铜铟硒薄膜的外延生长和表面重构及其电池性能研究

Surface Reconstruction of Epitaxial CIS Thin Films and Device Performance

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 surface reconstruction of CIS thin films was systematically investigated.Epitaxial CIS thin films with orientations of（220/204）,（001） and（112） were deposited on GaAs（110）,（001）,（111）A and（111）B substrates,respectively,by using a metal-sputtering and Se-evaporation hybrid technique.The main epitaxial relationship was found to be GaAs（110） // CIS（220）,GaAs（001） // CIS（001）,and GaAs（111） // CIS（112）,respectively.The morphological and structural properties of CIS thin films were determined by scanning electron microscope,atomic force microscope and X-ray diffraction.The（220/204） and（001） surfaces of CIS thin films were found to be unstable under the growth conditions.The deposited surfaces were mainly covered by the low-est specific surface-energy（112） facet regardless of its orientation.Sequence of the specific surface-energy for CIS facets was deduced,based on the geometrical analysis of the defects.Solar cells with preferential oriented CIS thin films as absorber layers were fabricated.The（220/204）-oriented film is characterized to have the best photovoltaic performance,which is consistent with the charge transportation and separation preferring along [220] direction.It in-dicates that higher efficiency of CIS thin film solar cells can be expected by enhancing（220/204） orientation through process optimization.