| Summary: | In this paper, the cylindrical, conical and parabolic nanostructures inherited from self-organized anodic aluminum oxide (AAO) are applied to silicon-based ultra-thin solar cells aiming for a new design concept for low-cost, high-efficiency double-grating solar cells. Numerical results reveal that the optimal bottom metal grating can enhance the absorption capacity of ultra-thin solar cell at 0.5 µm–1.1 µm waveband with a very small parasitic absorption. Meanwhile the surface grating with a period of 0.1 µm can strongly enhance the absorption of solar cell in 0.3 µm–0.5 µm waveband. Consequently, the silicon-based ultra-thin solar cell inherited their characteristics very well when both the optimal silicon surface grating and bottom metal grating are applied at the same time, thereby increasing the absorption rate of the solar cell in the entire waveband. Compared to the solar cell with single surface grating and the one with single bottom metal grating, the photocurrent density increments of the double-grating nanostructured solar cells can reach as high as 75.47% and 40.69%, respectively. Further results show that the conical and parabolic nanostructured gratings have higher light absorption efficiency and lower structure morphology-dependent sensitivity than the cylindrical nanostructured one, which is more conducive to the application of high efficiency ultra-thin solar cells.
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