半导体多晶薄膜中缺陷的形成与控制动力学

半导体多晶薄膜因工艺相对简单而具有广泛的潜在应用，尤其是作为新一代光电转换材料。其中，铜铟镓硒（CIGS）、CdTe等薄膜性质特殊，可以实现优于其对应单晶的较高太阳电池转换效率，而其中的物理原理仍在深入探讨中。我们认为，电池效率主要取决于各种缺陷在晶粒中的分布。在这些薄膜材料中，特定的表面、晶界的存在有可能对缺陷的形成起到选择性抑制的作用。在本项目中，我们将使用第一性原理计算的方法，以CIGS多晶薄膜为原型，研究沿不同方向的表面、晶界的原子结构及电子结构特征，研究生长环境的变化、杂质（如Na）的存在对诸结构的影响，研究在生长前沿（表面和晶界）的内禀缺陷（如铜空位、铜位上的III族替换元素，以及复合缺陷等）的形成能对晶向、生长环境的依赖等等。最终的目的是发现缺陷形成的动力学理论，以期指导实验有选择地控制缺陷的形成与分布，进一步提高材料的电学性能。

The semiconducting polycrystalline thin films have many potential applications due to the low cost of the fabrication processes, especially for next generation solar cells. The Cu(InGa)Se2 (CIGS)　and CdTe thin films are very special, for the solar cell based on the thin films can have even higher efficiency than that of the coresponding single crystalline one while the mechanism is still unknown and under intense investigation. We propose that with the rich surfaces and grain boundaries in the polycrystalline thin film, the formation of some point defects during growth can be selectively inhibited. In this project,using first principles calculations, taking the CIGS polycrystalline as an example, we will study the atomic and electronic structures of the surfaces, interfaces, and grain boundaries, the dependant of the structures on the growth environment, the formation energies of the intrinsic defects or complex defects at the growth fronts of CIS, CGS, and CIGS. The aim of this project is to find the dynamics of the defect formation and the ways to control it during polycrystalline thin film growth in order to further improve the electric properties of the material.