Design and Implementation of Ink-jet Printed Fine Line Metallization System for Crystalline Silicon Solar Cells

The use of traditional screen printing technology leads to the breakage of silicon substrates. Moreover, such traditional technology is unable to efficiently improve the precision and aspect ration of the fine line mettalization. Based on these issues, ink-jet printing technology is proposed in this study to fabricate the fine line front side metallization, which can directly eject the nano-silver ink onto the silicon substrate. Meanwhile, the ink-jet printed fine line metallization prototype system for crystalline silicon solar cells is designed and implemented. The proposed system, which can fabricate fine lines by one time ink-jet printing, includes a USB high-speed communication module that achieves high-speed communicaiton, and SDRAM memory modules to carry out ping-pong operation to achieve continuous printing. Nozzle complex timing waveforms and drive voltage waveforms, which are generated by field programmable gata array (FPGA) control module drive piezoelectric ceramics, are used to generate uniform droplet streams. The numerical model based on the volume of fluid is established to gain a deeper understanding of the droplet spraying process. The influence between the driving voltage amplitude and droplet size and droplet velocity is also studied and experimentally verified. Experimental results show that when the polycrystalline silicon substrate temperature is under a curing temperature of 80 ℃, the height of the multi-layer fine line increases linearly, with line thickness 0.5 μm for a single pass. Meanwhile, the width of the print line remains at a range of 35 μm~40 μm. When the layers increase to 60 μm~80 μm, the three-dimensional uniform fine line with high aspect ratio topography is achieved.