Advanced Metallization Concepts by Inkjet Printing

Abstract

In the highly competitive photovoltaics market, manufacturers of solar cells and modules are under constant pressure to reduce the cost per Wp. One of the main cost drivers of crystalline silicon based solar cells is the front-grid metallization; this front-grid usually consists of screen-printed fingers and busbars. The multi-busbar solution, SmartWire Connection Technology (SWCT), as developed within the Meyer Burger group, offers a significant reduction in silver consumption by replacing the screen-printed busbars by coated copper wires embedded in a foil. A further reduction in silver consumption is realized by replacing the screen-printed fingers with inkjet printed fingers. By inkjet printing a silver nanoparticle ink, fingers are made with a width <35 μm and a thickness of a few micrometer, therefore reducing the silver consumption to <10 mg. This combination of inkjet printed front-grid fingers with SWCT is applicable for all cell types and concepts (mc-Si, Cz-Si, PERC, Heterojunction, etc.). For front-grid metallization without any silver, a combination of an inkjet printed mask with Ni-Cu plating is used. With this process flow, finger widths <20 μm are obtained. Ni-Cu plated heterojunction solar cells were made with record efficiencies of 22.3% for 5inch and 21.7% for 6inch Cz-Si cells. Based on cost of ownership calculations, one critical parameter is the consumption of masking ink. By improving the print strategy, the consumption of masking ink is reduced by > 70% which even further improves the total cost of ownership.