Improved front side metallization for silicon solar cells by direct printing
This work presents a direct printing technology and an enabling tool for forming very fine gridlines with high aspect ratios that improve the front side metallization of silicon solar cells. The parallel printing setup is anticipated to print each cell in two seconds. The conductive gridlines were formed by a one-step non-contact approach at high speeds using a modified standard screen printable paste. The line width is as small as 40µm, and the line thickness is more than 30µm after firing. The front shading area is significantly reduced, and a previous study has demonstrated up to 0.5% absolute cell efficiency increase as compared to the screen-printing process baseline when the same grid pattern was used. Due to further reduction of grid line width, the pitch between each grid line increases, which affects the travel distance of the electrons excited by photon interaction, which affects the fill factor and ultimately the efficiency of the cell. In addition to the previous comparison study of wafers using the same grid pattern, this study investigated the cell performance using a modified gridline pattern that has an increased number of gridlines. The results showed an absolute efficiency increase up to 0.7%. Other electrical attributes of direct printed high aspect ratio gridlines in terms of ISC, VOC, FF and other data are also presented.