Mechanical Stacking Multi Junction Solar Cells Using Transparent Conductive Adhesive

We report a mechanical stacking technology with transparent conductive adhesive as intermediate conductive layer for multi-junction-solar cells. Transparent adhesive jell dispersed with Indium-Tin-Oxide (ITO) particles ranging from 5 to 10 wt% was developed for stacking solar cell substrates. A connecting resistivity below 2.0 Ωcm2 was achieved in a condition of solidifying the adhesive gel under a gas pressure from 4.0x105 to 7.0x105 Pa. The connecting resistivity was kept lower than 3.0 Ωcm2 when samples was exposed at a high temperature at 80oC and a high humidity of 85% humidity atmosphere in the case of solidification pressure at 7.0x105 Pa. The low connecting resistivity give a possibility of application our conductive adhesive to solar cell with an effective efficiency higher than 30%. Stacked solar cells was successfully achieved by pasting a InGaP/GaAs thin film epitaxial layer to a Ge solar cell using our intermediate adhesive layer.