高效多晶硅中Σ3晶界复合活性的研究

Study on the recombination activity of Σ3 grain boundary in high efficiency polysilicon

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).