Si結晶太陽電池における高精細スクリーン印刷の最新動向

抄録

Screen printing for solar cells has continued to evolve rapidly. The Ag paste used for printing the front side of a solar cell requires both fine-line and fire-through control. It is necessary to thoroughly understand this control to improve cell efficiency. A "shallow emitter" is one of the high-performance solar cell technologies. To fabricate a shallow emitter cells, it is necessary to optimize the next generation of screen printing. A shallow emitter requires an increase in the finger number, fine lines to decrease the shadow loss, and a high screen mesh. We have been able to achieve a resolution finer than 50 μm for finger lines of screen printing on a solar cell wafer using a properly tuned combination of an ultra-high mesh and a new lead-free Ag paste. For every target line width from mass production to the next generation, there are three steps (50⁄40⁄30 μ m).We propose the idea of screen spec, which provides good fine-line printing. In addition to ultra-fine lines, the new lead-free Ag paste is potentially capable of being adapted for use with values greater 100 Ω⁄□ for high sheet resistance cells (∼120 Ω⁄□).We recently obtained part of the solution for 30-μm line screen printing, which will make a 120 Ω⁄□ cell available for fabricating high performance solar cells. The end goal requires the "total optimization of the solar cell process," not just individual improvements.