基于椭偏测试法的氢化非晶硅膜钝化机制

Passivation mechanism of hydrogenated amorphous silicon films for HJT solar cell based on ellipsometry analysis

本征非晶硅(a-Si:H)钝化是获得高效非晶硅/晶体硅异质结太阳电池的关键技术之一,但由于非晶硅的结构复杂多变,至今仍无法对其结构与性能的关联进行简洁的线性表征。本研究采用Sinton设备,测试不同工艺制备的双面a-Si:H薄膜钝化的N型单晶硅片的少子寿命,表征a-Si:H对硅片表面的钝化效果,采用椭圆偏振光谱仪测试拟合a-Si:H薄膜的折射率、消光系数、光学带隙等参数,分析它们与钝化效果的关联。发现:介电函数虚部ε2的峰值和薄膜禁带宽度大致呈现线性关系,高频折射率n∞与钝化后少子寿命呈线性关系。因介电函数由材料的能带结构、态密度等结构因素决定,所以ε2峰值与n∞这两个参数有望为非晶硅结构与钝化效果的理解提供新的表征思路,指导工艺的优化改进。

The passivation of intrinsic amorphous silicon(a-Si:H)is one of the key technologies for high-efficiency amorphous silicon/crystalline silicon heterojunction solar cell.However,it is still difficult to carry out a simple linear representation between the structure and performance of a-Si:H films,for the complex and variable structure of the amorphous materials.In this paper,the lifetime of n-type monocrystalline silicon wafers bifacial passivated by a-Si:H thin films(prepared with different parameters)was tested by Sinton WCT-120 to characterize the passivation effect of the films.The refractive index,extinction coefficient and optical bandgap of a-Si:H films were gotten from the analysis of the ellipsometry spectra of the films.It is found that:a)the imaginary peak position of the dielectric function(ε2)and the bandgap of the a-Si:H films are approximately in a linear relationship,b)the high-frequency refractive index n∞of the films is linearly related to the lifetime of the bifacial passivated wafers.Since the dielectric function is direct determined by structural factors of the films,theε2 peak and n∞are expected to be new characterization parameters to understand the relationship of the amorphous silicon structure and its passivation effect,in order to direct the optimization of the process.