Numerical Study on Overcoming the Light-Harvesting Limitation of Lead-Free Cs₂AgBiBr₆ Double Perovskite Solar Cell...

Lead-free Cs₂AgBiBr₆ double perovskite has emerged as a promising new-generation photovoltaic, due to its non-toxicity, long carrier lifetime, and low exciton binding energies. However, the low power conversion efficiency, due to the high indirect bandgap (≈2 eV), is a challenge that must be overcome and acts as an obstacle to commercialization. Herein, to overcome the limitations through the light trapping strategy, we analyzed the performance evaluation via FDTD simulation when applying the moth-eye broadband antireflection (AR) layer on top of a Cs₂AgBiBr₆ double perovskite cell. A parabola cone structure was used as a moth-eye AR layer, and an Al₂O₃ (n: 1.77), MgF₂ (n: 1.38), SiO₂ (n: 1.46), and ZnO (n: 1.9) were selected as investigation targets. The simulation was performed assuming that the IQE was 100% and when the heights of Al₂O₃, MgF₂, SiO₂, and ZnO were 500, 350, 250, and 450 nm, which are the optimal conditions, respectively, the maximum short-circuit current density improved 41, 46, 11.7, and 15%, respectively, compared to the reference cell. This study is meaningful and innovative in analyzing how the refractive index of a moth-eye antireflection layer affects the light trapping within the cell under broadband illumination until the NIR region.