Determination of the effective optical width of screen-printed and aerosol-printed and plated fingers

One main efficiency loss in industrial solar cells is the shading of the cell due to the metal front side contacts. With the aerosol printing technique followed by a light induced plating (LIP) step, not only the geometrical contact is narrowed compared to screen-printed contacts but also the geometry of the finger changes. In this work the optical behaviour of different finger types is analysed with two different measurement methods. The analysis of the finger was carried out with both encapsulated fingers (module) and not encapsulated fingers (cell). The essential parameter for characterising the finger is the effective width which can be reduced drastically compared to the geometrical width due to total internal reflection at the glass-air layer and the direct reflection from the roundish edges of the contact fingers into the cell. This parameter was determined with different methods. The measured values are compared to a theoretical model for an aerosol-printed and plated finger and are in good agreement.