Be able to use characterisation measurements to help guide the optimisation of a metallisation process.Be able to optimise a screen printing process by varying mesh density, strand diameter, emulsion thicknesses and printing parameters.Understand the process of forming a metal grid on the front surface of a screen-printed solar cell.Understand what is critical for the formation of a back surface field and rear electrode for a screen-printed solar cell.This tutorial focuses on the silver screen printing process as the design of the screens is critical for the way the pattern is used to form the metal grid. When the cell is cofired (in the next production step), the paste etches through the silicon nitride and silver contacts the underlying silicon to form the n-type contacts to the solar cell. Screen printing is used to form the rear aluminium electrode and the front surface silver grid (busbars and fingers) on the silicon nitride antireflection coating (ARC). The paste can be pushed through the openings in the screen using a squeegee to form a pattern of paste on the cell surface under the screen. The non-irradiated regions can then be washed away by spraying the screen with water leaving openings in the emulsion. When the screen is irradiated according to the pattern, the irradiated emulsion hardens and binds to the screen. The pattern is formed in a polymer, called an emulsion, which is sensitive to light. Screen-printing is a way of depositing a material (e.g., paste) on a surface according to a pattern formed in a screen comprising a network of meshed wires or strands.
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