|Front-side metallization with high aspect ratio by stencil printing for crystal Si solar cell|
|Chien-Ming Chen, Yu-Chia Liao, Wei-Ming Su, Po-Sheng Huang, Li-Wei Cheng
TOPCELL SOLAR INTERNATIONAL CO. LTD, Taoyuan, Taiwan
In order to reduce shading loss and keep low Rs under fine-line printing process, front-side metallization with high aspect ratio is necessary. In this paper, stencil screen with several opening widths are compared with mesh screen. While opening width in mesh screen is confined to about <40um, cells with high series resistance are generated because of the low cross section area of the finger. Nevertheless, stencil printing with 100% open areas could raise the aspect ratio in fine-line printing and effectively improve finger uniformity, leading to lower series resistance. In this work, fingers with aspect ratio over 0.5 have been achieved by stencil printing and kept low width. On the other hand, five pastes with different viscosity are applied to optimize stencil printing for 35μm and 45μm opening width respectively. The paste with higher viscosity has larger aspect ratio but poor printing quality. Finally, through line resistance measurement, larger aspect ratio performed by stencil printing actually exhibits lower resistance than that by mesh printing, making stencil suitable in fine-line printing production. With stencil printing for only fingers, followed by mesh printing of the busbars, +0.06% efficiency gain was achieved compared with single mesh printing as the result of the low resistance and high FF.