氢化非晶硅薄膜局域结构特征及其形成的分子动力学模拟研究

氢化非晶硅(a-Si:H)薄膜是非晶硅/晶体硅异质结(HIT)太阳电池的核心薄层，其质量直接决定了该电池的光电转换效率。实验研究发现该电池的制备工艺与性能之间关系复杂，重复性差，原因就是对a-Si:H薄膜的微观结构及其形成机制还缺乏认识。本项目拟运用分子动力学方法模拟a-Si:H薄膜在晶体硅表面的生长，考察沉积条件对a-Si:H薄膜结构形成的影响，包括沉积基团及其入射、生长速率、硅衬底表面和温度等；并对a-Si:H薄膜局域结构进行特征化分析，具体包括悬挂键、HA键型指数、Voronoi多面体和原子团簇类型等分析。以期得到晶体硅表面a-Si:H膜局域结构形成和演变的原子机制，以及工艺条件与a-Si:H薄膜局域结构之间的本质关联，架起工艺与性能之间的微结构桥梁。本项目研究对于HIT型太阳电池制造技术的开发与产业化将具有重要指导意义，对于非晶材料结构的认识与表征这一重要科学领域也将作出一定贡献。

The hydrogenated amorphous silicon (a-Si:H) film is the core structure of HIT (Heterojunction with IntrinsicThinlayer) solar cell. Its quality determinates the photoelectric conversion efficiency of HIT solar cell directly. Experimental studies have shown that the relationship between the process parameters and the cell performance is intricate and lacks of repetition. One of the key reasons is that it is a poor understanding of the structure characteristics and its formation mechanism of hydrogenated amorphous silicon films. In the present project, molecular dynamics simulations on the growth of the a-Si:H films on crystalline Si surfaces will be carried out. The following major factors that affect the structures of a-Si:H films will be investigated: deposit radicals; incident velocities, frequencies and angle ranges; Surface orientation, surface smoothness and temperatures of crystalline Si substrate. The local microstructure of a-Si:H film will be characterized by the methods of bond types, atomic clusters and polyhedron analysis: mainly including the silicon dangling bond, Si-H to Si-Hx, the Honeycutt-Anderson (HA) bond pair analysis, the Cluster-Type Index Method (CTIM), the Atomic Cluster Alignment Method (ACAM) and the Voronoi polyhedron analysis (VP). We expect to understand the atomic mechanism of the characterization local structures formation and evolution of the a-Si:H films on crystalline Si surfaces and the intrinsic relationships between the process conditions and the characterization local structures of a-Si:H films. The expected results will present important references for the manufacture technology research, developing and industrialization of the HIT solar cell, and will contribute greatly to the understanding and characterization of amorphous structure, which is also an important scientific field.