【作者】 王成龙；

【导师】 范多旺；

【作者基本信息】 兰州交通大学 ， 交通信息工程及控制， 2009， 博士

【摘要】 由于能源和环境问题,太阳能光伏发电技术重新得到了人们的关注。高效、稳定的晶体硅太阳能电池由于硅材料生产过程的高能耗和重污染,使得硅晶体太阳能电池应用成本居高不下,急需替代技术。多晶硅薄膜太阳能电池无论从电学性能还是制造成本,无疑都成为最具潜力的太阳能电池制造技术。本文研究了用于太阳能电池用多晶硅薄膜的制备技术,着重研究了极具潜力的多晶硅薄膜制备方法,铝诱导晶化（AIC）法。本文利用直流磁控溅射技术制备了glass/Al/a-Si叠层结构,通过铝诱导晶化（AIC）的方法制备了多晶硅薄膜（poly-Si thin film）,系统研究了各种工艺参数对制备多晶硅薄膜结构、性能的影响以及薄膜晶化过程的影响;理论研究了铝诱导晶化机制——铝诱导层交换（ALILE）的初始过程;重点探索了无需后续退火处理的AIC法和低掺杂率多晶硅薄膜的制备方法。主要研究结果如下:1、系统研究了各种工艺参数对制备多晶硅薄膜结构、性能的影响以及薄膜晶化过程的影响。实验结果表明:退火温度、时间、铝膜厚度、退火气氛的种类以及衬底形貌对AIC晶化过程具有复合的影响,为了得到电学性能优良的多晶硅薄膜,需要优化组合上述参数。2、用数学模型描述了铝诱导晶化机制:铝诱导层交换（ALILE）过程中非晶硅原子向铝层扩散（stepl）和在铝层中成核（step2）的动力学过程,在这个模型的框架下,对成核之前铝层中硅原子的浓度随时间的变化和成核时间进行了深入研究。研究结果表明:a-Si溶解到铝膜中的激活能E_A为0.57 eV,利用该模型能够很好的解释铝诱导晶化法能够使非晶硅（a-Si）在低温（＜577℃）下实现晶化的原因。3、用直流磁控溅射外加偏压电场的方法,在铝膜上制备了glass/Al/Si薄膜。实验结果表明:在AIC非晶硅制备多晶硅薄膜过程中,通过外加偏压电场的方法,显著降低了AIC制备多晶硅薄膜的温度（＜100℃）,在无需后续退火的条件下制备了高晶化率（晶化率＞90%）的多晶硅薄膜。4、在AIC过程中,在不同的退火温度和温度模式下对glass/Al/a-Si进行了退火处理,制备了多晶硅薄膜,并对其铝掺杂浓度和Hall迁移率进行了表征。实验结果表明:通过非晶硅的QCGE AIC（硅原子的快速扩散Q;冷却成核C;晶粒的慢速生长G;铝原子的向外扩散E,QCGE）制备的多晶硅薄膜具有较低的铝掺杂率(2.0x10¹⁶cm^-3),霍尔测量表明,多晶硅薄膜中铝掺杂浓度依赖于制备过程中的退火温度和退火模式。为通过AIC制备多晶硅薄膜过程中降低铝掺杂浓度提供了新的思路。更多还原

【Abstract】 With the concept of sustainable development and environmental protection deeply rooting among the people and gradual exhaustion of ordinary petrifaction energy sources,photovoltage（PV）technology is gaining increasing interest again. Crystallization silicon（c-Si）solar cells,with high efficiency and stable performance, starve for the substitute technology due to the expensive cost and hard pollution for fabrication of silicon wafer.Poly-Si thin-film solar cells maybe one of an alternative and promising way to reduce cost of solar cell of silicon wafer.The theses emphasize the fabrication technology of polycrystalline thin-films of solar cell,and make research on the aluminum-induced crystallization（AIC）,a promising preparation method for poly-Si thin-film at low temperature.Glass/Al/a-Si composite layer was deposited using dc-magnetron sputtering,and fabricated the poly-Si thin-film by AIC;studied the influence of process parameters on structure and performance of poly-Si thin film;the initial stage of the aluminium-induced layer-exchange（ALILE）process was studied theoretically; decreasing the annealing temperature for AIC and a route to getting low Al dopant concentration poly-Si thin film were focused on.1、The experiments of aliminmum-induced crystallization of amouphous silicon were systemly studied.We have done a series of experiments to discuss the influcence of experimental parameters such as annealing teimperature,annealing time,and thickness of aluminmum films,buffer layer（Al₂O₃）,annealing atmosphere,and fabric of substrate.The results showed that,that parameters are play a mulriple role in annealing process and properties of fabricated poly-Si films.So,for getting a high electronic quality poly-Si thin films,above parameters should be optimized and fitted together.2、The initial stage of the aluminium-induced layer-exchange（ALILE）process is studied theoretically.The diffusion of silicon atoms from an amorphous Si layer into an Al layer through a buffer layer（Al₂O₃）prior to Si grain nucleation within the Al layer is considered.A kinetic model is devoted to describe this process.Based on the framework of this model,the evolution of the Si concentration within the Al layer prior to Si grain nucleation and the nucleation time are investigated for different annealing temperatures and preparation conditions of the buffer layer.From the comparison of results of calculations with experimental data,the activation energy （E_A）of 0.57 eV for a-Si atom diffusion into Al film was determined,which maybe the reason for crystallization of a-Si at low temperature（＜577℃）by AIC.3、Polycrystalline silicon（poly-Si）thin-film is fabricated on Al-coated planar glass substrates at the temperature below 100℃,using AIC amorphous silicon（a-Si） deposited by dc-magnetron sputtering under an electric field.The properties of NA poly-Si films（AIC of dc-magnetron sputtered silicon non-annealing）are characterized by Raman spectroscopy and x-ray diffraction（XRD）spectroscopy.A narrow and symmetrical Raman peak at a wave number of about 521 cm^-1is observed for samples,showing that the films are fully crystallized.XRD spectra reveal that the films are preferentially（111）oriented.Furthermore,the XRD spectrum of the sample prepared without electric field does not show any XRD peaks for poly-Si,which only appears at about 38°for Al（111）orientation.It is indicated that the electric field plays an important role in crystallization of poly-Si during the dc-magnetron sputtering.Thus,high quality poly-Si film can be obtainedat low temperature and separate post-deposition step of AIC of a-silicon can be avoided.24、Typically,highly p-doped(2×10¹⁸cm^-3)poly-Si films fabricated by the aluminuminduced layer exchange（ALILE）process are not suitable as solar cell absorber layers.In the thesis,the fabrication of high-quality,continuous polycrystalline silicon（poly-Si）films with lower doping concentrations(2×10¹⁶cm^-3) using AIC is reported.Secondary-ion-mass spectroscopy（SIMS）results show that annealing at different temperature profiles leads to a variety of Al concentrations.Hall Effect measurements revealed that Al dopant concentration depends on the annealing temperature and temperature profile.Raman spectral analysis revealed that samples prepared via AIC contain some regions with small grains.更多还原