Photonic Crystal Beam Splitter Electrode in Kesterite Tandem Solar Cells: A Numerical Approach

The majority of numerical research on kesterite tandem solar cells has predominantly focused on a two‐terminal (2T) configuration that utilizes an ideal tunnel junction. Herein, the performance of kesterite tandem solar cells by introducing a photonic crystal structure (1DPC) as intermediate layer in both three‐terminal (3T) and four‐terminal (4T) configurations is investigated. The photonic crystal (1DPC) is designed by stacking ITO and SiO2 layers with the terminal layer consisting of NiO. Optical properties of the 1DPC are modeled. This innovative approach offers several advantages. 1) The 1DPC selectively reflects lower wavelengths, effectively enhancing the short‐circuit current density (Jsc) of the top subcell, while the solar irradiance spectrum at higher‐wavelength optimum for the subcell is not affected. 2) The 1DPC serves as an intermediate electrode, needed for the 3T or 4T configuration. 3) Replacing the conventional Mo back contact with a NiO layer significantly boosts the open‐circuit voltage (Voc) of the top subcell. The findings demonstrate that these configurations exhibit higher performance compared to previously reported results. Furthermore, the utilization of 3T and 4T configurations, incorporating the 1DPC as an electrical beam splitter, provides an effective and accurate design compared to the 2T configuration using ideal tunnel junctions. This study explores the performance of kesterite tandem solar cells, focusing on three‐terminal (3T) and four‐terminal (4T) configurations using a photonic crystal (1DPC) as an intermediate layer with double functionality: electrode and beam splitter. The 1DPC selectively enhances Jsc in the top subcell without affecting the optimum solar irradiance incoming on the bottom subcell.