Bandgap Engineering and Enhancing Optoelectronic Performance of a Lead-Free Double Perovskite Cs₂AgBiBr₆ Solar Cell...

In this study, solar cells based on pure Cs₂AgBiBr₆ and Al-doped metal were fabricated using the sol-gel spin-coating technique. X-ray diffraction (XRD) analysis confirmed the formation of cubic-structured films for both pure and Al-doped. Notably, the grain size of Al-doped Cs₂AgBiBr₆ was observed to be larger than that of its pure counterpart. The optical properties of these films were investigated using UV-vis spectroscopy, revealing essential parameters such as the bandgap energy (E_g), refractive index (n), extinction coefficients (k), and dielectric constant. While the pure film exhibited an E_g of 1.91 eV, the Al-doped film demonstrated a slightly lower E_g of 1.82 eV. Utilization of these films in solar cell fabrication yielded intriguing results. The J-V curve shows that the pure solar cell displayed a short-circuit current density (J_sc) of 5.01 mA/cm², a fill factor (FF) of 0.67, an open-circuit voltage (V_oc) of 0.89 V, and an efficiency of 3.02%. Al doping led to improvements, with an increase in V_oc to 0.91 V, FF to 0.71, and J_sc to 5.29 mA/cm². Consequently, the overall efficiency surged to 3.40%, marking a substantial 12.5% enhancement compared with the pure solar cell. These findings underscore the efficacy of Al doping in enhancing the performance of Cs₂AgBiBr₆-based solar cells.