Pathways and Potentials for III-V on Si Tandem Solar Cells Realized Using a ZnO-Based Transparent Conductive Adhesive
This work presents a new type of transparent conductive adhesive and its electrical and optical properties with regards to an application in III-V on Silicon tandem solar cells. The developed adhesive is based on a doped ZnO and deposited by spray coating. The optical interconnection of the two sub-cells is identified as one of the major challenges due to the reflectance at the bond and possible approaches to reduce the reflectance are investigated by optical simulations. Regarding the electrical interconnection, an ITO-based contact layer reduced the lowest measured connecting resistivity from previously 17 O·cm²  down to 0.12 O·cm². It is shown that the homogeneity of the bond correlates with its conductivity and can be improved by adjusting the glueing process according to the calcination process of the adhesive. Taking both the electrical and optical parameters of the transparent conductive adhesive into account, the efficiency of a triple junction solar cell was estimated.