【作者】 李中兰；

【导师】 杨德仁； 余学功；

【作者基本信息】 浙江大学 ， 材料物理与化学， 2010， 硕士

【摘要】 光伏发电技术是解决能源危机的有效途径之一,而用于光伏发电的太阳电池目前大多数是由晶体硅材料制备的。在硅太阳电池的成本中,硅材料占据很大的比例。由于降低成本的要求,晶硅太阳电池正朝着薄片化趋势发展。但是,随着硅片厚度的减薄,机械性能弱化,破碎率提高,电池片弯曲严重,这将严重影响太阳电池的成品率。因此,研究晶体硅材料的机械性能并采取合适的工艺来减小硅片机械强度的降低是目前国际光伏界关注的热点之一。本论文立足于晶体硅材料的机械性能,主要研究内容如下:(1)研究锗掺杂对铸造多晶硅材料的室温断裂强度的影响,并分析了其机理。结果表明锗杂质能够显著提高铸造多晶硅的机械性能,在损伤层完全去除的情况下,掺锗多晶硅的断裂强度比普通多晶硅提高16-21%;在磷扩散后掺锗硅片的断裂强度仍高于普通样品。因此,高强度的掺锗多晶硅在将来薄片太阳电池上具有很好的应用前景。(2)研究了高温下多晶硅中位错滑移与晶界的相互作用关系,初步探讨了晶界对机械性能的影响行为。结果表明晶界具有阻止位错滑移的作用,位错滑移到晶界时很难穿越晶界壁垒。而晶界本身对材料的杨氏模量和硬度等机械性能参数具有负面影响,晶界处的杨氏模量与硬度均小于晶粒内。(3)研究了太阳电池工艺中硅材料机械性能的演变,以及采用合理的太阳电池背电极花样来提高其机械性能。结果表明,在太阳电池的制备工艺中,损伤层的去除、绒面制备以及氮化硅减反射层的生长都有利于提高前段工序后的断裂强度,而磷扩散和前后电极与铝背场的印刷与烧结则会对机械性能产生不利影响。背电极花样对太阳电池的断裂强度有明显的影响,通过改进背电极花样能够有效地提高太阳电池的机械性能,降低其破碎率。总的来说,以上这些研究结果对于新型高强度的掺锗太阳电池的实际应用提供了一定的科学依据,同时进一步加深了我们对于多晶硅中位错与晶界相互作用机制的理解,而且对电池工艺过程中控制电池机械性能提供了必要的技术支持。更多还原

【Abstract】 Photovoltaic （PV） industry is globally booming due to the energy resource crisis, and the silicon solar cells used for optical-to-electrical conversion are the main products on the PV market. However, the bottle-neck restricting the wide application of silicon solar cell is still its high cost, among which the silicon material is a main cost item. Therefore, the silicon solar cell tends to become thinner and thinner in order to save the consumable material. But, thinning the wafer will cause the degradation of mechanical strength and the increase of breakage and warpage. These are very detrimental for the performance and yield of silicon solar cell. Thus, it is significantly necessary to investigate the mechanical properties of thin wafer and find an optimum way to reduce the mechanical strength degradation of thin wafer.This dissertation is focused on the mechanical properties of crystalline silicon solar cell, including the following aspects,（1） The effect of germanium doping on the mechanical properties of cast multicrystalline silicon has been investigated. It is found that the germanium can significantly enhance the mechanical strength of silicon material by 16-21%, compared to the conventional ones. This enhance effect can also be found after the phosphorus diffusion technology. It implies that germanium-doped silicon with strong mechanical strength is a promising substrate for thin solar cell.（2） The dislocation slip near grain boundary （GB） and the effect of GBs on the mechanical property of silicon have been investigated. It is found that the GB can cause a barrier for the slipping of dislocation, and therefore the dislocation cannot slip through the GB. Meanwhile, the GB can reduce on the characteristic parameters of silicon mechanical properties to some extent, such as young’s modulus and hardness. The young’s modulus and hardness at the GBs are averagely smaller than those in the grains.（3） The evolution of mechanical property during cell fabrication is studied. It is found that the texturing and Si₃N₄ film deposition can improve the wafer fracture strength, while the phosphorus diffusion, screen printing and metal contacts firing will decrease the fracture strength. The mechanical strength of solar cell can be effectively improved by modifying the busbar pattern on the rear. In summary, the achievements in this dissertation have supplies the necessary science understanding and technology support for the practical application of germanium-doped silicon solar cell on the mechanical properties, the interaction of dislocations with the GBs and the evolution of mechanical strength in the process of cell fabrication.更多还原