溶液PH值对CdS薄膜结构特性的影响

Influence of solution PHvalue on structural properties of CdS thin films

采用化学水浴沉积(CBD)工艺在玻璃衬底上制备CdS薄膜,研究溶液PH值对CdS薄膜结构特性的影响。薄膜的厚度、组份、晶相结构和表观形貌分别由台阶仪、X射线荧光光谱(XRF)、X射线衍射(XRD)和场发射扫描电子显微镜(FESEM)来表征。溶液的PH值为11.26、11.37和11.48时,CdS薄膜的晶相以六方相为主,薄膜的厚度先增大后减小;PH值为11.62、11.66时,薄膜的晶相以立方相为主,薄膜的厚度进一步减小。同时,随着溶液PH值增大,CdS薄膜的晶格常数也逐渐增大。两种晶相的CdS薄膜缓冲层与CIGS薄膜分别构成异质对形成异质结时的晶格失配分别为32.297%和1.419%,界面态密度分别为2.792×1014和8.507×1012,因此高效CIGS薄膜太阳电池更需要立方相的CdS薄膜。

In this article,CdS thin films were deposited on glass substrates by chemical ba th deposition （CBD） technique,and the influence of solution PH value on structu ral properties of CdS thin films is researched.The thickness,the composition,the crystal structure and the morphology of the films were measured by step Meter,X-ray diffraction （XRD） and scanning electron microscope （SEM）,respectively.The cryst al phase of CdS thin films is mainly hexagonal phase for smaller PH values （for 11.26, 11.37and 11.48）,and the thickness of the films first increases and then decreases.The crystal phase of CdS thin films is mainly cubic phase for higher PH values （for 11.62and 11.66）, and the thickness of the films is further reduced.The crystal lattices of CdS thin films gradually increase with the inc rease of solution PH values. When the heterojunctions are formed by CIGS thin films and CdS thin films with two different crystal phases n（hexagonal phase and cubic phase）,the crystal mismatches are res pectively 32.297%（hexagonal phase） and 1.419% （cubic phase）,and the interface state dens ities are respectively 2.792×1014 （hexagonal phase） and 8.507×1012 （cubic phase）.Therefor e,it is more necessary to deposit the cubic phase CdS thin films for high efficiency CIGS thin film solar cells.