Day 4 Energy Electrodes
Day4 Energy has developed an electrode to replace the bus bars on the front side of solar cells. Slightly modified cells are needed for this – obviously, they must not have any bus bars. But they must not have aluminum/silver pads on the back side of the cells where the bus bars are normally soldered during the regular cell connection process. The cell manufacturer can very easily eliminate one to two production steps in doing this. But this is necessary to slightly modify the Back Surface Field ( BSF ) as it can now cover the whole surface because no space is needed for the pads.
Therefore, Day4 Energy requires cells with only contact fingers made of silver on the front side. The electrodes the company developed are then placed over those at a 90° angle. These are made of cooper coated in a low melting metal alloy and embedded in a sandwich of adhesive foil and polymeric film. The cooper strings are then connected to one-or-two-sided bus bars and then are placed next to the cell. When connecting several cells in series, they will be connected to the back side of the adjacent cell. The Day4 Energy electrode is processed at a relatively low temperature of under 200° C and should allow for higher cell and module efficiencies.