、等离子体屏蔽两个物理机制决定;当离焦量d>0时,打孔效率是激光照射产生的热烧蚀、等离子体屏蔽和焦斑处空气等离子体辐射的促吸收效应共同作用的结果。     

激光脉冲宽度对红外光学材料稳定性的影响

连续波激光和脉冲激光对光学材料不同的破坏机理决定了解决其光学稳定性的不同途径。为了确定红外光学材料破坏机理变更的边界，作者将所有激光作用都看为脉冲的，确定了激光破坏阈值，并记录其特点。为了研究KCl单晶的破坏特点，建立了图1所示装置。它可用宽孔径激光照射样品，并可在偏振光中对晶体的双折射图进行高速摄影［门r图1实验装置光学系统图对一知几器；2一激光辐射光学物理参数测量系统；3一高速照相扯；4一起价器；5一电火花放电器；6一没反射屏图2微不均匀性吸收产生激光（。）和内应力逐渐积累（6～．·）时光学元件破坏的照…     

紫外激光切割Si片的实验研究

报道了用193nm准分子激光切割硅片的实验结果。采用柱透镜光学系统及“热劈裂法”获得小于15μm的切缝及小于5μm的切面不平整度。     

激光脉冲波形对推力器性能的影响

激光推力器性能优化是激光推力器研究的重要组成部分。受硬件条件的限制,激光推进领域激光脉冲时间波形对推力器性能影响的研究并未广泛展开。以两台CO2激光器的实际脉冲波形为基准,建立了两组激光能量输入模型,其波形时间分布相似,单脉冲能量相同,但脉冲持续时间及峰值功率不同。数值计算比较了不同脉冲波形下抛物型激光推力器的性能,结果表明:峰值功率和脉冲持续时间是影响推力器性能的重要参数,高功率短持续时间的脉冲波形更有利于提高冲量耦合系数和推力;两种实际脉冲波形的冲量耦合系数数值计算结果分别为40.9×10-5N.s/J,30.0×10-5N.s/J,与文献报道实验测量结果基本吻合。为激光推进CO2激光器的脉冲波形设计提供支持及研究思路,具有一定参考价值。     

皮秒和纳秒YAG脉冲激光离体血管成形术的实验研究

采用皮秒和纳秒YAG激光脉冲分别对试管内血栓、猪主动脉血栓及猪动脉血管壁进行了详细的激光气化实验研究。给出样品气化深度与激光脉宽、波长、单次脉冲能量和辐射总能量的关系曲线,并对样品作了组织学检查。     

陶瓷涂层对中红外探测器抗激光性能的影响

中红外激光器功率的不断提高使得传统红外成像制导武器临着前所未有的激光威胁.较高能量的激光会使导引头光机系统内部产生杂散光,从而干扰导引头正常工作.为增强当前红外成像导引头内部核心器件探测器的抗激光干扰和损伤能力,本文采用新型高吸收型陶瓷涂层材料增加导引头光机系统对杂散光的吸收能力,针对高吸收型陶瓷涂层和磨砂玻璃两种漫反射材料,通过等效实验对比了不同入射激光功率对红外探测器的干扰效果.研究结果表明:采用普通漫反射材料时,探测器在功率密度101.3 mW/cm2处达到饱和;而采用高吸收型陶瓷涂层材料后,入射激光在探测器像面上的饱和功率密度阈值增大到784.5 mW/cm2,其抗激光干扰能力相比于普通漫反射材料提高了近8倍.本文研究结果证明了采用高吸收型陶瓷涂层材料有助于增加红外成像导引头内部光机结构的消杂散光能力,能够有效提升现役导引头抗激光干扰能力,延长红外制导武器的战场生存周期.     

纳秒激光抛光表面的波纹形成机理

为探究激光抛光中引入的波纹的形成原因,通过纳秒光纤激光对718合金和304不锈钢进行了激光抛光,考察激光抛光导致的波纹效应.结果 表明:激光抛光产生的波纹(尺度为数十微米)与激光脉冲作用间距(10 μm)差别较大;不同激光能量产生的波纹在幅度上有差别,波纹的振幅随激光能量的减小而减小;波纹波长随激光能量的变化不大,具有...     

Structural inhomogeneities in polycrystalline silicon on glass solar cells and their effects on device characteristics

The effects of electrostatic fluctuations due to charged extended defects and strain‐induced bandgap fluctuations are examined in polycrystalline silicon on glass solar cells. The analysis is based on models previously applied to Cu(In,Ga)Se₂ solar cells, but with a new interpretation of the local ideality factor associated with electrostatic fluctuations. It is shown that electrostatic fluctuations become influential to the cell voltage properties as the absorber dopant concentration falls below a certain threshold (a few 10¹⁵ cm⁻³), and the degradations to the open circuit voltage and fill factor are expected to increase with further lowering of dopant density. It is equally plausible that the electrostatic fluctuations originate from charged dislocations or grain boundaries. Bandgap fluctuations on the other hand can be detrimental to the open circuit voltage of cells of any absorber dopant density. However, this voltage degrading effect is seen only in the cells deposited by electron‐beam evaporation, and not amongst those made by plasma enhanced chemical vapour deposition. Copyright © 2011 John Wiley & Sons, Ltd.     

超短脉冲激光对单晶硅太阳能电池的损伤效应

太阳能是未来的主要能源之一,关于太阳能电池的研究也逐渐成为热点。长期以来,人们对太阳能电池的高能粒子辐射特性进行了广泛的研究,对其激光辐照损伤特性的研究却很少。随着光电对抗技术的发展,对这方面的研究需求也越来越迫切。研究了532 nm、20 ns和300 ps脉冲激光对单晶硅太阳能电池的辐照效应,分析了超短脉冲激光对单晶硅太阳能电池的损伤机理。对比了超短脉冲激光和长脉冲激光、连续激光的损伤机理的异同。阐述了在激光单脉冲能量一定的情况下,损伤效果与脉宽和重频的关系。通过分析,指出了太阳能电池损伤的主因,激光对太阳能电池的破坏主要是依靠热效应。     

Material requirements for the adoption of unconventional silicon crystal and wafer growth techniques for high‐efficiency solar cells

Silicon wafers comprise approximately 40% of crystalline silicon module cost and represent an area of great technological innovation potential. Paradoxically, unconventional wafer‐growth techniques have thus far failed to displace multicrystalline and Czochralski silicon, despite four decades of innovation. One of the shortcomings of most unconventional materials has been a persistent carrier lifetime deficit in comparison to established wafer technologies, which limits the device efficiency potential. In this perspective article, we review a defect‐management framework that has proven successful in enabling millisecond lifetimes in kerfless and cast materials. Control of dislocations and slowly diffusing metal point defects during growth, coupled to effective control of fast‐diffusing species during cell processing, is critical to enable high cell efficiencies. To accelerate the pace of novel wafer development, we discuss approaches to rapidly evaluate the device efficiency potential of unconventional wafers from injection‐dependent lifetime measurements. Copyright © 2015 John Wiley & Sons, Ltd.     

Characterization of polycrystalline silicon wafers for solar cells sliced with novel fixed‐abrasive wire

For slicing crystalline silicon ingots, we have developed a novel fixed‐abrasive wire where diamond grit is fixed onto a bare wire by resin bonding. The properties of the wafers sliced using a multi‐wire saw with the fixed‐abrasive wire have been investigated. When compared with the wafers sliced with the loose‐abrasive wire, the slicing speed is improved by approximately 2.5‐fold and the thicknesses of saw‐damage layers are reduced by more than a factor of two. Polycrystalline silicon solar cells have been fabricated for the first time utilizing the wafers sliced with the fixed‐abrasive wire, and the cells with the saw‐damage etching depth of 7 µm have shown photovoltaic properties comparable to those prepared using the wafers sliced with the loose‐abrasive wire and subsequently etched to remove the damage layers up to 15 µm. It has been clarified that wafer slicing using the fixed‐abrasive wire is promising as a next‐generation slicing technique for fabrication of solar cells, particularly thin silicon cells where the wafer thicknesses approach or become less than 150 µm. Copyright © 2010 John Wiley & Sons, Ltd.     

多晶硅太阳电池的氮化硅钝化

全面介绍了等离子增强化学汽相沉积 ( PECVD)纳米氮化硅 ( Si Nx∶ H)光电薄膜的技术发展及现状 ,分析了 PECVD法沉积的 Si Nx∶ H薄膜对多晶硅太阳电池的体钝化和表面钝化机理     

Characterization of laser carved micro channel polycrystalline silicon solar cell

In this study the efficiency of polycrystalline silicon solar cells was increased carving micro channel structures using a laser. In research to date, micro channel structures on the surface of polycrystalline silicon solar cells have been manufactured and studied. In an experiment polycrystalline silicon solar cell with micro channel structures on the surface demonstrated an increase in efficiency of 0.23-1.50%, as the radius of the micro channel structures varied from 15 μm to 35 μm. Micro channels also improved the Fill Factor of polycrystalline silicon solar cells. However, the efficiency started to decrease when the radius of the micro channel structures was greater than 40 μm. Detailed features of the variation in current voltage of polycrystalline silicon solar cells with micro channels are discussed.     

Investigation of laser ablation on boron emitters for n‐type rear‐junction PERT type silicon wafer solar cells

n‐type silicon wafer solar cells are receiving increasing attention for industrial application in recent years, such as the n‐type rear‐junction Passivated Emitter Rear Totally‐diffused (PERT) solar cells. One of the main challenges in fabricating the n‐PERT solar cells is the opening of the rear dielectric for localized contacts. In this work laser ablation is applied to locally ablate the rear dielectric. We investigate the laser damage to the emitter at the laser‐ablated regions using the emitter saturation current density, J_0e,laser, extracted by two approaches. J_0e,laser is observed to be injection dependent due to high J₀₂ recombination caused by laser damage to the space charge region. By using the optimized laser ablation parameters, n‐PERT solar cells with an efficiency of up to 21.0% are realized. Copyright © 2015 John Wiley & Sons, Ltd.     

Electron‐beam crystallized large grained silicon solar cell on glass substrate

Thin film hetero‐emitter solar cells with large‐grained poly‐silicon absorbers of around 10 µm thickness have been prepared on glass. The basis of the cell concept is electron‐beam‐crystallization of an amorphous or nanocrystalline silicon layer deposited onto a SiC:B layer. The SiC:B layer covers a commercially well available glass substrate, serving as diffusion barrier, contact layer and dopand source. For silicon absorber deposition a low pressure chemical vapour deposition was used. The successively applied e‐beam crystallization process creates poly‐silicon layers with grain sizes up to 1 × 10 mm² with low defect densities. The high electronic quality of the absorber is reflected in open circuit voltages as high as 545 mV, which are realized making use of the well‐developed a‐Si:H hetero‐emitter technology. Copyright © 2011 John Wiley & Sons, Ltd.     

Wire bonding as a cell interconnection technique for polycrystalline silicon thin‐film solar cells on glass

The interconnection of solar cells is a critical part of photovoltaic module fabrication. In this paper, a high‐yield, low‐cost method for interconnecting polycrystalline silicon thin‐film solar cells on glass is presented. The method consists of forming adjacent, electrically isolated groves across the cells using laser scribing, and then forming wire bonds over each laser scribe, resulting in series interconnection of the individual solar cells. Wire bonds are also used to connect the first and last solar cell in the string to external (tabbing) leads, forming a mini‐module. A layer of white paint is then applied, which acts as both an encapsulation layer and an additional back surface reflector. Using this method, an 8·3% efficient mini‐module has been fabricated. By exploiting recent developments in wire bonding technology, it appears that this process can be automated and will be capable of forming solar cell interconnections on large‐area modules within relatively short processing times (∼10 min for a 1 m² module). Copyright © 2010 John Wiley & Sons, Ltd.