高效多晶硅中Σ3晶界复合活性的研究
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摘要
多晶硅作为一种基础的光伏材料,近年来受到诸多关注。多晶硅中存在着许多缺陷如位错、晶界等,不利于多晶硅太阳能电池的转换效率。而且并非所有多晶硅中的晶界都形成深的复合中心,阻碍载流子的扩散。采用电子束诱生电流(Electron Beam-Induced Current,EBIC)技术和电子背散射衍射(Electron Backscatter Diffraction,EBSD)技术对商业化生产的原生高效多晶硅中的特殊晶界(CSL晶界)进行研究,探究它们的复合活性。结果表明,孪晶上的Σ3 (-1-11)晶界几乎没有复合活性,EBIC衬度在300K下为1.32%;而普通晶粒上的Σ3 (1-1-1)晶界表现出了复合特性,300K下的EBIC衬度为39.62%,并且随着温度的降低,出现了缓慢的下降,说明Σ3 (1-1-1)晶界处形成了深能级复合中心。
As a basic photovoltaic material,polysilicon(poly-Si)has attracted many attentions in recent years.There are many defects such as dislocation and grain boundary(GB)in polysilicon,which is unfavorable to the conversion efficiency of poly-Si solar cells.But not all GBs in poly-Si is deep recombination centers,hindering the diffusion of minority carriers.In this study,electron beam induced current(EBIC)and electron back scattering diffraction(EBSD)was used for the special GBs(CSL GBs)in commercial production of high efficiency polysilicon,and the recombination of CSL GBs was researched.The results showed that the Σ3(1-11)GB at twin grain has almost no recombination activity,and EBIC contrast is 1.32% with the temperature of 300 K.While Σ3(1-1-1)GB at normal grain showed the recombination activity,the EBIC contrast is 39.62% with the temperature of 300 K.And with the decrease of temperature,there is a slow decline,indicating that a deep-level recombination center has formed at the grain boundary of Σ3(1-1-1).
As a basic photovoltaic material,polysilicon(poly-Si)has attracted many attentions in recent years.There are many defects such as dislocation and grain boundary(GB)in polysilicon,which is unfavorable to the conversion efficiency of poly-Si solar cells.But not all GBs in poly-Si is deep recombination centers,hindering the diffusion of minority carriers.In this study,electron beam induced current(EBIC)and electron back scattering diffraction(EBSD)was used for the special GBs(CSL GBs)in commercial production of high efficiency polysilicon,and the recombination of CSL GBs was researched.The results showed that the Σ3(1-11)GB at twin grain has almost no recombination activity,and EBIC contrast is 1.32% with the temperature of 300 K.While Σ3(1-1-1)GB at normal grain showed the recombination activity,the EBIC contrast is 39.62% with the temperature of 300 K.And with the decrease of temperature,there is a slow decline,indicating that a deep-level recombination center has formed at the grain boundary of Σ3(1-1-1).
引文
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[2]YANG Y M,YU A,HSU B,et al,Development of highperformance multicrystalline silicon for photovoltaic industry,Prog.Photovolt[J].Res.Appl.2015,23:340-351.
[3]SUTTON A P,BALLURRI R W,Interfaces in Crystalline Materials[M].Oxford University Press:Oxford,New York,1995.
[4]陈君.铸造多晶硅晶界电学特性的EBIC研究[D].杭州:浙江大学,2005:29-32.
[5]RANDLE V.The measurement of grain boundary geometry[M].Institute of Physics Publishing,UK:University of Bristol,1993:79-89,33-62.
[6]LIN H K,WU M C,CHEN C W,et al.Evolution of grain structures during directional solidification of silicon wafers[J].Journal of Crystal Growth,2016,439:40-46.
[7]STOFFERS A,MIREDIN O C,SEIFERT W et al.Grain boundary segregation in multicrystalline silicon:correlative characterization by EBSD,EBIC and atom probe tomography[J].Progress of Photovoltaics,2015,23:1742-1753.
[8]GAO N,WANG S C.A comparison of grain size determination by light microscopy and EBSD analysis[J].Journal of Materials Science,2005,0022-2461
[9]MARTIN I B,GREEN A.Investigating polysilicon thin film structural changes during rapid thermal annealing of a thin film crystalline silicon on glass solar cell[J].Mater Sci:Mater Electron,2010,21:994-999.
[10]BEHM T,FUNKE C,MOLLER H J.Surface orientation characterisation of rough mc-silicon surface by confocal microscopy and EBSD[J].Wiley Online Library,2013,45:781-786.
[11]STOKKAN G,HU Y,MJOS O,et al.Study of evolution of dislocation clusters in high performance multicrystalline silicon[J].Solar Energy Material&Solar Cells,2014,130:670-685.
[12]KUSANAHI S,SEKIGUCHI T B,SHEN B,et al.Electrical activity of extended defects and gettering of metallic impurities in silicon[J].Material Science&Technology,1995,11(11):682-690.
[13]杨德仁.半导体材料测试与分析[M].北京:科学出版社,2010:309.
[14]WANG Z J,SUREKAWA S T,IKEDA K,et al.Relationship between electrical activity and grain boundary structural configuration in polycrystalline Silicon[J].I S,1999,7:197-205.
[15]SAWADA H,ICHINOSE H.Structure of{112}Σ3.Scripta Mater,2001,44:2327-2330.