Novel approach for the bonding of III-V on silicon tandem solar cells with a transparent conductive adhesive

The currently used options for the monolithic interconnection of sub-cells in a Si and III-V tandem solar device are direct wafer-bonding or hetero-epitaxy. Both methods are costly and difficult to transfer into an industrial process. This work presents a novel, scalable and cost -efficient process for efficient process for the interconnection of semiconductor substrates by using a transparent conductive oxide (TCO) interlayer. The TCO material is sprayed from a solution onto both sub-cells which are subsequently connected by using a hot press. The resulting bond shows optical absorption below 2% and a connecting resistivity of 2 Ocm². Bonded samples withstood all further processing steps and thereby demonstrated mechanical stability of the bond.