German analysis institute Fraunhofer ISE has unveiled a brand new metallization course of for heterojunction photo voltaic cells that reportedly will increase energy conversion efficiencies by greater than 0.1% whereas lowering silver consumption. A tool constructed utilizing the brand new method achieved an effectivity of 23.2%.
Researchers from Germany’s Fraunhofer Institute for Solar Energy Systems (Fraunhofer ISE) have optimized the front-side metallization of silicon heterojunction (SHJ) photo voltaic cells utilizing very low silver laydown for multi-wire interconnection.
“This methodology is simple to implement as a result of it solely requires using sufficiently nice line screens together with an optimized grid structure,” stated corresponding writer Andreas Lorenz. pv journal.
To optimize the metallization course of, the researchers took under consideration three manufacturing parameters – the printing method, the pitch of the finger, and the width of the finger. “One of the principle challenges for the approaching years is the rising scarcity of important assets, particularly, silver, indium, and bismuth,” stated the analysis group. “The want to cut back silver laydown is especially pressing for SHJ photo voltaic cells as a result of silver paste is usually used on the back and front sides of typical cell architectures.”
In their work, the scientists investigated using silver solely on the entrance aspect. First, they examined knotless versus customary printing screens. In the primary case, they used a complicated knotless fine-mesh display generally known as 520 X 11 X 0°, and within the second, a traditional angled fine-mesh display generally known as 520 X 11 X 22.5°.
“The entrance aspect metallization is display printed utilizing two display varieties with the identical printing situations and a printing/flooding velocity of print/flood = 300 mm/s,” they added, saying that the knotless methodology obtained a imply finger width narrower than 1.3 μm in comparison with the usual methodology.
Regarding the pitch of the silver fingers, the group examined a silver finger pitch of 1.3 mm, which resulted in 120 fingers, and a 1 mm pitch, which resulted in 156 fingers. In the case of 1.3 pitch, a complete of 19 mg of silver paste was required, whereas within the case of 1 mm, it elevated to 21 mg.
“Decreasing the pitch of the finger leads to an elevated fill issue (FF), whereas the short-circuit present density decreases because of elevated shading,” the lecturers say. Both results offset one another to a big extent on this particular case, leading to an equal conversion effectivity for each teams.
In addition, the researchers examined three finger widths – 20 μm, 18 μm, and 15 μm. In doing so, they discovered it doable to print a flat grid structure with a width of 15 μm, leading to a silver discount of 5 mg in comparison with 20 μm, along with an elevated effectivity of 0.14%
Following this optimization methodology, the group produced optimized photo voltaic cells with a complicated knotless fine-mesh display 520 X 11 X 0 °, with a finger itch of 1 mm and a width of 15 µm. Those in comparison with non-optimized cells, utilizing the standard angled fine-mesh display 520 X 11 X 22.5 °, with a finger itch of 1.3 mm and a width of 20 μm.
“The optimized group obtained a mean conversion effectivity of 23.2%, which corresponds to a achieve of 0.17% in comparison with the reference cells with out the described optimization,” they concluded. “Furthermore, the silver paste positioned on this group may be lowered to ~ 2 mg. This emphasizes the significance of fixed optimization of the display printing course of by way of cell manufacturing and useful resource use for SHJ photo voltaic cells.
Their findings are introduced in “Towards a cutting-edge metallization course of for silicon heterojunction photo voltaic cells with very low silver laydown,” printed in Advances in Photovoltaics. The analysis group consists of scientists from the German digital part firm Yageo Nexensos GmbH.
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