在GaAs的(110)、(001)和(111)A、(111)B等极性晶面上, 通过铜铟共溅-硒蒸镀的方法, 分布外延生长出(220/204)、(001)和(112)结晶取向的单晶CIS薄膜. 系统考察了CIS薄膜外延生长的结晶取向和表面微结构, 发现了这些CIS外延薄膜均需表面重构化而形成比表面能低的CIS(112)晶面, 结合晶体结构研究了各种晶面和比表面能的相关性. 通过各种衬底下不同结晶取向的CIS薄膜的太阳能电池组装, 发现当CIS薄膜生长具有(220/204)结晶取向时电池器件性能最好、效率最高, 说明可通过控制CIS薄膜的沉积条件和选用合适取向的衬底, 增加吸收层(220/204)的结晶取向, 从而显著提高CIS薄膜太阳电池的光电性能.
The mechanism of preferential orientation and surfacereconstruction of CIS thin films was systematically investigated. Epitaxial CISthin films with orientations of (220/204), (001) and (112) were deposited onGaAs(110), (001), (111)A and (111)B substrates, respectively, by using ametal-sputtering and Se-evaporation hybrid technique. The main epitaxialrelationship was found to be GaAs(110) // CIS(220), GaAs(001) // CIS(001), and GaAs(111) // CIS(112), respectively. The morphological and structuralproperties of CIS thin films were determined by scanning electron microscope,atomic force microscope and X-ray diffraction. The (220/204) and (001) surfacesof CIS thin films were found to be unstable under the growth conditions. The depositedsurfaces were mainly covered by the lowest specific surface-energy (112) facetregardless of its orientation. Sequence of the specific surface-energy for CISfacets was deduced, based on the geometrical analysis of the defects. Solarcells with preferential oriented CIS thin films as absorber layers werefabricated. The (220/204)-oriented film is characterized to have the best photovoltaicperformance, which is consistent with the charge transportation and separationpreferring along [220] direction. It indicates that higher efficiency of CIS thinfilm solar cells can be expected by enhancing (220/204) orientation through processoptimization.
参考文献
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