Kaneka and imec have unveiled silver-free heterojunction silicon solar cells. The results were obtained by applying copper electroplating technology, which was developed by Kaneka based on imec’s existing copper electroplating technology, A conversion efficiency of more than 21% was achieved in 6-inch silicon substrates with an electroplated copper contact grid on top of the transparent conductive oxide layer.
Today, silver screen printing is the technology of choice for the realization of the top grid electrode in heterojunction silicon solar cells. The difficulty of lowering resistivity and thinning the metal line in silver screen printing prevents from achieving high efficiency and low cost. In the presented silver-free approach, the screen-printed silver is replaced by electroplated copper. Formation of top grid electrode with copper-electroplating in hetero-junction silicon solar cells is the world first result. Copper-electroplating is an economical and industry-proven process. This solution not only overcomes the disadvantages of the silver screen printing, but provides advantages such as enabling higher efficiencies and reducing fabrication costs.