Formation of CuInSe2 and CuGaSe2 Thin Films Deposited by Three-Stage Thermal Co-Evaporation: A Real-Time X-Ray Diffraction and Fluorescence Study
Formation of CuInSe2 and CuGaSe2 Thin Films Deposited by Three-Stage Thermal Co-Evaporation: A Real-Time X-Ray Diffraction and Fluorescence Study
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DOI：
10.1002/aenm.201300339
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发表时间：
2013-10-01
影响因子：
27.8
通讯作者：
Mainz, Roland
中科院分区：
文献类型：
--
作者：
Rodriguez-Alvarez, Humberto;Weber, Alfons;Mainz, Roland
基于共蒸发Cu（In，Ga）Se-2吸收膜的薄膜太阳能电池在当前多晶薄膜技术中呈现最高的效率。由于开发了一种用于原位生长研究的新型实验装置，因此有可能第一次在这种沉积过程中跟踪晶相的形成。这种基于同步加速器的能量色散X射线衍射和荧光装置适用于薄膜气相沉积过程的实时研究。通过对三阶段法制备的CuInSe_2和CuGaSe_2晶体的生长研究，发现Cu-In-Se系统的相变符合文献报道的In_2Se_3-Cu_2Se赝二元相图。这需要在将Cu-Se掺入第一工艺阶段的In 2Se 3前体膜期间Se亚晶格发生转变。在Cu-Ga-Se系统中，除了晶格间距的增加，我们没有观察到Se亚晶格的转变。此外，保持Ga-Se前体膜的结构缺陷，直到达到CuGaSe 2化学计量。通过对荧光信号的模型计算，我们证实在两个系统中，Cu 2Se在接近25 at.%浓度的表面处的偏析Cu的薄膜再结晶后不久。模型还表明，Cu 2Se渗透到CuInSe 2膜，而它仍然在CuGaSe 2膜的表面。
Thin film solar cells based on co-evaporated Cu(In,Ga)Se-2 absorber films present the highest efficiencies among current polycrystalline thin-film technologies. Thanks to the development of a novel experimental setup for in situ growth studies, it was possible to follow the formation of the crystalline phases during such deposition processes for the first time. This synchrotron-based energy-dispersive X-ray diffraction and fluorescence setup is suited for real-time studies of thin film vapor deposition processes. Focusing on the growth of CuInSe2 and CuGaSe2 fabricated by three-stage processing, we find that the phase transitions in the Cu-In-Se system follow the reported pseudo-binary In2Se3-Cu2Se phase diagram. This requires a transformation of the Se sublattice during the incorporation of Cu-Se into the In2Se3 precursor film from the first process stage. In the Cu-Ga-Se system, besides an increase in the lattice spacings, we observe no transformation of the Se sublattice. Furthermore, the structural defects of the Ga-Se precursor film are preserved until the CuGaSe2 stoichiometry is reached. By means of model calculations of the fluorescence signals, we confirm in both systems the segregation of Cu2Se at the surface near a concentration of 25 at.% Cu shortly after the recrystallization of the films. The modeling also reveals that Cu2Se penetrates into the CuInSe2 film, whereas it remains at the surface of the CuGaSe2 film.