Shape effect of silicon nitride subwavelength structure on reflectance for silicon solar cells

In this paper, we, for the first time, examine the spectral reflectivity of hemisphere-, cone-, cylinder-, and parabola-shaped silicon nitride (Si ₃N₄) subwavelength structures (SWSs). A multilayer rigorous coupled-wave approach is advanced to evaluate the reflection properties of Si₃N₄ SWSs. We optimize the aforementioned four different shapes of SWSs in terms of effective reflectance over a range of wavelength. The results of our paper show that a lowest effective reflectivity could be achieved for the optimized cone-shaped SWS as compared to hemisphere-, parabola-, and cylinder-shaped structures with the same volume. The best shape SWS is then fabricated together with a silicon (Si) solar cell, and the efficiency of the solar cell is compared with that of a solar cell with single-layer antireflection coating (ARC). An increase of 1.09% in cell efficiency (η) is observed for the Si solar cell with a cone-shaped Si ₃N₄ SWS (η = 12.86%) as compared with the cell with single-layer Si₃N₄ ARCs (η = 11.77%).