Multijunction amorphous silicon alloy‐based solar cells and modules offer the potential of obtaining high efficiency with long‐term stability against light‐induced degradation. We have studied the stability of the component cells of the multijunction devices prepared under different deposition conditions. We observe a definite correlation between the microstructure of the intrinsic material and initial and light‐degraded performance of the cells. Using suitable deposition conditions and optimum matching of the component cells, we have fabricated double‐junction dual‐bandgap cells which show stabilized active‐area efficiency of 11% after 600 hours of one‐sun illumination at 50 °C. Double‐junction and triple‐junction modules of 900 cm2area have been fabricated, and the performance of these panels will be discussed.