Silicon based multijunction solar cells with wide-gap a-Si1−xCx:H top cell: Experimental and numerical approaches

In this paper, we report on fabrication of a-Si_1-xC_x:H/a-Si:H tandem cells to demonstrate the benefit of fabricated a-Si_1-xC_x:H single cells to be used as the top cell in multijunction structure. Up to now, V_oc as high as 1.87 V (J_sc= 7.07 mA/cm², FF=0.67, η= 8.82%) has been achieved. Furthermore, the performance of triple junction cells with fabricated a-Si_1-xC_x:H as the top cell was estimated through a numerical analysis. It was observed that with the state-of-art a-Si_1-xC_x:H top cell (i-top thickness of 150 nm), a triple cell with an efficiency of 14.2% could be expected, which was comparable to other groups´ results. It was also found that the estimated efficiency could be improved by increasing the thickness of top cell. From these results, we can conclude that the fabricated a-Si_1-xC_x:H single cell is beneficial to be used as the top cell in the multijunction structure.