Next-generation High Efficiency and Low Cost GaAs/Si Multijunction Solar Cells with Smart Stack Technology

Multi-junction (MJ) solar cells have a practical solution to consist with high efficiency and low cost. This paper shows the demonstrations of a GaAs/Si MJ solar cells with mechanical stacking method. Our key technology is the direct bonding using conductive nanoparticle alignment, which is named “Smart Stack” technology. Using this technology, we fabricated an InGaP/GaAs/Si 3-junction solar cell and observed the efficiency of 24.71% (AM1.5g). According to our theoretical prediction, these efficiencies can be improved over 30% under the optimized structure design. In addition, we examined the cost analysis of the GaAs/Si MJ module. Under the low concentration, the cost attains the competitive level (module cost with lens_ <0.4$/W). The obtained results show the possibility of GaAs/ Si MJ solar cells as next generation solar cell.