Circular Nanocavity in Ultrathin c-Si Solar Cell for Efficient Light Absorption

In this work, the effect of circular nanocavity on light trapping in a c-Si solar cell was studied by finite difference time domain (FDTD) simulation. The structure of the solar cell was considered to be Si₃N₄/c-Si/Ag, where the Ag layer was pattered and conformal growth of Si and Si₃N₄ was considered. The absorption spectra in the thin Si layer were determined and found 40 times higher at the infrared region (beyond 800 nm). For qualitative analysis, the short-circuit current of the solar cell was determined computationally by AM 1.5G solar illumination and found to be 2.1 times higher in the case of nanocavity as that compared to un-patterned solar cell. The enhancement in absorption in the solar cell is attributed to the different plasmonic modes coupled in the thin c-Si layer. The incident angle-dependent study was performed to observe the effect on enhancement in wide-angle incidence. The thickness-dependent study confirms 2.1 to 1.75 times enhancement in short-circuit current in 100- to 250-nm-thick c-Si layer. Therefore, this observation suggests that this structure has good prospect in achieving high conversion efficiency while reducing the device cost.