Li Weimin, Yan Xia, Aberle Armin G, Venkataraj Selvaraj
Solar Energy Research Institute of Singapore, National University of Singapore, Singapore, 117574, Singapore.
Department of Electrical and Computer Engineering, National University of Singapore, Singapore, 117576, Singapore.
Sci Rep. 2019 Feb 25;9(1):2637. doi: 10.1038/s41598-019-39283-2.
The influence of Na diffusion from various glass substrates during a high-temperature slenization process on the microstructure and morphology of two-step formed CIGS absorber layers is investigated. In order to minimise the CIGS absorber formation time, elemental Se vapour is used to prepare the CIGS absorber. The grain sizes of the CIGS films are found to increase with increasing sodium in the glass substrates (extra clear glass, soda-lime glass, borosilicate glass). TiN and SiN thin films are used as diffusion barrier layers inserted between the glass substrate and the Mo rear conatct to tune the Na diffusion from the soda-lime glass. The interdiffusion between the In-rich CuInSe surface layer and the Ga-rich CuGaSe layer is promoted by the barrier layer, leading to larger CIGS grains. Efforts are also taken to understand the differences in Na diffusion (from the glass substrates) and their effects on the MoSe intermediate layer formation during the high-temperature CIGS absorber formation processes. We find that excess amounts of Na and Se are essential for the MoSe growth. The excessive Na in the form of NaSe at the CIGS/Mo interface works as a Se source and catalyses the MoSe formation. The Se flow in the two-step CIGS formation process must be sufficiently high to obtain high-efficiency CIGS solar cells.
研究了高温硒化过程中各种玻璃衬底中钠的扩散对两步法形成的CIGS吸收层微观结构和形貌的影响。为了缩短CIGS吸收层的形成时间，采用元素硒蒸气制备CIGS吸收层。发现CIGS薄膜的晶粒尺寸随着玻璃衬底（超白玻璃、钠钙玻璃、硼硅酸盐玻璃）中钠含量的增加而增大。使用TiN和SiN薄膜作为插入玻璃衬底和Mo背接触之间的扩散阻挡层，以调节钠钙玻璃中的钠扩散。阻挡层促进了富In的CuInSe表面层和富Ga的CuGaSe层之间的相互扩散，导致形成更大的CIGS晶粒。还努力了解钠扩散（来自玻璃衬底）的差异及其在高温CIGS吸收层形成过程中对MoSe中间层形成的影响。我们发现过量的钠和硒对于MoSe的生长至关重要。CIGS/Mo界面处以NaSe形式存在的过量钠充当硒源并催化MoSe的形成。在两步法CIGS形成过程中，硒流必须足够高才能获得高效的CIGS太阳能电池。
